NEET Biology

NEET Biology Kingdom Monera Main features

It encompasses all prokaryotic species, with size ranges of 1-10 µm, including cyanobacteria (blue-green algae) and bacteria.

• Prokaryotic cells are distinguished from eukaryotic cells by possessing a cell wall composed of complex substances (excluding cellulose and chitin), circular bare DNA, and the absence of membrane-bound organelles such as mitochondria.
• Some prokaryotes possess internal membranes, such as lysosomes in certain bacteria, and membrane systems that house enzymes for photosynthesis and respiration.
• Prokaryotes reproduce via binary fission.
• Cyanobacteria do not exhibit sexual reproduction; rather, genetic recombination in certain bacteria transpires through conjugation, transformation, and transduction.
• Numerous prokaryotes produce spores in response to unfavorable conditions.

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• Their small size, metabolic diversity, and rapid reproduction probably account for the evolutionary success of prokaryotes.
• Classification of Kingdom Monera. Simple prokaryotic cell structure, unicellular, both heterotrophs and autotrophs. Kingdom Monera was created by Copeland (1966), and divided into three main groups.
• Schizomycophyta (Bacteria) smallest living cells, basically unicellular, with indistinct nuclei, colorless, and mainly heterotrophic Examples; are Cocci, Vibrio, Bacilli, Spirilla.
• Cyanophyta or Cyanobacteria (Blue-green algae). Unicellular, no distinct nucleus, blue-green color e.g. Oscillatoria, Nostoc, Gloeoccipsa, Tolypothrix.
• Archaebacteria. Most primitive prokaryotes are considered to evolve immediately after the evolution of first life, The cell wall lacks peptidoglycan but contains protein and non-cellulosic polysaccharides. Branched-chain lipids in membrane. Live under hostile conditions Example; Methanogens, Halophiles, and Thermoacidophiles.

Kingdom Monera NEET Notes

NEET Biology Kingdom Monera Bacteria

• Bacteria are very small and their size generally ranges from 0.2 – 1.5 pm in diameter and 2 – 10, pm in length.
• Dialister pneumonsinilis is the smallest bacterium (0.15 — 0. 3 pm long); Bacillus buischili (80 pm long, 3 — 6 pm, diameter); Beggiatoa mirabilis is the largest bacterium (16 — 45pm diameter and upto several centimetres long).
• Bacteria occur in three basic forms or shapes. These are either spherical (cocci), rod-shaped (bacilli), or spiral (vibrio/spirillum). Though most bacterial species have cells that are of a fairly constant and characteristic shape, some species are pleomorphic (i.e.; these can exhibit a variety of shapes).
• Gram staining, introduced by Christian Gram in 1884, divides bacteria into two groups: Gram-positive and Gram-negative.
• Flagella (sing, flagellum; Latin whip). Long (3 — 12 pm), fine, wavy, filamentous appendages that protrude through the cell wall, responsible for the motility of bacteria.
• These are much thinner than the flagella or cilia of eukaryotes, being 0.01 to 0.02 pm in diameter.
• Bacteria may be atrichous (without flagella), monotrichous (with one flagellum), lophotrichous (with a group of flagella at one end), amphitrichous.
• Two flagella (also two groups of Flagella), one at each end Example; Alkaligenes feces and peritrichous (flagella present all over the body) ccphalotrichous—(Two or more flagella at one end)
• Pili or Fimbriae (Sings. Pilus = hair fimbirae = fringe). These are hollow, nonhelical, filamentous appendages projecting from the walls of some gram-negative bacteria.
• These are thinner and shorter; and more numerous than the flagella. These also arise from the basal body and are made up of specific proteins called pilin.
• Some bacterial cells are surrounded by a viscous substance forming a covering layer or envelope around the cell wall. If this layer is in the form of a loose mass, it is called slime.
• Below the external structures like capsules and flagella; and outside the cell membrane is present a rigid structure called a cell wall. Due to its rigidity, it protects the internal structures of the cell and provides shape to the cell.
• However, its main function is to prevent the cell from expanding and bursting (Most bacteria live in hypotonic environments, and are likely to take in much water and eventually burst).
• The cell walls of almost all the eubacteria (true bacteria) are made up of peptidoglycan, also called murein or mucopeptidc. It is found only in monerans.
• The plasma membrane is a phospholipid membrane also containing proteins and polysaccharides. It is selectively permeable. The respiratory enzymes are associated with the cell membrane as the mitochondria are absent.
• Mesosomes. The cytoplasmic membrane is invaginated at certain places into the cytoplasm in the form of the system of convoluted tubules and vesicles, (mesosomes).
• On their surface are found enzymes associated with respiration. Therefore, these are supposed to be analogous to the mitochondria of eukaryotes.
• The cytoplasm is a complex mixture of amino acids, proteins, lipo-complexes, nucleotides, carbohydrates, vitamins, and coenzymes.
• The membrane-bounded organelles like endoplasmic reticulum, mitochondria, and Golgi bodies are absent in bacteria. However, ribosomes are present in sizeable numbers, providing a granular appearance to the cytoplasm.
• The cytoplasm contains about 10,000—30,000 ribosomes of the 70 S type. The sedimentation coefficient of bacterial ribosomes is 70S. Each ribosome consists of 2 unequal subunits (30S and 50S). Each subunit is composed of RNA and protein.
• The most common non-living inclusions in the cytoplasm are —volutin granules, PHB, and elemental sulfur. The volutin granules, also known as metachromatic granules, are polymetaphosphates and serve as a reserve source of phosphate.
• PHB. (Poly (3 hydroxybutyrate) is a lipid-like material and can serve as a reserve carbon and energy source.
• Some bacteria that live in aquatic habitats form gas vacuoles which provide buoyancy to the cells.
• As compared to the eukaryotes, bacteria do not contain a distinct membrane-bounded nucleus and all other membrane-bound organelles are absent.
• However, an amorphous lobular mass of fibrillar, chromatin-type material that occupies about 10 — 20% of the cell, is present near the center of the cell.
• DNA of the cell is confined to this area called nucleoid or chromatin body or nuclear equivalent or genophore.
• It is also called a bacterial chromosome as it consists of a single, circular DNA molecule in which all the genes are linked.
• This single molecule is over a thousand times longer than the cell itself and is, therefore, highly folded. Bacteria generally lack the histone proteins.
• In addition to the normal DNA chromosome, some extrachromosomal genetic elements are often found in bacteria. These elements are called plasmids.
• These are circular pieces of DNA that have extra genes. These are capable of autonomous replication in the cytoplasm of the bacterial cell.
• Plasmids carry genes responsible for different functions in bacteria. For example, Rfactor plasmids (which confer resistance to antibiotics), colicincrgic factors (responsible for the formation, in coli. of special proteins that kill closely related species of bacteria) of genes (for nitrogen fixation).

Reproduction

It takes place by binary fission with the cell dividing at right angles to its long axis. The following steps are involved:

1. Division of nuclear material. After the bacterial cell has attained maximum size, the nuclear material duplicates and divides without any spindle formation. The DNA is found attached to the mesosomes near the septum-forming region.
2. Cleavage of the cytoplasm. The cell membrane from the middle part of the cell grows inwards dividing the cytoplasm into two halves.
3. Formation of cross wall. In between the two newly formed cytoplasmic membranes, a cell wall (septum) is laid down, forming two daughter cells.
4. Separation of daughter cells. The growth of the two daughter cells creates tension that separates the two newly formed cells.

Bacteria Classification NEET Exam

Transfer of genetic material (Genetic recombination) 

1. Conjugation. Investigations with an electron microscope have shown that two E. coli cells can conjugate and the genetic material (DNA) from one cell can be transferred to the other. The sex difference between the Z (donor) and Z (Recipient) cells is determined by the presence or absence of a specific genetic factor called F (fertility factor. When present, F is a donor cell, and when absent, F-, is a recipient cell. The F factor can exist in two alternative states—as part of the E. coli chromosome or as a very small free DNA strand.
   • The £. coli strains are then (high-frequency of recombination) or metafile and F strains respectively.
   • Conjugation occurs between an Hfr and a cell or between a P and a Pcell. The P cells transfer only the F factors after its replication.
   • The cells transfer both the F factor as well as the genetic constitution of the donor cell. The recipient cell now becomes a merozygote (partially diploid).
2. Transformation. A genetic change takes place in the recipient bacterial cell as a result of the absorption of DNA fragments reduced
3. Transduction. It is a process in which fragments of UNA are carried by bacteriophages train one bacterial cell to another. It was first observed by Zander and Lederherg (1952).

NEET Biology Kingdom Monera Economic Importance Of Bacteria

Cyanobacteria Characteristics NEET

NEET Biology Kingdom Monera Actinomycetes

These microorganisms connect bacteria with fungus. Similar to mushrooms, their somatic architecture comprises multicellular filaments (hyphae) that collectively constitute the mycelium.

• They were previously referred to as “Ray Fungi.” They generate asexual spores, referred to as conidia, on aerial hyphae, which serve as asexual spores in fungi, in contrast to bacterial endospores.
• They are thermally inactivated and not thermally resistant. Their spores and cells do not exceed 2 to 3 microns in diameter.
• Actinomycetes are either saprophytes or parasites. Certain organisms, such as Streptomyces spp., thrive in the soil.
• Conversely, several species, such as Micromonospora spp., are only located in semi-aquatic environments, specifically among lacustrine muds.
• Certain members, like as Nocardici spp., are recognized for their ability to breakdown substrates including paraffin, phenol, and petroleum-derived compounds, which are very resistant to most bacteria.
• Actinomycetes spp. are specialist parasites located in the oral cavities of animals. Reproduction through fragmentation or conidia.

Archaebacteria Features NEET Study Material

Economic Importance

The genus streptomyces of this group is most important, some species of which produce antibiotic substances of great medicinal value like streptomycin, chlorotetracycline, oxytetracycline, tetracycline, chloramphenicol, and erythromycin.

NEET Biology Kingdom Monera Chlamydiae

These are the smallest recognized bacteria and are subgroups of rickettsiae which cause diseases in humans and animals. They have DNA, RNA, and some enzymes. They can be treated with some antibiotics.

The two species of chlamydiae are:

Chlamydia trachomatis causes trachoma in the eyes and two sexually transmitted diseases such as chlamydial urethritis and lymphogranuloma encrust.

Chlamydia psittaci which causes psittacosis in birds. L-forms. Klieneberger discovered L-forms during the culture of Streptobacillus moniliformis.

being the initial of the Lister Institute named for Lord Lister (a pioneer in aseptic surgery). These micro-organisms lack cell walls and are produced only by Bacillus.

L-forms can be converted again into Strcp-tobacilliis. L-forms can be selected by cultivation of bacteria in an osmotically buffered penicillin-containing medium.

Therefore, L-forms arc bacteria in which the primer for peptidoglycan has either been eliminated or modified by penicillin treatment.

They are found in water and mud as free-living organisms. They form a small group of heterotrophic bacteria. Most of the spirochaetes are parasites of man and animals.

They are unicellular and helicoid in shape. The cell has two overlapping sets of fibrils.

The protoplasm is enclosed by a flexible cell wall.

Spirochaetes cause some human diseases as Syphilis is caused by Treponema pallidum Relapsing fever by Borrelia Jaundice (infectious) by Leptospira

NEET Biology Kingdom Monera Archaebacteria (Ancient Bacteria)

They are highly primitive and inhabit exceedingly inhospitable environments where few other species can endure.

• Certain organisms are anaerobic and generate methane, while others inhabit highly saline environments or thrive in hot, acidic sulfur springs.
• Their cell wall lacks peptidoglycan.
• They have special branched-chain lipids in their cell walls which make them heat and acid resistant.

Differences between cyanobacteria, halophiles, and thermoacidophiles

Gram-Positive vs Gram-Negative Bacteria NEET

Differences between Gran +ve and Gram -ve bacteria

Prokaryotic Cell Structure NEET Biology

• Mirco-organisms like bacteria sometimes can exist without a cell wall. The hu-cell membrane and its intact contents are then called protoplasts (osmotically fragile). Young actively growing gram (+) bacteria are sensitive to penicillin. So. these bacteria can Be made of protoplasts.
• The nrehacbactcria and bacteria possibly arose from a more ancient form of life called progenitor. Understanding one kind of organism requires the isolation of one individual and multiplying or culturing it. i.e. to obtain pure culture.
• A pure culture contains multiple copies of a single kind of micro-organism. The microbiologist has developed several techniques to obtain the pure culture of microorganisms.
• All eubacteria have a cell wall, made up ofmurein or peptidoglycan. It consists of polysaccharides cross-linked with short amino acid chains. Bacterial conjugation though different from eukaryotic sexual reproduction is a means of making new genetic combinations that are expressed as progeny.
• Rhizobium is a symbiotic nitrogen-fixing bacterium. The non-symbiotic free living nitrogen-fixing bacteria are Azotobacter, Beijerinckia, and Klebsiella (all aerobic) The non-symbiotic free living anaerobe, nitrogen-fixing bacterium is Clostridium pasteurianitm.
• Chromalium. Rhodospirillum arc photosynthetic nitrogen-fixing bacteria. E. coli bacteria are present in the large intestine of humans and mammals. They are straight rods. There are motile and non-motile types of E.coli.
• The cell surface has pili on which certain phages are absorbed. E. coli is a facultative anaerobe. The optimum temperature for its growth is 30-37 °C and the optimum pH value of medium is 7.2— ca> 7.5.
• Nosloc sp. occurs within the tlialli of Blasia and Anthoceros (The Bryophytes). Nostoc sp. lives within the cells of Gcosiphon pyreforme (a fungus) Nostoc sp. occurs in the petiole of Gunnera (an angiosperm). Calothrix sp. lives within the cells of Enteromorpha (a green alga).
• Trifolium alexandrinum (Clover) contains Nostoc in its nodules. The reddish color of the Red Sea is due to a cyanobacterium Trichodesmium erythraeum.
• Cyanobacteria associated with Protista. Death factors VFDF (very fast). FDF (fast) and SDF (slow) are toxins produced by cyanobacteria. Biological nitrogen fixation has been discovered by Winogradsky.

• The smallest cocci range from 0.5 pm to 1.5. pm in diameter while spiriJJi are as large as 60pm (Peberdy, 1980). About one trillion (1 012) bacteria of average size could be packed into a 1 ml pipette.
• A single drop of water may contain as many as 50 thousand million bacteria. A teaspoonful (5 ml.) of packed bacteria represents 2000 times as many individuals as there are people on Earth.
• A tea .spoon of rich soil contains billions of bacteria Mycobacterium and Xanthomonas form nodules in the leaves of Ardisia and Puvetta while Frankia forms nodules in the roots of Alms and Casuarina.
• Gram-negative bacteria are usually partly or wholly resistant to penicillin.
• When Gram-positive bacteria are treated with lysozyme (found in egg white, secretion of skin and mucous membranes and tears) they are rapidly denuded of their cell walls and become naked protoplasts while the peptidoglycan cell wall of Gram-negative bacteria is protected by an outer layer of lipo-complex (it can be removed by ethylene diamine tetra acetate or EDTA).
• So the cell wall of Gram (—) bacteria is not completely re¬ moved. Such only partially denuded cells are called spheroplasts.
• The cell walls of Gram-positive and Gram-negative bacteria differ in their chemical composition. In Gram-positive bacteria, the cell wall has a thick peptidoglycan layer that comprises 90 percent of the cell wall.
• The cell walls of gram-negative bacteria are much more complex. The peptidoglycan layer is very thin making up only 10% or less of the cell wall.
• However, the most interesting feature is the presence of an outer membrane that covers a thin underlying layer of peptidoglycan. The outer membrane is a bi-layered structure consisting chiefly of phospholipids, proteins, and lipopolysaccharides (LPS).
• Due to the presence of the outer membrane, Gram nega¬ tive bacteria are rich in lipids that make up about 11-12% of the dry weight of the wall. Teichoic acid is absent.
• The cells of certain bacteria like Aquaspirillum magnetotacticum contain structures composed of iron in the form of magnetite (Fe304). These are called magnetosomes and help bacteria orient themselves along the geomagnetic lines.

Cyanobacteria Blue-Green Algae For NEET Biology

Kail V. Non-Nncgcll distinguished blue preen algae from algae. Name k Aihku ten was given by Klilin nml Morris

Blue-Green Algae Main Features

1. Common forms include unicellular, colonial, filamentous, heterotrichous, Gram-variable, and photosynthetic.
2. The cell wall features an external layer that is gelatinous, viscous, and mucilaginous.
3. The cellular contents are partitioned into two regions: the outer chromatograms containing photosynthetic pigments and the inner colorless cytoplasm.
4. The cell wall consists of two layers, with the inner layer composed of peptidoglycan or mucopolysaccharides derived from amino sugars

Example: Glucosamine and amino acids

Example: Muramic acid and diaminopimelic acid

• Bacteria and cyanobacteria lack mitochondria, genuine vacuoles, and endoplasmic reticulum.
• Hormocyst. Thick-walled hormogonia or multicellular akinetes present in cyanobacteria.
• Sterols are nonexistent in both bacteria and cyanobacteria.
• No membrane-bound chloroplasts or photosynthetic lamellae, such as thylakoid arcs, are typically found in the peripheral cytoplasm.
• The authentic nucleus is lacking. Delicate DNA fibrils are either dispersed throughout the cell or concentrated in the central region. Its chromosome is analogous to a bacterial chromosome.
• Cyanobacteria lack distinct reproductive organs, sexual reproduction, and motile reproductive structures.
• Gas vacuoles are frequently found to modulate buoyancy in aquatic environments.
• Cyanobacteria inhabit nearly all aquatic habitats. The organisms inhabit tropical regions, plains, and are found in soil, freshwater, and marine environments.
• They constitute a component of plankton in lakes and oceans. Certain cyanobacteria inhabit the frigid waters of glaciers, while others thrive in hot springs with temperatures exceeding 85°C.
• Certain blue-green algae exist as symbionts with other organisms. For instance, they frequently constitute the algal components of lichens.

Blue-green Algae NEET Notes

Shapes of Cyanobacteria

Cyanobacteria may be unicellular, colonial, or filamentous. Unicellular forms have single-celled body Examples Synecliococcus, Chroococcus, and Anacystis.

The colonial forms are of two types:

• Dendroid. They are the forms of cyanobacteria in which cells are held together by gelatinous connections example Chamae-siphon.
• Coccoid. They tire unicellular cyanobacteria embedded in a common matrix of mucilage without gelatinous connections, Example Microcystis. Filamentous forms are thread-like multicellular strands in which each filament or strand consists of a sheath of mucilage and one or more cellular strands called trichomes.
• Spirulina has a spirally coiled filament while a branched filament is found in Hapalosiphon.

Filaments that have single trichomes are divided into two types:

1. Homocystous. They have undifferentiated trichomes Example; Oscillatoria and Arthrospira.
2. Heterocystous. They have differentiated trichomes, for Example; Nostoc, and Rivularia.

In Schizothrix more than one trichomes are found in the same sheath of a filament. In Stigonema, a filament may have a few or a multiseriate trichome (in which numerous filaments are associated in a common sheath).

Classification based on morphology, motility, reproduction, and capacity of N2 fixation Cohen Bazire classified cyanobacteria into four groups:

1. Chroococcacean. Examples; Microcystis, Chroococcus, Gloeocapsa, etc.
2. Pseudocapsalean. Example Democarpa
3. Oscillatorian. Example; Oscillatoria.
4. Heterocystous. Examples; Nostoc, Aiiabacita, etc.
5. Among these groups, only Heterocystous has nitrogen-fixing capacity

Cyanobacteria Characteristics NEET Biology

Economic Importance of Cyanobacteria

1. Useful activities.
   1. Nitrogen fixation is done by about 50 species of cyanobacteria. Based on nitrogen fixation there are two types:
   2. Free-living nitrogen-fixing cyanobacteria, for Example, Anahaeiui, Nostoc, Aulosira, Stylonenui, Stigonema, Oleotricltia, Calotlirix, TolypotlirLx, etc.
   3. They can fix approximately 15-48 kg of nitrogen per hectare per season. Aulosirafertilissima is the most active nitrogen fixer in Rice fields.
   4. Cslindnvpcrmum is an active nitrogen fixer of Sugarcane and Maize fields.
   5. Tolyptthrix is used as a nitrogen fixer in experimental fields. (hi Symbiotic nitrogen-fixing cyanobacteria: Anabaena and Nostoc species are common symbionts in lichens. Anihoceros, Azolla, and Cycas roots in which it can fix nitrogen.
   6. Azolla pinnata has Anabaena azollac in its fronds which is often inoculated to Rice fields for nitrogen fixation.
   7. They provide food for fish and other aquatic animals but Spirulina is regularly collected for human consumption in parts of Africa and India (from Samber Lake of Rajasthani. Nostoc in China, Anabaena in India.
   8. They provide suitable conditions for the growth of other organisms in a hostile environment.
   9. They are used as biofertilizers.
   10. Anabaena and Aulosira do not allow mosquito larvae to grow.
   11. They improve the physical texture of the soil.
2. Harmful activities
   1. Microcystis secretes hydroxylamine which kills aquatic life, birds, and cattle while Anabaena causes gastric trouble in domesticated animals by contaminating the drinking water of these animals.
   2. Microcystis aeruginosa (= Anacystis cyanea), Anabaena flosaquae and Aphanizoinenon flosaquae not only spoil the taste of drinking water but are also toxic to human beings.
   3. They cause depletion of supply to aquatic animals by the formation of blood by Microcystis, Anabaena, and Nostoc.
   4. Anacystis causes corrosion of metallic water pipes.
   5. The growth of algae is controlled by using algicides such as dichlorophen, phylon XI, exalgae, cushion, etc.

Mycoplasma

Cell walls are absent in the simplest and smallest free-living prokaryotes, which are frequently referred to as MLOs (Mycoplasma-like organisms) or PPLOs (Pleuropneumonia-like organisms).

• They are referred to as the “Jokers of the plant kingdom.”Mycoplasma gallispticum is the smallest prokaryote, measuring 0.3 to 0.5 m in size. The following were identified by Roux and Nocard in 1898.
• Nutritionally heterotrophic. Pleuropneumonia is produced in domestic animals, while Witch’s broom is produced in plants.
• Mycoplasma sensitivity. Mycoplasma is a gram-negative bacterium. Penicillin is ineffective against them; however, they are susceptible to other antibiotics, including streptomycin, chloramphenicol, and erythromycin.
• Their resistance to penicillin (and other antibiotics of the same class) may be attributed to the absence of a cell wall.
• This antibiotic disrupts the synthesis of peptidoglycan, a critical component of the bacterial cell wall.
• Reproduction. There is a lack of knowledge regarding mycoplasma reproduction.

However, four types of cellular bodies of Mycoplasma laidlawii have been found. These are:

1. Elementary bodies
2. Secondary bodies
3. Tertiary cell bodies and
4. Quaternary bodies

Elementary bodies reproduce by a process like budding. These grow in size and then again give rise to elementary bodies. In some cases, mycoplasma may reproduce by binary fission. Economic Importance Mycoplasma are always harmful and cause diseases in plants and animals.

Plant diseases. Many plant diseases caused by mycoplasma were earlier considered to be viral diseases before 1967. Since 1967 most of the plant diseases of the yellow group have been reported to be caused by mycoplasma.

These diseases are Little leaf of brinjal Citrus greening Sandal spike Grassy shoot of sugarcane Rice yellow dwarf Colton little leaf or cotton stenosis Sesamum phyllody and several others like Bunty top of papaya Aster yellows.

Role Of Cyanobacteria In Nitrogen Fixation NEET

Potato witch’s

• Pathologies in animals. Mycoplasma is responsible for diseases such as arthritis, various respiratory illnesses, and primary atypical pneumonia (PAP). Mycoplasma liowinis and M.fcrmcntans, among others, are believed to induce infertility in human males.
• In 1909, Howard Taylor Rickets identified novel microbes in the blood of individuals afflicted with Rocky Mountain spotted fever.
• This organism and others of its kind were designated as Rickettsiae, which are today classified as a category of bacteria. The designation Rickettsiae was conferred to pay tribute to the discoverer.

Rickettsiae differ from bacteria in having:

1. Smaller sizes with smaller genomes provide fewer enzymes. Requirement of an exogenous energy supplier for growth.
2. These organisms exist in alternate shapes and hence they are pleomorphic. They have no flagella, pili, capsules, or spores.
3. The cell wall is chemically similar to Gram (-) bacteria, The cytoplasm of Rickettsiae contains both DNA, RNA, and some enzymes.
4. Reproduction is by binary fission. Rickettsial infections usually respond to treatment with tetracyclines or chloramphenicol.

NEET Biology Sense Organs

• Environmental information received by a sense organ is first changed into the language of the nervous system and the process is called transduction.
• Stimuli are perceived by receptors but interpretation of the stimuli is done by specific nervous centres in the brain. Receptors may be exteroreceptors, proprioreceptors or interoreceptors. Exteroreceptors are present in special sense organs like skin, nasal chamber, taste buds, eyes and ears.
• The five kinds of sensory receptors are mechanoreceptors which respond to physical deformations of tissues; chemoreceptors which respond to certain molecules dissolved in solution; thermoreceptors which respond to heat; and painreceptors which respond to excess heat, pressure, or certain chemicals; and electromagnetic which respond to energy of different wavelengths.
• Sensory receptors can also be categorized as exteroreceptors which receive information from the external environment; interoreceptors which receive information from the internal environment; and proprioreceptors which receive information about the body’s orientation in space.
• Skin receptors may be naked free nerve endings or covered bulbs or corpuscles. These may be tango receptors, thermoreceptors, algesia receptors etc.

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Principles Of Inheritance And Variation Neet Notes

NEET Biology Sense Of Smell

Olfactoreceptors are present in the olfactory epithelium and are chemoreceptors to specific odours. These show olfactory adaptation as are soon fatigued when exposed to specific odour for a long period.

Evolution Neet Notes

In the case of humans 7 groups of primary odours have been classified :

1. Camphoraceous (Scent of camphor)
2. Musky ( scent of musk )
3. Floral (flowers)
4. Pepperminty ( Scent of oil or peppermint)
5. Ethereal ( Scent of ether)
6. Pungent (Scent of spices)
7. Putrid ( Decaying meat)

NEET Biology Sense Taste Receptors

1. Gustatoreceptors are present in taste buds on the tongue. These are also chemoreceptors. Man can perceive four basic modalities of taste with the help of different taste buds located on different parts of the tongue.
2. Human beings recognise four basic modalities of taste, viz. sweet, sour, salty and bitter. Sweet, sour, salty and bitter tastes are principally perceived at the tip, along the lateral edges, on the upper side of the front half, and the back of the tongue respectively.
3. The taste of food is of vital importance in the process of digestion because taste stimulates reflexes causing secretions of saliva, gastric juice and pancreatic juice.

Rheo Receptors. They are responsible for perceiving water currents. They are of four types.

1. Lateral line sense organs
2. Scattered pit organs
3. Ampulla of Lorenzini
4. Vesicles of Sair
5. Watering of eyes due to gases or smoke is due to irritoreceptors.

Principles Of Inheritance And Variation Neet Notes

NEET Biology Sense The Eye

The eye captures light reflected from objects in the visual field and transforms it into electrical signals, which the brain interprets as visual perception.

• Light is emitted and absorbed in distinct quanta of photons. It propagates as waves of electromagnetic radiation, with wavelengths perceptible to the human eye ranging from 380 to 760 nm, and is most sensitive at 500 nm (i.e., green color).
• Free-living animals require photoreception to identify food, predators, and refuge. Photoreceptors have evolved for this purpose, undergoing progressive improvement over time.
• Planarians (flatworms) possess a “eye cup” that functions as a photosensory organ to perceive light intensity and direction.
• In annelids (polychaetes) and subsequent higher animals, the eye has evolved into a distinct organ.
• In insects and crustaceans, the compound eye consists of individual units known as ommatidia. They are adapted for apposition (mosaic) vision in bright illumination and superposition imagery in low light (darkness).
• It additionally produces colored visuals. Honeybees possess the ability to perceive ultraviolet energy.
• Among all invertebrates, only cephalopods (molluscs) possess eyes with real lenses like to those of vertebrates.

NEET Biology Sense Human (Mammalian) Eye

1. A fluid-filled ball with about 21 mm (17.5 mm just born) metro-posterior diameter (optical or visual avis) lodged in the bony orbit of sphenoid bone with a cushion of fat.
2. It weighs about 7 gin.
3. About 1/6 of the eyeball (l/3rd in frog and 1/5 in rabbit) projects outside while the rest parts remain within the socket. 1 Iris anterior part is covered with transparent cornea.
4. Each eye is protected by upper and lower eyelids with eyelashes.
5. The eyes are somewhat ball-like and are lodged in the deep skull cavities (orbits). The clevis can rapidly close to prevent dust or other things from entering the eyes. The eyelashes also help in this function. On any irritation, due to a fallen particle due to gas or smoke or under certain emotions, the eyes are flooded with a watery secretion or tears.
6. This secretion comes in front of the (car glands, located near the outer border of each eye and it is poured through minute ducts on the inner surface of the upper eyelid. Movements of the upper eyelid spread the secretion over the eye to wash off any dirt.

Structure. The wall of each eye is made of the three concentric layers sclerotic, choroid and retina. In the front, the sclerotic layer forms a transparent, somewhat bulging circular comea.

1. The cornea can be stored and grafted on the other person. The cornea and the rest of the exposed sclerotic layer are covered by another very thin transparent membrane, the conjunctiva, which is the continuation of the inner surface of the eyelids.
2. The pigmented iris, formed by the middle or choroid layer encloses the pupil, visible from outside as a dark window. The iris consists of delicate muscles which regulate the size of the pupil and consequently control the amount of light passing to the retina ciliary body.
3. Just behind the pupil lies a biconvex lens which is held in position by ligaments and muscles. A transparent watery fluid (aqueous humour) fills the narrow space between the lens and the comea. The large chamber behind the lens is filled with a clear, gelatinous substance (vitreous humour).
4. The sensory layer called the retina, consists of two types of cells, rods and cones. The rods are sensitive to dim light and do not distinguish colours, whereas the cone cells are sensitive to bright light and can distinguish colours.
5. The cone cells are most numerous near the back of the eye, opposite the pupil. This part is somewhat depressed and is known as the yellow spot or fovea. Vision is the sharpest here. The sensory fibres from the retina bundle together and emerge from the back of the eyeball as the optic nerve.
6. At the exit of the optic nerve, there are no rods or cones. The part of the image falling at this place is not perceived, and so this place is called the blind spot.

Principles Of Inheritance And Variation Neet Notes

NEET Biology Sense Associated Glands

1. Lacrimal gland (tear gland).Consists of a chain of three small glands located at the outer angle of each eye. Tear flows into the lacrimal duct through the small pore, and lacrimal punctum to pass into the nasal chamber of its side.

• Tear is a salty fluid, that contains amino acids, glucose and lysozyme.
• A continuous layer of tear is always present upon the comea to keep it moist, and away from dust and other foreign particles. It also nourishes comea and acts as a medium for refraction of light; lysozyme in it is antibacterial.
• In humans tear secretion begins at four months of birth.
• Tearing is stimulated by injury, irritation, emotions etc.

1. The meibomian gland (tarsal gland) is a modified sebaceous gland located on the mar¬gin of eyelids. Its oily secretion makes a film over the tear to prevent it1 fall from the surface of comea.
2. The Zeis gland is also a modified sebaceous gland in the hair follicle of eyelashes to keep them smooth and waterproof by its oily secretion.
3. Glands of Moll are modified sweat glands on the inner surface of eyelids found only in humans, of uncertain function.
4. Harderian Gland. It is a special type of mucous-secreting gland found in aquatic, fossorial and bush dwellers. Mucous keeps the eye moist and protected from abrasion. In frogs it remains beneath the lower eyelid towards the inner corner of the eye, also found in all reptiles and aquatic mammals, rabbits etc., but absent in man. Its secretion is known as crocodile tears.

Evolution Neet Notes

NEET Biology Sense Refraction Or Focusing

Tear → conjunctiva → cornea → aqueous humor → lens → vitreous humor refract light rays to converge on the retina.

• The cornea exhibits the highest degree of refraction, followed by the lens.
• The lens precisely directs the beam onto the retina to create a picture. Accommodation is achieved by altering the curvature (convexity) of the lens through the action of ciliary muscles, depending on the object’s distance.
• When the ciliary muscle is relaxed, the eye remains at rest and focuses on distant things. To focus on nearby objects, the ciliary muscle contracts to enhance the lens’s convexity.
• The frog possesses inadequate accommodation capabilities; it is hypermetropic in water and myopic on land. Nevertheless, a minor adjustment can be achieved by moving the lens anteriorly and posteriorly, akin to a camera.
• The inverted virtual image is produced on the retina, and normal vision is referred to as emmetropic.
• In humans, each eye possesses a vision field of around 170°. The significant overlap of visual fields aids in assessing the relative positions of objects, constituting depth awareness or stereoscopic vision.
• The typical range of vision in the human eye extends from 30 centimeters to 6 meters.

Evolution Neet Notes

NEET Biology Sense Common Defects Of Eye

1. Myopia (Near-sightedness). When the image of a distant object is focussed in front of the retina due to lengthening of the eyeball or due to increased convexity of the lens. It can be corrected by using appropriate concave lenses.
2. Hypermetropia or Far-sightedness. It is due to just the opposite condition as in myopia. It can be corrected by wearing suitable convex lenses.
3. Astigmatism. It is due to an error in the shape of the lens and cornea, as they are of different curvatures. Cylindrical glasses are used to correct this defect.
4. Presbyopia (old age sight). It is the diminished ability to focus the eye on near objects due to the gradual loss of elasticity of the crystalline lens with age. It can be corrected by use of the convex lens.
5. Cataract. The lens becomes opaque due to different reasons. It can be corrected by removing the lens and replacement by a convex lens by the specialist.
6. Glaucoma. It is an increase in intraocular tension when the pressure within the eye is raised above the normal level (15-20 mm Hg.) If prolonged it brings about blindness.
7. Trachoma. It is caused due to infection by virus conjunctivitis. The cornea may be ulcerated and vision is lost.
8. Squint/ Strabismus/Diplopia  – It is the formation of two images. Corrected surgically.

Evolution Neet Revision Notes

NEET Biology Sense The Ear

The ear consists of three parts :

1. External
2. Middle
3. Internal ear.

External Ear. The external or the outermost projecting part of the ear is a skin-covered cartilaginous organ called pinna. It collects sound waves and admits them into the tubular auditory passage.

• Some animals can move their external ears in the direction of sound, but such muscles are vestigial in man although some people do have the capacity to move their ears slightly. A waxy layer of cerumen glands in the auditory passage entangles the bacteria and any other minute organisms that may creep in.
• Similarly, the outer openings have fine hair for protection purposes. Somewhat obliquely placed at the inner end of the auditory passage is a delicate blue-grey membrane called the ear drum (tympanum).

Middle Ear. The middle ear consists of a set of three tiny bones, which are lodged in a chamber. The first bone is the hammer-shaped malleus, attached to the inner surface of the car drum (tympanum), by a muscle called tensor tympani.

• Next is the anvil-shaped incus and the third is the stirrup-shaped stapes, the inner end of which is attached to fenestra malls. An air passage of the castellan tube connects the floor of (the middle ear with the pharynx, to balance the air pressure on either side of the tympanum.
• The tympanic cavity opens into the internal ear’s cavity through two apertures – fenestra ovalis and fenestra rotundas.

The car ossicles help in the amplification of sound waves and their transmission to the internal car. These are three in mammals as a characteristic feature :

1. The malleus (hammer) comes first connected to the tympanum, derived from the articular bone of the low er jaw.
2. The incus (anvil) is the second bone upon which the malleus hammers. It is derived from the quadrate bone of the upper jaw.
3. Stapes (stirrup) the last, fork-shaped bone is connected to the membrane of fenestra ovalis. It is derived from oromandibular, a homologous bone, columella auris is the only ear ossicle found in frogs.
4. The middle car is connected with the pharynx through a cartilaginous eustachian tube which gets filled with air and helps maintain equal pressure on both sides of the tympanum.
5. The internal car is very delicate. It has two main regions – the upper utriculus and the lower sacculus. Both are connected by a small and narrow saccule-utricular duct. A small duct, the endolymphatic duct, opens into it; the other end of which opens into a closed endolymphatic sac which is present on the posterior side of the temporal bone.
6. The upper portion i.e. utriculus is connected with three semi-circular canals, which are concerned with the sense of position of the body and not with hearing.
7. From the sacculus arises a long tubular part or cochlea which is coiled like-conch shell and is embedded in a bone of the skull. It carries a system of canals and spaces which are filled with lymph-like fluid and there are fine sensitive membranes running across it.
8. Branches from the auditory nerve enter these membranes. This part is connected with the sense of hearing. The cochlea is attached to the sacculus through ductus reuniens. Cochlea has about 2 coils. The cochlea can be divided into three parts the upper one is scala vestibuli, the middle scala media and the lower one is scala tympani.
9. The upper and lower parts are filled with perilymph whereas the middle one with endolymph. Both the scala vestibule and scala tympani are continuous with each other through a passage called helicotrema.
10. The dorsal wall of scala media is called Reissner’s membrane and the ventral one is the Basilar membrane. Several sensitive structures are found on the basilar membrane like an organ of Corti, cell of deiter, the cells of Hensen and the tectorial membrane.

Evolution Neet Revision Notes

NEET Biology Sense Equilibrium

• Any alteration in body posture causes the otoliths within the endolymph of the cristae and maculae to contact sensory hairs, generating an impulse that is transmitted to the brain, which then adjusts to maintain balance.
• The cristae in the ampulla of semicircular canals sustain dynamic balance. It is activated when the body is in motion or rotation.
• The maculae in the utriculus and sacculus ensure static balance or orientation of the body or head during a static position (sitting or standing).

NEET Biology Sense Hearing

The process of hearing and its path of sound waves is as follows:

• Sound waves collected by pinna → external auditory meatus→ tympanum →tympanic cavity → ear ossicles (malleus→ incus → stapes) → membrane of fenestra ovalis → perilymph of scala vestibuli →helicotrema →scala tympani (vibrations cause movement of Reissner’s and basilar membranes result in the vibration of endolymph of scala media) → Tectorial membrane →Sensory hair cells of the organ of Corti → Impulse ’ generated → Auditory nerve→ Brain (perception and interpretation of sound vibrations) and sound Is perceived.

Evolution Neet Revision Notes

NEET Biology Sense Organs In Focus

1. Receptors are merely involved in receiving the stimuli and initiating the nerve impulses but cannot interpret the impulses.
2. Interpretation power of nerve impulses lies in the specific sensory areas of the brain,
3. Proprioceptors are maximally present in the sole of feet.
4. Exteroreceptois and proprioceptors are somatic receptors while interoceptors are visceral receptors,  Classification of receptors was given by Sherrington. Reading of a page is an example of exteroception i.e., sensing of the external environment, or Sensing of internal condition and position is inerorecspection.
5. Perception is the conscious awareness and interpretation of sensation.
6. Each eye weighs roughly 7 gins.
7. Photoreceptor cells are present on the innermost layer of the eye. the retina.
8.  The Iris of the eye contains radial bands and rings of circular smooth muscles.
9. The size of the pupil is larger in human females than in males. The Iris of the eye acts as a diaphragm of eye. Iris, being pigmented. gives colour to the eye which depends upon the amount of melanin present example, more melanin in brown eye, less melanin in blue eye but no melanin in albino eye.
10. Rods of the retina have rhodopsin (visual purple) while cones have iodopsin (visual violet), and Rods help in night vision. twilight and Black and white vision, while cones help in day vision and colour vision.
11. There are about 7 million cones in the human eye.
12. Zonula of Zinn is the other name for the suspensory ligament.
13. Monocular vision is found in animals like dogs, rabbits, pigeons, frogs, etc. In this, only one eye is focused on one object at a time.
14. Stereoscopic vision. Binocular vision is Found in most primates and owls among the birds. In this, both eyes can be focused on the same object at the same time.
15. In flatfishes, both eyes are on the right side of the body. Palpebrae. Eyelids. These act as shutters.
16. Meibomian glands are modified oil glands.
17. Glands lying at the edges of eyelids Gland of Zeis and Gland of Moll.
18. Sty Bacterial infection of the gland of Zeis. It is also called
19. hordeolum.
20. Eyelids are absent in cyclostomes, bony fishes and snakes.
21. Plica semilunaris. The third eyelid, also called the nictitating membrane, is vestigial in man.
22. The cornea is non-vascu, a part of the eye. So cornea is most easiest part to transplant as n does not stimulate the immune system.
23. Nutrition to the cornea is provided by alkaline lacrymal secretion. It is differentiated into Bulbar conjunctiva (outside cornea) and palpebral conjunctiva (inner to eyelids). It is a modified stratified epithelium.
24. Owls have a large number of rods and only a few cones in the retina of their eyes.
25. The retina of the fowl’s eye contains only cones.
26. Deer have the biggest eyes in proportion to body size.
27. The region of the environment from which each eye collects light is called the visual field.
28. The normal eye can accommodate light from objects from about 25 cm to infinity.
29. In the ear canal, there are about 4.000 specialized ceruminous glands.
30. The cochlea contains 16.000 and 24.000 hair cells and each hair cell has about 100 hair. They create waves in the lymph fluid of the cochlea and the wave causes the basilar membrane to ripple.
31. The ear acts as a statoacoustic organ that controls hearing and equilibrium.
32. The Pinna of the ear is called the auricle.
33. The pharyngeal opening of the eustachian tube opens during yawning, swallowing and during the ascent or descent of an aeroplane to equalise the pressure inside the tympanic cavity to that outside the eardrum for free vibrations of the eardrum.
34. Audiology. Study of hearing power.
35. Otology. Study of the structure, working and disorders of the ear.
36. Aquatic animals like seals, whales, etc. and monotremes like duck-billed platypi and spiny ant-eaters lack pinna.
37. Thermoreceptors are more in number on the face and hand of man.
38. The most sensitive chemical receptors are the taste and smell receptors.
39. Taste receptors in the tongue respond specifically to sweet, sour, salty and bitter molecules.
40. The nose contains mucus-coated olfactory receptors, over 2 million in number.
41. The mucus produced by Bowman’s gland absorbs odour-iferous substances that stimulate the reception of the cells.
42. The taste of chillies, black pepper and ‘hot’ sauces is not a true sensation. It is a sensation of burning pain produced by the stimulation of pain receptors of the tongue.
43. Many insects such as honey bees, flies, butterflies and moths possess chemoreceptors to taste sensation on their feet.
44. Some mammals such as rhesus monkeys, pigs, cats and dogs possess taste buds for tasting water. But man is deprived of them.

Evolution Neet Chapter Summary

NEET Biology Sense Organs Conclusion

• In fishes, accommodation for near objects is brought about by elongating the eyeball but in other animals, it is brought about by increasing the lens curvature.
• lives, capable of focussing the images of objects possessed by vertebrates and some higher invertebrates like prawns, crabs and insects.
• Prawns, crabs and cockroaches possess compound eyes, each made of many elongated tube-like units called ommatidia. They are crowded over a spherical surface and produce a composite blurred image of the object.
• All animals do not have their olfactory receptors located in the nose. For instance, moths and butterflies possess olfactory chemoreceptors on their antennae.
• The cornea has no vascular or immune systems. Therefore a complete transplant is not rejected by the body and is highly successful.
• Cornea from the eye of a dead person can be stored and transplanted to restore vision in another person. It is so because it is non-vascular and does not stimulate the immune system.
• Owls have the keenest eyesight at night because their eyes have a large number of rods and a few cones in the retina.
• Aquatic mammals like seals, whales, etc., and monotremes like duck-billed platypus and spiny ant eater lack pinna. Tympanum. It is the specialized hearing organ of insects.
• Sea sickness. Tendency of nausea and vomiting due to unusual stimulation of semicircular ducts by the movement
  ment of a ship in the sea.
• The area of the body most sensitive to the sensation of cold is the chest Merkel’s disc is slowly adapting receptors for touch.
• Organ of Ruffini arc the receptors for warmth.
• Cynnolabs. Cone cells are sensitive to blue light radiations.
• Erythrolabs. Cone cells are sensitive to red light radiations.
• Jacobson’s organs. Additional smelling organs of reptiles like Sphenodon, lizards and snakes (best developed). These are also called vomeronasal organs.
• Ampullae of Lorenzini. Thermoreceptors are found in the snout region of fishes.
• A sense of direction is given by the nose.
• Olfactory cells are modified bipolar neurons.
• Grandy’s corpuscles. A special type of Merkel’s corpuscles present in the skin and tongue of birds
• Otoliths/Otoconia. Calcium carbonate crystals
• Harberf s corpuscles. A simple type of Pacinian corpuscles in birds
• Pacinian corpuscles. Vater’s corpuscles and hence Vater Pacinian corpuscles
• Vibration to which the human ear is most sensitive. 1000 cycles /sec
• Harderian glands -Present at an angle of the eye, secrete lubricant for nictitating membrane.
• Eyelids are absent in snakes.

NEET Biology Sense Organ Multiple Choice Questions

Question 1. The Human Retina Can Detect Three Basic Colours. Select The Correct Set Of Colours :

1. Blue, Red And Orange
2. Blue, Red And Yellow
3. Blue, Red And Green
4. Blue, Green And Yellow.

Answer: 3. Blue, Red And Green

Question 2. The Charts Helping To Identify If A Person Is Colour Blind Are :

1. Ishihara’S Charts
2. Reprogram
3. Dichromatic Charts
4. Accommodation Charts.

Answer: 1. Ishihara’s Charts

Question 3. In the Human Eye Maximum Refraction Of Light Takes Place In the:

1. Cornea
2. Aqueous Humour
3. Lens
4. Vitreous Humour.

Answer: 1. Cornea

Read and Learn More NEET Biology Multiple Choice Question and Answers

Sensory Organs MCQ Objective Question Question 4. Which Part Of The Ear Is Common To Both Frogs And Mammalian Ear?

1. Cochlea
2. Eustachian Tube
3. Organ Of Corti
4. Columella Auris.

Answer: 2. Eustachian Tube

Question 5. Algesireceptors Are Sensitive To :

1. Pressure
2. Coldness
3. Chemicals
4. Pain.

Answer: 4. Pain.

Question 6. How Many Semicircular Canals Are Present In The Ear Of Frog And Man?

1. 3, 2
2. 3, 3
3. 3,1
4. 1, 3.

Answer: 2. 3, 3

Question 7. Colliculi In Eutherians :

1. Are Bigger Than Those In Frog
2. Are Two In Number
3. Concerned With Vision And Audition
4. Concerned With Vision And Maintenance Of Equilibrium.

Answer: 3. Concerned With Vision And Audition

Question 8. The Ends Of Bipolar Neurons In Retina Of Man Touch :

1. Choroid Layer And Ganglion Cells
2. Photosensitive Cells And Ganglion Cells
3. Cornea And Retina
4. Blind Spot And Yellow Spot.

Answer: 2. Photosensitive Cells And Ganglion Cells

Question 9. What Will Happen If The Eyes Of A Frog Are Covered With Paper?

1. Frog Will Not Move
2. Frog Will Die Soon
3. Frog Will Move To One Side Only
4. Frog Will Not Do Anything.

Answer: 4. Frog Will Not Do Anything.

Question 10. Which Of These Has the Biggest Eyes In Proportion To Body Size?

1. Horse
2. Camel
3. Elephant
4. Deer.

Answer: 4. Deer

Sensory Organs MCQ Objective Question Question 11. The Outer Coat Of Eye Ball Is Known As :

1. Sclerotic
2. Choroid
3. Retina
4. Vascular Ciliary Layer.

Answer: 1. Sclerotic

Question 12. The Middle Coat Of The Eye Ball Is Vascular And Made Up Of:

1. Smooth Muscles
2. Epithelial Cells
3. Circular Muscles
4. Connective Tissue And Black Pigments.

Answer: 4. Connective Tissue And Black Pigments.

Question 13. Iris Is Made Up Of:

1. Rods And Cones
2. Circular And Radial Muscles
3. Glandular Epithelium
4. Adipose Tissue.

Answer: 2. Circular And Radial Muscles

Question 14. The Rods Of Retina Are Most Closely Associated With :

1. Blind Spot
2. Colour Vision
3. Bright Light Vision
4. Feeble Light Vision.

Answer: 4. Feeble Light Vision.

Question 15. Rods And Cones In Retina Of Vertebrates Eye Differ In Their Function. Indicate The False Statement:

1. Rods Can Be Stimulated By Low Intensity Of Light While Cones Require High Light Intensity For Stimulation
2. Rods Give A Blurred Image Of An Object While Cones Give Its Sharp Visual Details
3. Rods Give Colour Vision While Cones Give Black And White Perception
4. Both 1 And 3.

Answer: 3. Rods Give Colour Vision While Cones Give Black And White Perception

NEET Biology Sense Organ Question 16. Cavity Of Vitreous Chamber Is :

1. Behind The Lens
2. In Front Of Lens
3. Between Choroid And Retina
4. Between Sclerotic And Choroid.

Answer: 1. Behind The Lens

Question 17. Long Eye Ball Relation To Its Refracting Power Is :

1. Long Sight
2. Myopia
3. Astigmatism
4. Hypermetropia.

Answer: 2. Myopia

Question 18. Visual Purple Is Pigment Concerned With :

1. Colour Of Eye
2. Night Blindness
3. Colour Blindness
4. Perception Of Image In Darkness.

Answer: 4. Perception Of Image In Darkness.

Question 19. Rhodopsin Of Eye Will Require :

1. Mango
2. Carrot
3. Wheat
4. Banana.

Answer: 2. Carrot

NEET Biology Sense Organ Question 20. Iodopsin Is Associated With :

1. Hypophysis
2. Cones
3. Goitre
4. Cretinism.

Answer: 2. Cones

Question 21. The Vitreous Humour Differs From The Aqueous Humour In:

1. Being Much More Watery
2. Having A Less Refractive Index
3. Being More Viscous
4. Being More Translucent.

Answer: 3. Being More Viscous

Question 22. The Retina Of Vertebrate Eye Consists Of :

1. Rods Only
2. Cones Only
3. Rods And Cones And Neuroglial Cells
4. Rods And Cones.

Answer: 3. Rods And Cones And Neuroglial Cells

Question 23. In Annual Vision Photochemical Sensitivity Of:

1. Carotene Is Used
2. Keratin Is Used
3. Atp Is Used
4. Cuticle Is Used.

Answer: 1. Carotene Is Used

Question 24. Aperture Controlling Light Passage In the Eye Is :

1. Sclerotic
2. Pupil
3. Blind Spot
4. Iris.

Answer: 2. Pupil

NEET Biology Sense Organ Question 25. The Shape Of Lens In The Eye Of Vertebrate Is Altered By :

1. Iris
2. Vitreous Humour
3. Aqueous Humour
4. Ciliary Muscles.

Answer: 4. Ciliary Muscles.

Question 26. Fovea Centralis In The Human Eye Is Having :

1. Mixture Of Rods And Cones
2. Rods Only
3. Cones Only
4. Nerve Endings Only.

Answer: 3. Cones Only

Question 27. In Vision Light Energy Is :

1. Converted Into Chemical Energy
2. Converted Into Electrical Energy
3. Converted Into Mechanical Energy
4. Converted Into Physical Energy.

Answer: 1. Converted Into Chemical Energy

Question 28. Tapetum Lucidum Layer Is :

1. Jelly-Like
2. Fibrous
3. Crystalline Fibrous
4. Crystalline.

Answer: 4. Crystalline

Questions for NEET Biology Sense Organ Question 29. After Exposure To Bright Light, Some Time Is Needed For Dark Adaptation Because :

1. Rhodopsin Becomes Temporarily Degenerated
2. Rhodopsin Is Bleached By Light And Requires Some Time For Normal Position
3. Rhodopsin Changes To Post-Rhodopsin In Dim Light And This Takes Some Time
4. None Of The Above.

Answer: 1. Rhodopsin Becomes Temporarily Degenerated

Question 30. In Frog’s Eye Sclerotic Is Made Up Of:

1. Bone
2. Muscle And Cartilage
3. Cartilage
4. Fibrous Connective Tissue.

Answer: 4. Fibrous Connective Tissue.

Question 31. The Part Of An Eye Which Acts Like A Diaphragm Of Photographic Camera Is :

1. Pupil
2. Iris
3. Cornea
4. Lens.

Answer: 2. Iris

Question 32. The Wall Of The Eye Is Made Up Of:

1. Four Main Layers
2. Three Main Layers
3. Thirty Main Layers
4. One Layer Only.

Answer: 2. Three Main Layers

Question 33. Focus In The Vertebrate Eye Is Done By :

1. Iris Muscles
2. Ciliary Muscles
3. Muscles Of Eye Ball
4. Retinal Muscles.

Answer: 2. Ciliary Muscles

Questions for NEET Biology Sense Organ Question 34. Tapetum Lucidum  Present :

1. In Retina
2. Cither In Retina Or Clitrfoid
3. In Choroid
4. None Of The Above.

Answer: 2. Cither In Retina Or Clitrfoid

Question 35. Myopia Occurs When The Image or Distant Object Is Focussed :

1. Behind The Retina
2. Above The Retina
3. In Front Of The Retina
4. Below The Retina.

Answer: 3. In Front Of The Retina

Question 36. Astigmatism Is Due To The Irregularities :

1. In The Shape Of Lens And Cornea
2. Of Pigments
3. Of Rods
4. Of Lens.

Answer: 1. In The Shape Of Lens And Cornea

Questions for NEET Biology Sense Organ Question 37. Hypermetropia Occurs When The Image Of Near Objects Is Focussed :

1. Above The Retina
2. Upon The Retina
3. Below The Retina
4. Behind The Retina.

Answer: 4. Behind The Retina.

Question 38. Presbyopia Is Due To The Irregularities :

1. In The Shape Of Lens And Cornea
2. In The Shape Of Lens And Loss Of Its Elasticity
3. In The Shape Of Cornea
4. In The Shape Of Iris.

Answer: 2. In The Shape Of Lens And Loss Of Its Elasticity

Question 39. Night Blindness Is Caused Due To’ The Deficiency Of:

1. Vitamin A
2. Vitamin B
3. Vitamin K
4. Vitamin D.

Answer: 1. Vitamin A

Question 40. Fenestra Vestibuli Amplifies Sound Vibrations By :

1. 2.2 Times
2. 4.5 Times
3. 10 Times
4. 20 Times.

Answer: 1. 2.2 Times

Question 41. Hypoglossal Nerve Is Responsible For The Movement Of Muscles Of:

1. Tongue
2. Ear
3. Eyes
4. Nose

Answer: 1. Tongue

Question 42. Skin Receptors Are Classified Into How Many Categories?

1. Two
2. Five
3. Four
4. Six

Answer: 1. Two

Question 43. The Iris Consists Of Delicate :

1. Ciliary Muscles
2. Roilgh Muscles
3. Soft Muscles
4. Muscles Without Cilia.

Answer: 1. Ciliary Muscles

Sensory Organs MCQ Objective Question Question 44. Short-Sightedness Occurs When The Image Of A Distant Object Is Focussed :

1. On The Back Of The Retina
2. Above The Retina
3. In Front Of The Retina
4. Below The Retina.

Answer: 3. In Front Of The Retina

Question 45. The Function Of Iris Is To :

1. Alter The Size Of Pupil
2. Move The Lens
3. Close The Eyelids
4. Secrete Aqueous Humour.

Answer: 1. Alter The Size Of Pupil

Question 46. Colour Blindness Is :

1. Sex-Linked Genetic Disorder
2. Defect In Lens
3. A Gene Mutation
4. Chromosomal Mutation.

Answer: 1. Sex-Linked Genetic Disorder

Question 47. Colour Blindness Is The Inability To Distinguish Colour Between :

1. Red And Green
2. Red And Yellow
3. Blue And Black
4. Green And Blue.

Answer: 1. Red And Green

Question 48. The Region Of Clearest Vision In Reina Is Yellow Spot Which Is Known As ;

1. Fovea Vvntiabs
2. Canails Cenlialis
3. Macula Lutea
4. Corpus Luteum.

Answer: 3. Macula Lutea

Sensory Organs MCQ Objective Question  Question 49. Stereoscopic Vision Is Found In :

1. Fish
2. Frog
3. Man
4. Snake.

Answer: 3. Man

Question 50. The Hammer Like Ear Ossicle Is:

1. Malleus
2. Incus
3. Stapes
4. Cochlea.

Answer: 1. Malleus

Question 51. Hat Drum Is Not Responsive To Changes Of:

1. Volume Of Sound
2. Position Of The Body
3. Frequency Of Sound Waves
4. Air Pressure In The Pharynx.

Answer: 2. Position Of The Body

Question 52. Semicircular Canals In Internal Ear Are Concerned With :

1. Balance Of The Body
2. Hearing
3. Intelligence
4. Balance And Hearing.

Answer: 4. Balance And Hearing.

Question 53. Which Of These Is Not An Ossicle Of the Middle Ear Of a Frog?

1. Malleus
2. Columella
3. Stapes
4. None Of These.

Answer: 1. Malleus

Question 54. Eustachian Tube In Case Of Man Connects Ear With :

1. Pharynx
2. Oesophagus
3. Bucco-Pharyngeal Cavity
4. Salivary Duct.

Answer: 1. Pharynx

Question 55. The Sound Reaches The Inner Ear From Ear Drum Through Structures Which Are In A Definite Series. The Series Is :

1. Malleus-Incus-Stapes
2. Columella-Stapes
3. Stapes-Malleus-Incus
4. Malleus-Stapes-Incus.

Answer: 1. Malleus-Incus-Stapes

Question 56. The Internal Ear Of Vertebrates Is Filled With A Fluid Called :

1. Endolymph
2. Perilymph
3. Haemolymph
4. Lymph.

Answer: 1. Endolymph

Question 57. The Site From Which The Nerve Impulse For Hearing Originates Is :

1. Ear Ossicle
2. Cochlea
3. Tympanum
4. Auditory Nerve.

Answer: 2. Cochlea

Sensory Organs MCQ Objective Question  Question 58. Lateral Line System Helps In :

1. Detecting Water Current
2. Echolocation
3. Thermoregulation
4. All Of The Above.

Answer: 1. Detecting Water Current

Question 59. Otolith Is Formed Of:

1. Calcium Carbonate
2. Calcium Oxalate
3. Magnesium Carbonate
4. Magnesium Sulphate.

Answer: 1. Calcium Carbonate

Question 60. Sensory Patch Of Ampulla Is Called :

1. Cristae
2. Maculae
3. Otoliths
4. Basilar Papilla

Answer: 1. Cristae

NEET Biology Evolution Of Man

Male Primula is positioned to inquire about his origin.

• Male Is classified within the order Primates alongside monkeys and apes.
• The ancestors of humans and other comparable species developed approximately 24 million years ago.

NEET Biology Evolution Of Man Relationship Of Man With Other Primates

The older primate includes three sub-orders. Leinuroidac, Tarsioidac, and Anthropoidae. The Leminoidne and Tarsioidac are collectively called prosimians and Anthropoidae are called simians.

Read and Learn More NEET Biology Notes

• The first mammal was 210 million years old, the first primate 80 million years, the first anthropoid apes 36 million years, and the first hominids 24 million years ago.
• The three families of modern hominids are the Hominidae (the family of man), llylobatidae (Gibbous), and the Pongidne (chimpanzees, gorillas, and orangutans).
• The unique features of the man are erect posture, shorter arms, and a large brain, and can fabricate special tools, use spoken language, and practice prolonged parental care.

• The evolutionary history of man has been built up from the study of fossils and molecular homology.
• Human evolution took place in Africa and Asia.
• A common ancestry for great apes and man has been deduced from similarities in DNA contents, chromosome number, and banding pattern.

Human Evolution NEET Notes

NEET Biology Evolution Of Man Human Evolution

The evolution of man is associated with intelligence and bipedal locomotion

• TA. Huxley (1863)– Book ‘Man’s Place in Nature’ Charle’s Darwin (1971) – ‘Descent of Man’.
• Darwin suggested Man, Apes, and monkeys had a common ancestor.
• Mammals evolved in the early Jurassic period about 210 million years ago from Cynodont Reptiles.

Cotylosaurs → Cynodont → Mammals (Stem reptiles) (reptiles)

Early History

1. Dryopithecus (Proconsul, 18-24 million years)—Common ancestor of humans and apes that lived in Asia as well as Africa. Common species D. africanus. Semi-erect, with hind limbs and forelimbs of the same size.
2. Ramapithecus (Kenyapithecus, 8-15 million years)—It was the earliest man like Primate which probably walked on its legs and possessed dentition similar to humans.
3. Australopithecus (Southern ape, First ape-man, 2-5 million years)—A. africanus was lightly built and omnivorous while weight was 20-30 kg.
   • A. robustus was heavily built and vegetarian, height-120 cm, Cranial capacity-380-430 cm.
   • Face-Prognathous (Projecting Type)—Low forehead, prominent brow ridges, no chin, bipedal locomotion but with bent knees, used crude tools.
4. Homo Habilis (2 Million Years)—Bipedal Locomotion with 150 cm height, (40-50 kg) Cranial capacity 680 cm3, Prominent brow ridges and hominid teeth. He was the first toolmaker. Used chipped stone tools.
5. Homo erects (1.7 Million Years, Erect man)—It walked on erect long legs, 150 cm, cranial capacity 775-1225 cm³, prominent brow ridges, no chin, massive jaws, and longer teeth. Semi-erect posture made more elaborate tools, hunted big game birds, used lire, and primitive speech.
6. Java man (Homo Crectus Credits)—had a smaller cranial capacity (775-900 cm³)— first used fire for cooking and protection.
7. Peking Man (Homo Erectus Pekinesis)—(H. eredus Sinanthropus) had sharp and chisel-shaped tools. Large cranial capacity (915-1225 cm³) Neanderthal Man (Homo sapiens neanderthalcnsis)-30,000-50,000 years ago. 150 cm, Cranial capacity (1300-1600 cm³), sloping forehead, brow ridges, chin, and thick bones of the skull which protruded behind strong shoulders and arms, used tools, and animal hides. Lived in caves and probably built hut-like shelters-had religious feelings and burial customs.
8. Cro-Magnon Man (H. sapiens Fossilis) 20,000-50,000 years back, 180 cm, Cranial capacity-1600 cm³, Broad forehead but arched, brow ridges moderate, strong jaws with man-like dentition, and a well-developed chin. The face was perfectly orthognathous with an arrow and elevated nose. Cave dwellers, the hunter with the domesticated dog, used stone spears and arrowheads, paintings, etc.
9. Modern Man (H. sapiens Sapiens): evolved about 25,000 years ago and spread only about 10,000-11,000 years ago. Cranial capacity- (1400-1450 cm³). Four flexes in the vertebral column, a slight raising of the skull cap.

Time Scale Related To Human Evolution

NEET Biology Evolution Of Man Evolutionary Changes During Human Evolution

1. Skull And Brain. Increase in size, complexity, and intelligence.
2. Bipedal Locomotion. Due to bipedal locomotion forelimbs became free.
3. Forelimbs. Modified into organs of manipulation and lengthening of hindlimbs and shortening of forelimbs.
4. Thumb. Perfection of thumb opposability in forelimbs.
5. Toe. Loss of opposability of great toe in hind limbs.
6. Upright posture. Erect posture by the development of lumbar curve.
7. Jaw. Jaw power reduced.
8. Teeth. Due to omnivorous feed habits, the size of incisors and canines is reduced.
9. Chin. Development of chin.
10. Pelvic Girdle. Development and broadening of iliac bones of the pelvic girdle.
11. Social organization and cultural evolution.

NEET Biology Human Evolution Notes Pdf

Evolution Of Man

Early Human Evolution

NEET Biology Evolution Of Man Synopsis

Evolutionary History Of Man

1. The evolution of hominids occurred in Africa and Asia.
2. The evolution of man took place in Africa.
3. Dnvpiihecus and Ramapithccus lived about 15 million years ago; they were hairy and walked like apes.
4. 3-4 million years before man-like primates walked in Eastern Africa; they were about 4 feet tall and walked upright.
5. Rcmuipithecus and Sivapithecus lived in Africa and Asia and were the forerunners of hominids.
6. Genus Australopithecus appeared in Africa about 5 million years ago.
7. The genus Homo appeared about 2 million years ago.
8. Homo habilis lived in Africa about 2 million years ago and was characterized by a larger brain; could use tools.
9. Homo credits appeared about 1.7 million years ago and believed to have migrated to Asia and Europe.
10. As a result of the abrupt transition that occurred in Europe about 84000 years ago, Neanderthal man was wiped out and gave way to more efficient Cro-Magnon.
11. Homo sapiens evolved about 10000 years ago.

• Leaky (1930) excavated the first fossil ape Proconsul from early Miocene rocks around Lake Victoria of Kenya. It had 5 cusped molars.
• Leaky (1959) excavated fossils of Zijanthropus (15.5 lakhs year old rocks).
• Leaky (1960) excavated fossils of Homo habilis. (16 to 18 lakhs yrs old).
• Dryopithecus. This fossil ape is known from middle Miocene or early Pliocene rocks
• Sivapithecus was excavated from the middle and late Pliocene rocks of the Shivalik hills of India.
• Fossils Of Ramapithecus And Kenyapithccus were excavated by Lewis (1930) and Leaky (1955) from about 1.2 to 1.4 crore-year-old rocks from Kenya, China, and India.
• Raymond Dart 1924 excavated a fossil baby skull (Tuang baby) from the Pliocene rocks of Australopithecus near Tuang in Africa.
• Robert Brown (1936 onward) excavated fossils of Paranthropus (10-18 yrs old, Pleistocene rocks of Africa).

The most primitive and earliest ape during the Oligocene is called Parapithccus.

• Linnaeus was the first scientist who placed human beings along with monkeys and apes.
• The skull of Pithecanthropus was found in Java.
• Geological evidence for the most primitive numerals found in C. Africa.
• Apes are characterized by the absence of a tail.
• The most primitive ape is Gibbon while the most advanced is Gorilla.
• Old-world Monkeys (Ceboids). Long prehensile (grasping) tails and flat noses, ground dwellers example, Baboons, Rhesus monkeys

New World Monkeys (Ccrcopithecoids) have No such tails but have protruding noses example, spider monkeys, organ grinder’s monkeys (capuchin)

• The first evidence of Australopithecus was the skull of a child discovered by Raymond Dart. Later in 1974 a complete skeleton named Lucy was found by Donald Johanson and Timothy white
• Mitochondrial Eve—A member of archaic Homo sapiens
• The Efe pygmies of Zaicr’s Itwi Forest are among the world’s shortest people, with males reaching an average of 4. 8″ (1,42m) and females reaching 4′ 5″ (1.35 m)
• Piltdown man. It is hypothetical and developed on the basis of artifacts consisting of fragments of skull at Piltdown England

NEET Biology Chapter Evolution Of Humans

Cultural Evolution Is Divided Into Three Phases:

Paleolithic Era. The evolution of knowledge regarding rudimentary hunting implements and primitive language: the human species was Homo habilis.

• Mesolithic Period. Development of intricately designed implements for collective hunting, pyrotechnology, animal skin processing, lithic artistry, and ivory craftsmanship.
• The primary human kinds were Neanderthals and Cro-Magnons.
• Neolithic Period. Progressive development of agriculture, animal domestication, matrimonial practices, education, science, and technology.
• The Indian subcontinent and the Middle East are the initial locations of agriculture. This phase encompassed Homo sapiens.

Percents Of Bands Common Among Humans 

• Chimpanzees: 99 %
• Gorillas: 99%
• Orangutans: 99%
• African Green Monkeys: 95%
• Domestic Cats: 35%
• Mice: 7%

Cranial Capacities

• Chimpanzee (Ape): 400 cc
• Gorilla (Gorilla): 650 cc
• Australopithecus: 300-500 cc
• Java ape Man (Pithecanthropus): 800-1000 cc
• Peking Man (Sinanthropus): 1075 cc
• Neanderthal Man: 1400 cc
• Rhodesian Man: 1280 cc
• Cromagnon Man: 1600 cc
• Modern Man (Homo sapiens): 1900-1450 cc

NEET Biology Evolution Of Man Multiple Choice Questions And Answers

Question 1. First Homonids are:

1. Ramapithecus
2. Kcnyapithccus
3. Both 1 and 2
4. Australopithecus.

Answer: 3. Both 1 and 2

Question 2. Who was the first civilized man?

1. Cro-Magnon min
2. Neanderthal man
3. Hcidelbcrgs man
4. Temifier man.

Answer: 2. Neanderthal man

Question 3. The first human fossil probably belonged to:

1. Zizanthropus
2. Australopithecus
3. Pleisanthropus
4. Pilhicanthropus.

Answer: 2. Australopithecus

Read and Learn More NEET Biology Multiple Choice Question and Answers

Evolution NEET Practice Questions MCQs Question 4. The age of mammals is known as:

1. Cenozoic
2. Mesozoic
3. Palaeozoic
4. Psychozoic.

Answer: 1. Coenozoic

Question 5. The direct ancestral race of modern man was possibly:

1. Cromagnon man
2. Peking man
3. Neanderthal man
4. Java man.

Answer: 1. Cromagnon man

Question 6. Which of the following is not in the direction of the evolution of the human species?

1. Raised orbital ridges
2. Binocular vision
3. Opposable thumb
4. Developed brain.

Answer: 1. Raised orbital ridges

Question 7. Which one of the following eras in the geological time scale corresponds to the Person when life has not originated upon earth?

1. Palaeozoic
2. Mesozoic
3. Cenozoic
4. Azoic.

Answer: 4. Azoic

Question 8. Among the primates listed below which one is the closest relative of modern man:

1. Gorilla
2. Sinanthropus
3. Gibbon
4. Orangutan.

Answer: 2. Sinanthropus

Question 9. The Java man is considered to have existed in:

1. Java only
2. China only
3. Africa
4. Java, China, and Africa.

Answer: 4. Java, China, and Africa.

Evolution NEET Practice Questions MCQs Question 10. Neanderthal man:

1. Resembles modem man
2. Was less advanced than modern man
3. Had a larger brain than modern man
4. Had a much smaller brain than modern man.

Answer: 3. Had a larger brain than modern man

Question 11. The ancestor of the man who first stood erect was:

1. Java man
2. Australopithecus
3. Peking man
4. Cro-magnon.

Answer: 2. Australopithecus

Question 12. Which of (lie following is true for Homo sapiens?

1. Protruded mouth
2. Cranial capacity 1450 cc
3. Canine absent
4. Jail present.

Answer: 2. Cranial capacity 1450 cc

Question 13. The skull of Pithecanthropus erectus was found in:

1. Africa
2. Java
3. America
4. All of the above.

Answer: 2. Java

Question 14. The pre-historic ancestor of man which existed during the Pleistocene era is:

1. Australopithecus
2. Zinjanthropus
3. Neanderthal man
4. Atlantic man.

Answer: 3. Neanderthal man

Question 15. The most recent fossil is of:

1. Cromagnon man
2. Java man
3. African man
4. Peking man.

Answer: 1. Cromagnon man

Evolution NEET Practice Questions MCQs Question 16. The name of the fossil man of Shivalik Hills is:

1. Australopithecus
2. Dryopithecus
3. Sivapithecus
4. Ramapithecus.

Answer: 4. Ramapithecus.

Question 17. The recent ancestors of modern man were:

1. Java ape man and Peking man
2. Peking and Rhodesian man
3. Rhodesian man and Cromagnon man
4. Cromagnon man and Neanderthal man.

Answer: 4. Cromagnon man and Neanderthal man

Question 18. Homo erectus is the zoological name of:

1. Java ape man
2. Peking man
3. Neanderthal man
4. Nutcracker man.

Answer: 1. Java ape man

Question 19. The earliest site where human civilization and crop cultivation started was presumably:

1. Around the Caspian and Mediterranean Sea
2. Around river Nile
3. Chinese river Nile
4. All of the above.

Answer: 1. Around the Caspian and Mediterranean Sea

Question 20. Cromagnon man was:

1. Herbivorous
2. Frugivorous
3. Sanguivorous
4. Carnivorous.

Answer: 4. Carnivorous.

Biology MCQ Origin and Evolution of Man Question 21. Which one of the fossil men stood first?

1. Australopithecus
2. Homo erectus
3. Sinanthropus
4. Gigantopithccus.

Answer: 1. Australopithecus

Question 22. Neanderthal man differs from modern man in the:

1. Receding jaw
2. Protruding jaw
3. Can make good tools
4. Having a stockier body.

Answer: 4. Having a stockier body.

Question 23. Which of these is considered a trend in primate evolution?

1. Development of non-prehensile tail
2. Development of monocular vision
3. Decreased dependence on smell
4. Elimination of clavicle.

Answer: 3. Decreased dependence on smell

Question 24. Which primate existed in the first half of the Eocene epoch (53-58 million years ago)?

1. Prosinnans
2. Prosimians and monkeys
3. Prosimians, monkeys, and apes
4. Prosimians, monkeys, apes and hominids.

Answer: 1. Prosinnans

Question 25. Which of these prosimians are now found only on the island of Madagascar?

1. Lxuinir
2. Loris
3. Galago
4. Bush baby.

Answer: 1. Lxuinir

Biology MCQ Origin and Evolution of Man Question 26. The immortality of soul hypothesis has given rise to the discovery of:

1. Heidelbergensis man
2. Temifier man
3. Ncanderthalensix
4. Homo sapiens.

Answer: 3. Ncanderthalensix

Question 27. The present age is known as:

1. Bronze age
2. Iron age
3. Silver age
4. Golden age.

Answer: 2. Iron age

Question 28. Who discovered the use of the weapon and tools first?

1. Homo hails
2. Handyman
3. Both 1 and 2
4. Homo erectus

Answer: 3. Both 1 and 2

Question 29. Cannibalism is local in:

1. Java man
2. Peking man
3. Cromagnon man
4. Both (1) and (2).

Answer: 4. Both (1) and (2).

Question 30. The cranial capacity of Java ape-man was about:

1. 560 cc
2. 900 cc
3. 1300 cc
4. 1600 cc.

Answer: 2. 900 cc

Biology MCQ Origin and Evolution of Man Question 31. The first fossil of an African ape-man was discovered by:

1. Dr. Leaky
2. E.Dubois
3. Artlicr Keith
4. Raymond Dart.

Answer: 4. Raymond Dart.

Question 32. Peking man is known as:

1. Australopithecus
2. Sinanthropus
3. Pithecanthropus
4. Homo sapiens.

Answer: 2. Sinanthropus

Question 33. Which of the fossil men given below was an expert in making tools, weapons, paintings, etc?

1. Java ape-man
2. Peking man
3. African man
4. Cro-magnon man

Answer: 4. Cro-magnon man

Question 34. The cranial capacity was the largest in one of the following fossils of man:

1. Java ape-man
2. Cromagnon man
3. Neanderthal man
4. Peking man.

Answer: 2. Cromagnon man

Question 35. Continents where most of the primitive men have been discovered:

1. Africa
2. Asia
3. America
4. Australia.

Answer: 1. Africa

Question 36. Which of the following factors is considered best in the evolution of man?

1. Extinction of Reptiles
2. Appearance of Angiospenns
3. Preference for cave life
4. Pleistocene climate.

Answer: 4. Pleistocene climate.

NEET Biology Evolution Of Life MCQ Question Bank Question 37. Pithecanthropus erectus fossil was found in:

1. China
2. Japan
3. Java
4. Texas.

Answer: 3. Java

Question 38. The cranial capacity is nearly 1000 cc of:

1. Java man
2. Neanderthal man
3. Peking man
4. Cromagnon man.

Answer: 1. Java man

Question 39. The man who used stones for the first time was:

1. Cromagnon
2. Neanderthal man
3. Homo erectus
4. Homo habilis.

Answer: 4. Homo habilis.

Question 40. Which of the following is not a characteristic of apes?

1. Movement in the trees by brachiation
2. Movement on the ground by knuckle-walking
3. A wrist that bends backward
4. Highly mobile shoulder joints.

Answer: 3. Wrist that bends backward

NEET Biology Evolution Of Life MCQ Question Bank Question 41. Which of the following is not an anatomical change from ape to Homo sapiens?

1. From locking to non-locking knee joints
2. From a long, thin pelvis to a bowl-like pelvis
3. From opposable thumb to non-opposable thumb
4. From flat to arched feet.

Answer: 1. From locking to non-locking knee joints

Question 42. Tuang Baby is the name of:

1. Australopithecus
2. A. Africanus
3. A. afarensis
4. A. bosei.

Answer: 2. A. Africanus

Question 43. Early True Man was:

1. Peking Man
2. Java Man
3. Neanderthal Man
4. Homo habilis.

Answer: 4. Homo habilis.

Question 44. The dog was domesticated by:

1. Homo sapiens neanderthalensis
2. Homo sapiens fossilis
3. Homo heidelbergensis
4. Homo sapiens sapiens.

Answer: 3. Homo heidelbergensis

Question 45. The name of Mio-Pliocene apes is:

1. Dryopithecus
2. Paranthropus
3. Australopithecus
4. Ramapithecus.

Answer: 1. Dryopithecus

NEET Biology Evolution Of Life MCQ Question Bank Question 46. The maximum size of a modem brain is:

1. 2000 cc
2. 100 cc
3. 1500 cc
4. 2200 cc.

Answer: 3. 1500 cc

Question 47. The name of the earliest human ancestor from India is:

1. Paranthoropus
2. Ramapithecus
3. Australopithecus
4. Dryopithecus.

Answer: 2. Ramapithecus

Question 48. The latest ancestral race of modern man was possibly:

1. Java man
2. Peking man
3. Neanderthal man
4. Cromagnon man.

Answer: 4. Cromagnon man.

Question 49. “Peking Man” was:

1. Australopithecus
2. Sinanthropus
3. Zinjanthropus
4. None of the above.

Answer: 2. Sinanthropus

Question 50. Which of the following is not correct?

1. About 15 mya, primates called Dryopithecus and Ramapithecus appeared.
2. Homo erectus had a large brain around 900 cm³.
3. The brain capacities were between 650 to 800 cm³ of Homo habilis.
4. Ramapithecus was more ape-like.

Answer: 4. Ramapithecus was more ape-like

Question 51. Dryopithecus was:

1. Early human
2. Human ancestor
3. Ape ancestor
4. Ancestors of both apes and humans

Answer: 4. Ancestor of both apes and humans

Origin and Evolution of Man MCQ Question 52. The earliest man-like primate was:

1. Ramapithecus
2. Australopithecus
3. Homo habilis
4. Homo erectus.

Answer: 1. Ramapithecus

Question 53. The first human fossil belonged to:

1. Zinjanthropus
2. Australopithecus
3. Cromagnon man
4. Homo neanderthalensis.

Answer: 2. Australopithecus

Question 54. Fossils of so-called ‘Java Man’ and ‘Peking Man’ belong to:

1. Homo sapiens
2. Homo erectus
3. Homo habilis
4. None of these.

Answer: 2. Homo erectus

Question 55. Anthropoid apes were ancestors of:

1. Monkeys
2. Apes
3. Homo habilis
4. All the apes.

Answer: 1. Monkeys

Origin and Evolution of Man MCQ Question 56. The brain of Australopithecus measured:

1. 350-450 cm³
2. 1400-1450 cm3³
3. 700-900 cm³
4. 800-1400 cm³

Answer: 1. 350-450 cm³

Question 57. Possession of child-like traits by an adult man is called:

1. Gerontomorphism
2. Orthogenomorphism
3. Pedomorphism
4. Foetomorphism.

Answer: 3. Pedomorphism

Question 58. The ancestor of the man who first stood erect was:

1. Australopithecus
2. Java ape man
3. Peking man
4. Cromagnon.

Answer: 1. Australopithecus

Question 59. Cro-magnon was:

1. Carnivorous
2. Omnivorous
3. Herbivorous
4. Frugivorous.

Answer: 1. Carnivorous

Origin and Evolution of Man MCQ Question 60. The first fossils of prehistoric man were discovered by:

1. E. Lewis
2. Raymond Dart
3. Leaky
4. Eugene Dubois.

Answer: 1. E. Lewis

Question 61. Colored rock paintings were presumably first made by:

1. Cromagnon man
2. Neanderthal man
3. Java ape man
4. Peking man.

Answer: 1. Cromagnon man

Question 62. The earliest man who used tools was:

1. Homo habilis
2. Homo erectus
3. Java man
4. Peking man.

Answer: 1. Homo habilis

Question 63. The characteristics of modern man are:

1. Small teeth without huge canines and slight curvature of the vertebral column
2. A flattened face without muzzle and brow ridges
3. Rounded skull with downward-looking foramen magnum
4. All of these

Answer: 1. Small teeth without huge canines and slight curvature of the vertebral column

Question 64. The first evidence of the ceremonial burial of the dead has been found with fossils of

1. Cromagnon man
2. Java ape man
3. Nemuleillial man
4. Peking man.

Answer: 1. Cromagnon man

Question 65. Loss of pigmentation, slender body, reduced appendages, and absence of visual organs are adaptations in:

1. Cave animals
2. Aquatic animals
3. Ailmreal animals
4. Burrowing animals

Answer: 1. Cave animals

Evolution NEET Practice Questions MCQs Question 66. Modem man, Homo sapiens sapiens began spreading all over the globe some:

1. 10000 years ago
2. 150000 years ago
3. 20000 years ago
4. 25000 years ago

Answer: 1. 10000 years ago

Question 67. According to the geological chronology, man belongs to which era

1. Mesozoic
2. Palaeozoic
3. Piepalaeozoic
4. Coenozoic.

Answer: 4. Coenozoic.

Question 68. “Piltdown man” was:

1. Earlier specimens of fossil bones of a man found in Pilldown
2. Skull of Neanderthal man found in Germany
3. Skull and leg bones of Australopithecus
4. A fake assemblage of bones of the skull.

Answer: 4. A fake assemblage of bones of the skull.

Question 69. A pertinent example where die study of human trials has helped in understanding evolution is:

1. Congenital diseases
2. Eye colour
3. Blood groups
4. Chromosomal variations.

Answer: 3. Blood groups

Question 70. DNA matching has shown human beings to be nearest to:

1. Chimpanzee
2. Gorilla
3. Gibbon
4. Rhesus Monkey.

Answer: 1. Chimpanzee

Question 71. Orthognalhotis face occurs in:

1. Homo sapiens
2. Gorilla
3. Ramapilhecus
4. Homo habilis

Answer: 1. Homo sapiens

Evolution NEET Practice Questions MCQs Question 72. Simian gap is;

1. Distance between two nostrils
2. Small diastema
3. The gap between nostrils and upper lip
4. None of the above.

Answer: 2. Small diastema

Question 73. Which of the following primates is the closest relative to modern man

1. Orangutan
2. Sinanthropus
3. Gibbon
4. Gorilla.

Answer: 2. Sinanthropus

Question 74. The earliest man-like primate and oldest of man’s ancestors which is in direct line with human evolution is:

1. Oreopilhecus
2. Proconsul africanus
3. Ramapilhecus
4. Australopithecus.

Answer: 2. Proconsul africanus

Question 75. The fossil of the first known ape is:

1. Dryopilhccus
2. Oreopilhecus
3. Propliopithecus
4. Ramapilhecus.

Answer: 3. Propliopithecus

Question 76. Which of the following is the fossil of the first man-ape

1. Australopithecus
2. Ramapilhecus
3. Homo credits
4. Peking man.

Answer: 1. Australopithecus

Evolution NEET Practice Questions MCQs Question 77. Who said that the human body is a walking museum of antiquities

1. Wejsmann
2. Wiedersheim
3. Wollman
4. Wilkins.

Answer: 2. Wiedersheim

Question 78. Who wrote the first book on human origin

1. Aristotle
2. Linnaeus
3. Huxley
4. Darwin.

Answer: 3. Huxley

Question 79. Outwardly directed widely separated nostrils occur in:

1. Gorilla
2. New World Monkeys
3. Loris
4. Apes.

Answer: 2. New World Monkeys

Question 80. The fire was first used for protection and cooking by:

1. Java man
2. Neanderthal man
3. Peking man
4. Cromagnon.

Answer: 2. Neanderthal man

Question 81. The features not in the direction of the evolution of the human species are:

1. Raised orbital ridges
2. Binocular vision
3. Opposable thumb
4. None of the above.

Answer: 1. Raised orbital ridges

Question 82. In gorillas, great apes, and chimpanzees, the number of chromosomes is:

1. 2N = 46
2. 2N = 44
3. 2N = 48
4. None of these.

Answer: 3. 2N = 48

Question 83. Dryopilhccus occurred:

1. 50 million years ago
2. 50 billion years ago
3. 24 billion years ago
4. 24 million years ago.

Answer: 4. 24 million years ago.

Question 84. What is the brain size of a man?

1. 350-450 cm³
2. 850-950 cm³
3. 1400-1450 cm³
4. 1800-1850 cm³

Answer: 3. 1400-1450 cm³

Question 85. Dubois in 1891 found the fossil of Java ape man. It is:

1. Sinanthropus pekinensis
2. Pithecanthropus erectus
3. Homo rhodesincsis
4. Homo sapiens.

Answer: 2. Pithecanthropus erectus

Question 86. The smallest cranial capacity is that of the:

1. Modern man
2. Cromagnon man
3. Neanderthal man
4. Java man.

Answer: 4. Java man.

Question 87. The smallest cranial capacity is that of the:

1. Modern man
2. Cro-magnon man
3. Neanderthal man
4. Java man.

Answer: 4. Java man.

Question 88. Cranial capacity was highest in:

1. Java man
2. Cromagnon
3. Neanderthal man
4. Peking man.

Answer: 2. Cromagnon

Question 89. Which of the following fossil man possessed a cranial capacity almost equal to that of modern man

1. Neanderthal man
2. Java ape man
3. Peking man
4. Australopithecus alricans.

Answer: 1. Neanderthal man

Question 90. Match the following lists and give the correct answer from the code given below the lists.

Answer: 2

Question 91. Which of the following is correct?

1. Australopithecus is the real ancestor of modern man
2. Cromagnon man’s fossil has been found in Ethiopia
3. Homo erectus is the ancestor of man
4. Neanderthal man is the direct ancestor of Homo sapiens.

Answer: 3. Homo erectus is the ancestor of man

Question 92. The age of the fossil of Dryopithecus on the geological time scale is:

1. 75 x 10⁶ years back
2. 2.5 x 10⁶ years back
3. 25 x 10⁶ years back
4. 50 x 10⁶ years back.

Answer: 3. 25 x 10⁶ years back

Evolution NEET Practice Questions MCQs Question 93. The extinct human who lived 1,00,000 to 40,000 years ago, in Europe. Asia and parts of Africa, with short stature, heavy eyebrows, retreating foreheads, large jaws with heavy teeth, stocky bodies, a lumbering gait, and stooped posture were:

1. Neanderthal human
2. Cro-Magnan humans
3. Ramapithecus
4. Homo habilis.

Answer: 1. Neanderthal human

Question 94. Homo sapiens evolved during

1. Pleistocene
2. Oligocene
3. Pliocene
4. Miocene

Answer: 1. Pleistocene

Question 95. Which of the following is the closest relative of man?

1. Chimpanzee
2. Gorilla
3. Orangutan
4. Gibbon

Answer: 1. Chimpanzee

Question 96. Which of the following is the correct order of the evolutionary history of man?

1. Peking man. Homo sapiens, Neanderthel man, Cromagnon man
2. Peking man. Neanderthal man, Homo sapiens, Cromagnon man
3. Peking man, Hedalberg man, Neanderthal man, Cromagnon man
4. Peking man, Neanderthal man, Homo sapiens, Hedalberg man

Answer: 3. Peking man, Hedalberg man, Neanderthal man, Cromagnon man

Evolution NEET Practice Questions MCQs Question 97. In recent years, DNA sequences of mt-DNA and Y-chromosomes were considered for the study of human evolution, because they:

1. Can be studied from the samples of fossil remains
2. Are small and thus easy to study
3. Are uniparental in origin and do not take part in recombination.
4. Their structure is known in greater detail.

Answer: 2. Are small and thus easy to study

Question 98. Which of the following was the transitional stage between apes and humans:

1. Homo habilis
2. Homo erectus
3. Australopithecus ramidus
4. Australopithecus Africans.

Answer: 3. Australopithecus ramidus

Question 99. Highest cranial capacity is found in:

1. Homo sapiens sapiens
2. Neanderthal man
3. Peking man
4. Cro-magnon man.

Answer: 4. Cro-magnon man.

Question 100. Cromagnon man was:

1. Frugivorous
2. Carnivorous
3. Herbivorous
4. Omnivorous.

Answer: 2. Carnivorous

NEET Biology Nervous System

Systems of Coordination.

1. Nervous system. Fast, specific with the electrochemical transmission, along nerve fibers
2. Endocrine system. Slow, diffused with chemical transmission through body fluids.
3. Immune system (antigen-antibody reactions)
4. Neurology. Study of morphology, physiology, and pathology of the nervous system.
5. Neurophysiology. Physiology or working of the nervous system.

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Nervous System NEET Notes

NEET Biology Role Of The Nervous System

1. The nervous system illustrates the activities of different organs and the entire organism.
2. The nervous system links the various organ systems and coordinates all their activities.
3. It ensures the integrity of the organism.
4. The unity of an organism and its internal environment is affected and maintained through the nervous system.
5. Man’s brain is the material basis of thinking, memory, and good speech.
6. It stimulates or inhibits the activities of muscles and glands to evoke a response to the received information.
7. Special senses such as vision, hearing, smell, taste, and touch produced by information provided by sense organs are associated with the nervous system.

NEET Biology Nervous System Neuron

1. The fundamental components of nervous tissue are neurons, which originate from the ectoderm. Each neuron comprises a cell body, or cyton, containing a nucleus and many nerve fibers, classified into two categories.
2. An axon is an efferent process as it transmits impulses outward. The terminal branches of the axon, known as telocentric, possess end knobs that release neurotransmitters facilitating impulse conduction.
3. The branching processes of dendrites are afferent as they receive impulses for the neuron.
4. Nerve impulses are transmitted from the axon terminals of one neuron to the dendrites of another. The convergence of the two is referred to as a synapse.

NEET Biology Constituents Of the Nervous System

1. A central nervous system is composed of the brain and spinal cord. It contains nerve centers for all sensations. The brain and spinal cord are covered by protective membranes called meninges and their cavities are filled with cerebrospinal fluid.
2. The peripheral nervous system consists of various nerves which conduct impulses to all parts (Spinal and Cranial nerves).
3. The autonomic nervous system illustrates the working of viscera composed of sympathetic and parasympathetic nervous systems.
4. The central nervous system is made of nerve bodies forming the grey matter and of nerve fiber tracts which form the white matter.
5. The peripheral nervous system consists of nerves made of nerve fibers and nerve cell bodies located in the brain, spinal cord, and ganglia.
6. The autonomic nervous system consists of nerve cell bodies, their nerve fiber, and nerve plexies. However, all three divisions of the nervous system are connected intimately both structurally and functionally.

Structure And Function Of Neurons NEET

Brain. The brain reaches its highest development in mammals with better intFor exploration and mastery over the environment. The cerebral hemisphere reaches the status of a dominant inter-example rating part of the brain and acts as a coordinating center of the brain.

1. The cerebral hemispheres are immense projecting forwards above the olfactory lobes and backward above the diencephalon and mid-brain. The two hemispheres are separated by it deep median fissure.
2. Each hemisphere is further divided In an oblique Sylvimi (IsMire into an anterior frontal lobe and a posterior lateral temporal lobe
3. The cerebrum or cerebral hemispheres have a thick roof called a ‘neopallium’ in mammals, it is formed by upgrowth of the lateral portions of the pallium, but it differs histologically from the pallium in having a larger number of neurons which are arranged in layers of the cortex and medulla.
4. The cortex is further increased by many curved depressions or sulci and lobes or ‘gyri’ (absent in rabbits). Each hemisphere has a complex lateral ventricle, each ventricle has a middle body from which three prolongations come run forward, backward, and outward.
5. Above the lateral ventricles is a band of nerve fibers called corpus callosum which joins the neopallium or cortex of the two cerebral hemispheres, the anterior part of the corpus callosum is bent to form ‘menu while the posterior part is bent downwards and forwards forming splenium.
6. Below the corpus callosum is a band of longitudinal fibers forming the ‘fornix’. Its main body is formed by the union of two sets of fibers called fimbriae or taeniae hippocampi. Between the corpus callosum and fornix is a septum peculium having a small cavity called pseudocoel or 5th ventricle, which is not a true ventricle but a space between the two hemispheres.
7. The floor of the hemispheres forms anterior corpora striata and postero-lateral hippocampus which serves as an olfactory center, the median commissure of it is called psalterium or lyra, and that of corpora striata is the anterior commissure.

1. Running from the anterior commissure to the optic chiasma is a delicate membrane of the lamina terminals which marks the anterior boundary of the 3rd ventricle.
2. The cerebral hemispheres receive impulses from visual, auditory, olfactory, tactile, and peripheral receptors and they initiate voluntary motor impulses which are carried by bundles of nerve fibers to muscles. The cortex For exampleates the impulses and organizes and for example, rates them into coordinated activities.
3. The diencephalon is small and hidden dorsally by the hemispheres, it has a laterally compressed third ventricle or diaconal whose roof is formed by a delicate velum interpositum.
4. The side walls of the diencephalon or optic thalami are made of a thick mass of white and grey matter on the external surface of each thalamus near the anterior end is a rounded corpus geniculatum. The floor of the diencephalon is called the hypothalamus.
5. Recently a potent substance called hypothalamic D has been extracted from the hypothalamus which stimulates the production of adrenotrophic hormone of the pituitary gland.
6. The hypothalamus is composed of four parts optic chiasma, infundibulum and tuber cinereum, pituitary gland, and corpus albicans.
7. The diencephalon is a relay center of impulses from the posterior For example going to the cerebral cortex, the thalami are the centers of exploration and activity and for recognition of sensations of heat, cold, pain, and body movements.
8. Mid brain has two pairs of optic lobes called corpora quadri gemina. The floor of the mid brain is called crura cerebral which contains bundles of fibers. The canal which connects the 3rd ventricle with the 4th ventricle is called iter. Vision is controlled by the cerebrum and anterior parts of the anterior optic lobes.
9. The posterior optic lobes are auditory in function. The highly developed cerebellum is divided to form five lobes, central lobe vermis, two lateral lobes, and two outer floccular lobes.
10. In section, the cerebellum shows an outer thick layer of grey matter and a central mass of white matter, the two exhibit a tree-like pattern called arbor vitae.
11. The cerebellum is concerned with equilibrium and co-ordination of muscles and responses initiated by the cerebral hemispheres and carried out through the cerebellum Medulla oblongata lias a posterior choroid plexus below which is the fourth ventricle joined in front to the iter and behind to the central canal.
12. The medulla controls respiration, heartbeat, and blood vessels, it also has conduction pathways for impulses passing from cerebral hemispheres to the spinal cord and again in the opposite direction.

Central And Peripheral Nervous System NEET Study Material

NEET Biology Nervous System Spinal Cord

1. It is a cylindrical, cord-like, homogeneous extension of the medulla oblongata, measuring 42 to 45 cm in length and 2 cm in thickness in humans, extending from the neck to the lumbar region.
2. For instance, it traverses the neural canal of the spinal column and culminates in a slender extension known as the filum terminale. Growth ceases around 4 to 5 years of age.
3. In this structure, the white matter is located externally, while the H-shaped grey matter is situated internally, which is the inverse of the brain’s configuration.

NEET Biology Nervous System Peripheral

1. Cranial nerves. The peripheral nervous system consists of nerves connected to or arising from the central nervous system, it has cranial and spinal nerves. Twelve cranial nerve 1 – Olfactory (sensory). 11-Optic (sensory), lH-Oculomotor (motor), IV-Trochlear (motor), V-Trigeminal (mixed ), Vl-Abducens (motor), Vll-Facial (mixed), VIII-Auditory (sensory), IX- Glossopharyngeal (mixed), X-Vagus (mixed), Xl-Spinal accessory and XII-Hypoglossal (motor).
2. Sensory Cranial Nerves. Olfactory, Optic, and Auditory.
3. Motor Cranial Nerves. Oculomotor, Pathetic/Trochlear, Abducens, Accessory Spinal and Hypoglossal.
4. Mixed Cranial Nerves. Trigeminal, facial, Glossopharyngeal and Vagus,
5. Dentist’s nerves. Trigeminal (Vth nerve) [Has a swelling called gasserian ganglion from where it divides into 3 branches]
6. Number of Cranial Nerves. 10 pairs in amniotes (fishes and amphibians) and 12 pairs in amniotes (reptiles, birds, and mammals).
7. The facial nerve in frogs passes through the Gasserian ganglion but in mammals, it passes out through the Geniculate ganglion.
8. Glossopharyngeal and Vagus nerves in frogs pass out through the jugular ganglion but in mammals, they pass through the vagus ganglion. All are situated within the cranium.
9. The motor component of the vagus nerve controls sound production.

NEET Biology Nervous System Spinal Nerves

1. They originate from the spinal cord. Humans possess 31 pairs of spinal nerves.
2. Each spinal nerve comprises two roots: sensory (afferent) and motor (efferent) roots.
3. All spinal nerves possess a mixed composition. Each spinal neuron is partitioned into three rami.
4. The filum terminale and several posterior spinal nerves create a horse-tail-like structure known as the cauda equina within the neural canal.

NEET Biology Nervous System Multiple-Choice Questions

Question 1. Some Cells In Our Body Can Be Over A Foot Long, Are :

1. The Muscle Cells
2. The Bone Cells
3. The Nerve Cells
4. Gland Cells.

Answer: 3. The Nerve Cells

Question 2. Power Of Regeneration Is Lowest In :

1. Brain Cell
2. Liver Cell
3. Bone Cell
4. Muscle Cell.

Answer: 1. Brain Cell

Question 3. Nervous System Is Concerned With Two Important Functions :

1. It Regulates The External Environment And Responds To Internal Environment Through Sense Organs
2. It Regulates The Internal Environment And Responds To the External Environment Through Sense Organs
3. It Regulates The External Environment And Responds To Internal Environment Through Motor Nerve
4. It Regulates The Internal Environment And Responds To the External Environment Through Motor Nerves.

Answer: 4. It Regulates The Internal Environment And Responds To the External Environment Through Motor Nerves.

Question 4. A Neuron Is :

1. Structural And Functional Unit Of The Nervous System
2. Structural And Functional Unit Of The Endocrine System
3. Structural And Functional Unit Of The Muscular System
4. Structural And Functional Unit Of Skeletal System.

Answer: 1. Structural And Functional Unit Of The Nervous System

Important NEET MCQ On Nervous System Question 5. Synapse Is A Term To Denote The :

1. Connection Between Two Arteries
2. Connection Between Two Veins
3. Connection Between Two Neurons
4. Connection Between Two Lungs.

Answer: 3. Connection Between Two Neurons

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Question 6. The Sympathetic And Parasympathetic Systems Constitute :

1. Reflex Arc
2. Reflex Action
3. Autonomic Nervous System
4. Peripheral Nervous System.

Answer: 3. Autonomic Nervous System

Question 7. The Central Nervous System Includes :

1. Brain And Spinal Cord
2. Spinal Nerves And Spinal Cord
3. Brain And Pineal Body
4. Only the Cerebrum And Medulla Oblongata Of the Brain.

Answer: 1. Brain And Spinal Cord

Question 8. The Central Nervous System; Cranio-Spinal System; Autonomic System And Receptor System In A Vertebrate Collectively Form:

1. Nervous Systempiamater
2. Circulatory And Nervous Systems
3. Reproductive And Nervous Systems
4. Digestive And Sympathetic Systems.

Answer: 1. Nervous Systempiamater

Question 9. The brain In a Frog Is Contained In the Cranium, Enveloped By a Connective Tissue Membrane Called :

1. Cranial Membrane
2. Meninges
3. Pericardium Membrane
4. Pia mater

Answer: 4. Pia mater

Important NEET MCQ On Nervous System Question 10. The Brain Is Surrounded By An Outer Fibrous, Non- Vascular Membrane Called :

1. Pia mater
2. Neuromancer
3. Myomater
4. Dura mater.

Answer: 1. Pia mater

Question 11. The Inner Membrane surrounding the Brain Is :

1. Thin And Cartilaginous Pia mater
2. Thick And Muscular Pia mater
3. Thin And Vascular Pia mater
4. Thin Cardiac Membrane.

Answer: 3. Thin And Vascular Pia mater

Question 12. Pineal Stalk, A Slender Tubular Structure Arises From :

1. Ventral Surface Of Diencephalon
2. Dorsal Surface Of Diencephalon
3. Both Dorsal And Ventral Surfaces Of Diencephalon
4. Antero-Ventral Surface Of Diencephalon.

Answer: 2. Dorsal Surface Of Diencephalon

Question 13. Optic Chiasma Is Formed By The Crossing Over Of Two :

1. Olfactory Nerves
2. Oculomotor Nerves
3. Trochlear Nerves
4. Optic Nerves.

Answer: 4. Optic Nerves.

Question 14. Hypothalamus Forms The Floor And Lower Part Of :

1. Diacoel
2. Optocoel
3. Lateral Ventricle
4. Fourth Ventricle.

Answer: 1. Diacoel

Important NEET MCQ On Nervous System Question 15. Two-Thirds Of Entire Brain Is Made Of:

1. Cerebellum
2. Medulla Oblongata
3. Flocculus
4. Cerebrum (Cerebral Hemisphere).

Answer: 4. Cerebrum (Cerebral Hemisphere)

Question 16. In Mammals, The Two Lobes Of the Cerebral Hemisphere Are Connected By a Large Distinctive Transverse Fibrous Bridge Of White Matter Called:

1. Corpus Spongiosum
2. Corpus Callosum
3. Corpus Commissures
4. Cerebral Connective.

Answer: 2. Corpus Callosum

Question 17. Cell Bodies Of Neurons Bringing Afferent Information Into the Spinal Cord Are Located In the:

1. Dorsal Root Ganglia
2. Ventral Root Ganglia
3. Grey Matter Of Spinal Cord
4. White Matter Of Spinal Cord.

Answer: 1. Dorsal Root Ganglia

Question 18. In the Brain, Crura Cerebri Is A Structure Made Of:

1. Two Large Bands Of Nerve Fibres
2. Four Large Bands Of Nerve Fibres
3. Six Bands Of Nerve Fibres
4. Eight Bands Of Nerve Fibres.

Answer: 1. Two Large Bands Of Nerve Fibres

Question 19. The Roof Of Medulla Oblongata Is Thin And Piamater In This Portion Is Greatly Folded, Richly Vascular, And Pushed Into the Cavity Of the Medulla As :

1. Anterior Choroid Plexus
2. Posterior Choroid Plexus
3. Corpora quadrigemina
4. Optic Thalami

Answer: 2. Posterior Choroid Plexus

Nervous System Recommended MCQs NEET Questions Question 20. The Ventricles Of the Brain And Central Canal Of the Spinal Cord Arc Filled With A Fluid Called :

1. Cerebro-Spinal Fluid
2. Spinal Fluid
3. Cranial Fluid
4. Pericardial Fluid.

Answer: 1. Cerebro-Spinal Fluid

Question 21. Olfactory Lobes Of Human Are :

1. Fully Solid
2. Half Hollow And Half Solid
3. Fully Hollow
4. Become Solid At Puberty.

Answer: 1. Fully Solid

Question 22. Nissl Granules In The Nerve Cell Bodies Are Actually :

1. Deep Staining Mitochondria
2. Lysosomes
3. Coiled Condensed Elements Of Rough Endoplasmic Reticulum
4. Multiple Number Of Golgi Bodies.

Answer: 3. Coiled Condensed Elements Of Rough Endoplasmic Reticulum

Question 23. The Anterior Choroid Plexus Is Located In Or Near The :

1. Diencephalon
2. Optic Lobes
3. Cerebrum
4. Cerebellum.

Answer: 1. Diencephalon

Question 24. The Pineal Body Is Considered As :

1. An Endocrine Gland
2. An Organ Concerned With Voluntary Action
3. An Organ Concerned With Vision
4. A Vestige Of 3rd Eye And Endocrine Gland.

Answer: 4. A Vestige Of 3rd Eye And Endocrine Gland.

Nervous System Recommended MCQs NEET Questions Question 25. If the Cerebral Hemispheres Of the Frog Are Removed, It:

1. Dies Immediately
2. Stops Feeding
3. Dies After Some Time
4. Behaves Normally.

Answer: 2. Stops Feeding

Question 26. In Human Brain, Corpora Quadrigemina Represents :

1. Fore Brain
2. Mid Brain
3. Hind Brain
4. Spinal Cord.

Answer: 2. Mid Brain

Question 27. The Cavity Of Spinal Cord Is Called :

1. Blastocoel
2. Enterocoel
3. Schizocoel
4. Central Canal.

Answer: 4. Central Canal.

Question 28. Brain Develops From :

1. Ectoderm
2. Mesoderm
3. Endoderm
4. Both Ectoderm And Endoderm.

Answer: 1. Ectoderm

Question 29. The Function Of the Central Nervous System :

1. Controls Various Functions Of the Body
2. Directs Various Functions Of Body
3. Controls And Co-Ordinates The Activities Of Body
4. Conducts Impulses From One Part To The Other.

Answer: 3. Controls And Co-Ordinates The Activities Of Body

Nervous System MCQ for NEET Question 30. Corpora Striata Is A Part Of:

1. Cerebellum
2. Pons
3. Cerebrum
4. Fomix.

Answer: 3. Cerebrum

Question 31. Foramen Of Monro In Brain Is An Aperture Between :

1. Diacoel And Metacoel
2. Rhinocoel And Diacoel
3. 3rd And 4th Ventricle
4. Lateral And Third Ventricle.

Answer: 4. Lateral And Third Ventricle.

Question 32. Which Part Of The Brain Controls Muscular Coordination?

1. Cerebrum
2. Cerebellum
3. Medulla Oblongata
4. Diencephalon.

Answer: 2. Cerebellum

Question 33. A Deep Longitudinal Fissure Divides The Cerebrum :

1. Into Six Hemispheres
2. Into Four Hemispheres
3. Into Two Hemispheres
4. Into Eight Hemispheres.

Answer: 3. Into Two Hemispheres

Question 34. The Dendrites Of A Typical Vertebrate Motor Neuron, Compared To The Neuron’s Axon Arc Generally :

1. Longer
2. Larger In Diameter
3. More Branched
4. More Myelinated.

Answer: 3. More Branched

Nervous System MCQ for NEET Question 35. The Parts Of Neurons That Perform Basic Cellular Functions, Such As Protein Synthesis, Are The :

1. Axons
2. Dendrites
3. Somas
4. Synaptic Knobs.

Answer: 3. Somas

Question 36. The Medulla Oblongata Continues As the Spinal Cord Which Runs In The Canal Of The :

1. Vertebral Column
2. Mid-Brain
3. Pituitary
4. Corpus Callosum.

Answer: 1. Vertebral Column

Question 37. It Is Said Injury To the Brain Is Permanent And Nerve Cells Cannot Rfor Exampleenerate. The Reason Is :

1. Absence Of Nucleus
2. Cells Are Very Long
3. They Lack Chromosomes
4. Part Of Chromatin Lies Outside The Nucleus.

Answer: 2. Cells Are Very Long

Question 38. Regulation Of Heart Beat And Respiration Is Controlled By:

1. Cerebrum
2. Cerebellum
3. Medulla
4. Pons Varolii.

Answer: 3. Medulla

Question 39. The Volume Of Blood Supplied To The Brain Per Minute Is:

1. 1000 ml
2. 560 ml
3. 350 ml
4. 400 ml

Answer: 3. 350 ml

Nervous System MCQ for NEET Question 40. The third Ventricle Of a rabbit’s Brain Is Called :

1. Rhinocoel
2. Rhombocoel
3. Diacoel
4. Metacoel.

Answer: 3. Diacoel

Question 41. Learning Is Related To Which Part Of Human Brain?

1. Hypothalamus
2. Medulla
3. Cerebrum
4. Cerebellum.

Answer: 2. Medulla

Question 42. Thermo-Regulatory Centre In The Body Is :

1. Spinal Cord
2. Hypothalamus
3. Cerebellum
4. Pituitary.

Answer: 3. Cerebellum

Question 43. The Ganglion From Which Trigeminal Nerve Arises Is Called :

1. Vagus Ganglion
2. Cervical Ganglion
3. Neuroglia
4. Gasserian Ganglion.

Answer: 4. Gasserian Ganglion

Question 44. The Maximum Number Of Meninges In Animals Is/Are :

1. One
2. Two
3. Three
4. Four.

Answer: 2. Two

MCQ On Nervous system NEET Question 45. Foramen Of Magnadie Is Found In :

1. Optic Lobes
2. Crura Cerebri
3. Medulla Oblongata
4. Iter.

Answer: 3. Medulla Oblongata

Question 46. When Action Potential Jumps From One Node Of Ranvier To The Next, It Is Termed As :

1. Passive Conduction
2. Active Conduction
3. Saltatory Conduction
4. Neurotransmission.

Answer: 3. Saltatory Conduction

Question 47. Match The Type Of Respirator On The Right With Sense Organs Listed On The Left:

1. 1-A  2-B   3-C  4-C   5-D
2. 1-A  2-B   3-D  4-E   5-C
3. 1-B  2-A   3-E  4-C   5-D
4. 1-A  2-B   3-C  4-D   5-C.

Answer: 1. 1-A  2-B   3-C  4-C   5-D

MCQ On Nervous system NEET Question  48. The Sensory Neuron Transmits Patterns Of Action Poiemials That Indicate :

1. The Type Of  Stimulus Received
2. The Intensity Of Stimulus Received
3. The Source Of The Stimulus
4. Both 2 And 3.

Answer: 4. Both 2 And 3.

Question  49. A Receptor That Detects The Position Of Parts Of Tire Body Is Called :

1. A Proprioceptor
2. A Hair Cell
3. A Mechanorcceptor
4. A Muscle Spindle.

Answer: 1. A Proprioceptor

Question  50. Regulatory Control Or Deep Body Temperature, Osmoregulation. Thirst And Hunger Occur In The :

1. Anterior Colliculi
2. Hypothalamus
3. Thalamus
4. Cerebellum.

Answer: 2. Hypothalamus

NEET Biology Organisms And Population Ageing And Death

NEET Biology Organisms And Population Ageing And Death Growth

• Growth: It refers to the augmentation in size and mass of an organism resulting from the synthesis of protoplasmic and apoplastic components. The event occurs when anabolism predominates in the overall metabolic process. There are three types of growth.
• Auxetic growth: In this instance, the volume of the organism expands due to the proliferation of body cells without an increase in the number of cells. The quantity of cells is predetermined in the majority of bodily regions. This sort of growth occurs in worms, rotifers, and a category of early chordates known as tunicates.
• Multiplicative growth :In this scenario, the cell count grows while the average cell size remains constant. All occurring decisions are mitotic. It frequently manifests in embryos and is a defining feature of the prenatal development of higher vertebrates.
• Accretionary growth refers to the mitotic division of reserve cells to augment and substitute the depleted differentiated cells.
• The various cells in the post-embryonic phase lose their ability to divide, resulting in this form of growth, for example. Development of epidermal cells from the Malpighian layer.
• Appositional growth: it entails the accumulation of new layers onto already established layers. It is a distinctive way of growth for stiff materials.

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NEET Biology Organisms And Population Ageing And Death Growth Rate

All creatures develop at a certain rate and cadence. The growth is a noticeable and quantifiable increase in the bulk of living material, which can be assessed by weighing at intervals.

Furthermore, the growth rate is variable, as organisms develop at distinct rates throughout different intervals. Rapid growth occurs throughout prenatal and teenage stages, which then decelerates during juvenile and post-adolescent phases, ultimately ceasing thereafter.

Organisms And Population Ageing And Death NEET Notes

NEET Biology Organisms And Population Ageing And Death Growth Curve

The growth of an animal organ for a definite period when plotted against time forms a S-shaped Sigmoid curve. it is called a growth curve.

• An analysis of the Sigmoul curve shows ills’ glow it is slow in llu[•Birds and mammals stop growing when they have attained a certain characteristic age and size.
• it has been found that the factors that check the unlimited growth of animal tissues are many and varied. One such mechanism is the intrinsic antagonism between the factors that regulate the process of proliferation.
• The initial and final weight of an individual for any period of tune is lowed absolute prow lit. l.i Cell uniw3 Grow the old cells’ events during the inter of the cell cycle.
• During this phase, new materials such as nucleic acids, proteins, and protoplasmic bodies were formed. interphase is completed in three phases G, S and G, phases. Cell growth is an utmost important factor in the growth of multicellular animals. Cell growth leads to the division of cells also. Cell growth cannot be measured because of the small size and location of the cell.

1. Pattern Of Growth:

• Isometric growth: in this pattern of growth, an organ grows at the same mean rate as the rest of the body c.y. fishes and certain insects like locusts.
• Allnnictric growth: in this pattern of growth, an organ grows at a rate different from that at which the body grows mammals.

2. Methods Of Growth: Growth in animals is accomplished by several methods.

The most important of these are:

• Protoplasmic synthesis: Through this process, the growing animal synthesizes new l4ing matter from available food materials. The new raw materials are obtained from the digestion and absorption of complex food materials such as proteins, carbohydrates and lipids.
• Uptake of water: The amount of water that accumulates in the animal body during growth and development is enormous.
• intercellular deposition; Large-scale intercellular deposition of non-living matter occurs during growth. These substances consist mostly of jelly, fibres or the ground substances of cartilage and bone.

Organisms And Population Ageing And Death NEET Notes

NEET Biology Organisms And Population Ageing And Death Hormonal Control Of Growth Rate in Man

• Thymosin hormone, released by the thymus gland, affects growth during the ages of 10 to 13 years (childhood).
• This era is characterized by sluggishness. Thyroxine and somatotropic hormone (STH) enhance development rate throughout late childhood.
• Growth accelerates throughout puberty (ages 14 to 18 years) due to heightened secretory activity of the pituitary and other endocrine glands.
• In males, testosterone regulates the development of secondary sexual organs and accessory sex traits, whereas in females, progesterone and estrogen perform similar functions.

NEET Biology Organisms And Population Ageing And Death Growth Factors

1. Epidermal Growth Factor (EGF): it stimulates epithelium to undergo mitosis – EGF is produced under the scab and is also produced in the sal4ary glands.
2. Fibroblast growth Factor (FGF): it stimulates the division of endothelial cells to heal the injured blood vessels.
3. Platelet-der4ed Growth Factor (PGF): it stimulates the mitosis of fibroblasts at the injured site to fill in the damaged area under the blood clot.

Measurement of Growth

• The amount of growth, an animal undergoes is expressed in terms of absolute growth or relative growth.
• The absolute growth rate is the increase in growth per unit of time.
• The relative growth rate is a relative increase in growth per unit of time. Comparisons of relative growth rates show many interesting patterns in animal growth.

Grow th Arresting Factors

• Birds and mammals stop growing when they have attained a certain characteristic age and size.
• it has been found that the factors that check the unlimited growth of animal tissues are many and varied. One such mechanism is the intrinsic antagonism between the factors that regulate the proliferation process.
• Another check on growth is cell destruction. Another mechanism is the hormonal cessation of growth in the long hones.

NEET Biology Organisms And Population Ageing And Death Regeneration

Regeneration, The ability of a living organism to replace out parts, regrow cast tY organs and transform the entire body from small fragments of it is called regeneration.

Categories of animal regeneration :

1. Restorative regeneration.
2. Restorative regeneration.

1. Restorative regeneration:  It is a common phenomenon amongst invertebrates and vertebrates. in sponges, an entire sponge may regenerate and form a group of a few cells. Similarly in Hydra, small pieces containing both germ layers may regenerate into new organisms.

Different Animal groups and their Regenerative body parts

Ageing And Death In Organisms NEET Study Material

2. Reparative regeneration: It is quite common in the case of invertebrates and vertebrates. Amongst vertebrates, it is best observed in the Axolotl larva which can replace its tail, limbs and eyes. Tadpole the frog also shows a similar type of regeneration. Lizards can regenerate their tails but they are without bones. L4er in man has great power of reparative regeneration.

• Physiological regeneration: Replacement of cells of the body which are worn out due to constant activities.
• Compensatory hypertrophy: The regeneration of internal organs by enlarging one of the paired organs in case one is lost accidentally e.g. kidney
• Heleromorphosis: Regeneration that produces a part different from a lost part, e.g. crayfish.
• Mechanism of regeneration: given by T.H. Morgan

1. Morphallaxis: It is the reconstruction of an entire animal from a small fragment by reorganization of the existing cells.
2. Epimorphosis: It replaces a lost organ of the body by the proliferation of new cells from the surface of the injured part.

NEET Biology Organisms And Population Ageing And Death Ageing

• Gerontology: The field of developmental biology which deals with the study of the process of ageing is known as gerontology. it is the progress or deterioration in the structure and functions of cells, tissues and organs of the organism with time. it leads to death.
• Ageing: it is progress4e deterioration in this structure ami functions of cells, tissues, of pans ami organ systems. There is a progress decline in metabolism’s ability to replace worn-out cells, repair damaged tissues and resistance to diseases.

As old age progresses, skin becomes dry, and wrinkled, hair falls off, the body assumes a stooping posture, bones become brittle, and muscles, skin and cartilage become less elastic. Ageing affects the blood-vascular system. Sense organs like an ear. eyes etc. lose their intensities and kidney tubules are no more efficient
in the production of normal urine.

1. The heart pumps 35% less blood and sends 20% and 58% less blood to the brain and kidneys.
2. Oxygen carrying capacity of blood reduces.
3. The formation of new RBCs from the bone marrow slows down.
4. Calcium accumulates in the blood.

Cellular changes during ageing

1. There occurs reduction in tbe granular endoplasmic reticulum, partial degeneration of mitochondria (According to Rafsksy and Brarrows i958) and accumulation of lipofuscin granules.

1. Somatic mutations occur in, tbe cells of l4er, brain, heart and stomach.
2. Certain enzymes like aldolase, acctyl-cholincstrase, lactase dehydrogenase, glucose 6- phosphate dehydrogenase show reduced act4ities.
3. The number of chromosomes changes from the normal. Thus there are changes in DNA structure. in mice, dog and man, with increase in age, the l4er cells exhibit increased number of chromosomal aberrations,
4. Cellular membranes come to have calcium deposition, (According to Shock and Strehler i962) thus do not show select4e permeability.
5. Due to storage of certain pigments, the rate of cell d4ision decreases.

Extracellular changes: Extracellular changes include structural and functional changes in collagen.Collagen is most abundant extracellular protein which with ageing becomes less permeable, less flexible and insoluble. These changes interfere the normal functioning of the cells and induce the ageing.

Changes at the organ level include structural changes in the skin, muscles, bones etc. and also physiological changes in the vital organs like the heart, brain, kidney etc

NEET Biology Organisms And Population Ageing And Death Theories Of Ageing

1. The exact reason behind ageing is not clearly understood, and it is considered a cyclic phenomenon in one’s life. Several hypotheses have been proposed to explain the reason for ageing. They are as follows :
2. According to one view, free radicals accumulate with age which brings about oxidant reactions resulting in the deterioration of collagen and elastin etc. The oxidation of unsaturated fats results in the impairment of cell membranes in their select4e permeability.
3. The immunity system breaks down since the capacity of the formation of lymphocytes by bone marrow is lessened.
4. Ageing reduces the sensibility and effectiveness of the nervous control over the endocrine glands.
5. The high rate of metabolism results quickening of old age. probably CrT in,hc coded message of DNA increases due to old age which affects proper protein synthesis.
6. The tendency of ageing is intrinsic i.c. an organism will undergo ageing at a rat determined by the nature of genes.

Whatever views have been proposed, even today the understanding of the reasons for old age remains vague.

Ageing And Death In Organisms NEET Study Material

Degrowth and death factors which result in degrowth

• The rate of breakdown surpasses that of synthesis reactions within the body.
• Internal reserves, shown as fat in adipose tissue, are metabolized to supply energy for essential living functions.
• Proteins from the living materials are also utilized for energy production.
• All these variables contribute to the depletion of living matter and lead to degrowth.
• Lipofuscin is the pigment associated with aging.
• With aging, there is a decrease in body weight by 12%, brain weight by 15%, and liver weight by 37%.
• The basal metabolic rate is 20%, the speed of nerve impulses is 5%, and the renal blood flow is 40%. to the brain is 80%. Consequently, there are few lymphocytes.

NEET Biology Organisms And Population Ageing And Death Death

it is a biological event which is due to a permanent breakdown in body functioning usually occurring due to a lack of oxygen supply to tissues. The cells stop normal functioning. it is an inescapable event of life.

Symptoms of clinical death: Symptoms of clinical death are Heartbeat, pulse and respiration stop 2 Pupils become fixed, remain dilated and do not respond to light.

Two main categories of causes of death

1. Weakening of tissues and vital organs: Weakening of tissues and vital organs, such as the heart, liver, kidney etc. result in physiological and metabolic disorders of irreversible nature. Sudden blockage of blood supply to the heart, and brain causes instantaneous death.
2. Due to ageing, there is a gradual breakdown in the immune system. Thus due to loss of body resistance, in old age man becomes susceptible to infectious diseases.

• Considerable growth occurs during the late embryonic or foetal period in the case of mammals.
• Replacement of old worn-out cells, metamorphosis and regeneration are the three main categories of post-embryonic development.
• Post-embryonic developments are characterised by growth, morphogenesis and differentiation finally. Ageing is also a post-embryonic stage.
• Animals grow at different rates at different periods of life.
• The human embryo is i50 /rm at the time of implantation and grows to about 50 cm during the gestation period.
• Growth may be auxetic or multiplicat4e accretionary. Fibroblast growth factors (FGFs) control cell proliferation in the development of limbs in chick, and insulin-like growth factors (iGFs) have a role in prenatal and postnatal growth of mammals. Growth hormone (Gil) secreted in the anterior lobe of the pituitary plays an important role in growth during childhood.
• Hydra and planaria have a capacity for regeneration. Nematodes show very low regenerat4e ability.
• Glial growth factors (GGFs) and other factors such as (FGFs iGFs) control amphibian limb regeneration.
• Compensatory regeneration: In the case of compensatory regeneration, the cells of l4er or kidney d4ide do not form an undifferentiated mass of cells or tissues, rather produce cells similar to themselves and maintain their function.
• Epimorphic regeneration: In the case of epimorphic regeneration as in Salamander, dedifferentiation occurs, and then these cells divide to form blastema which later on transforms into a correctly patterned limb structure.
• Reparative regeneration: The power of repairing only some body cells e.g. skin layer: gut lining: RBCs of blood etc.
• Morphallactic regeneration: The formation of the whole body from a body fragment by reorganizing the existing cells, e.g. Formation of components body of Hydra from a fragment.

Population Ageing And Death NEET Biology Notes

Changes in the weights of human body parts from birth to adulthood:

Life Span Of Selected Animals:

NEET Biology Organisms And Population Ageing And Death Quanta To Memory

• Vladimir Korenchevsky-Father of gerontology
• Werner Syndrome is a syndrome with signs of advanced ageing in the 20s.
• Eutyly: When the number of cells is constant both for the entire life and specific organs e.g. Ascaris.
• Nucleopycnosis: It is the shrinkage and condensation of chromatin leading to the death of the nucleus.
• Heteromorpliosis: it is a case when the regenerated part is different from the lost part.
• There are 60 quadrillion cells in an average adult human body weighing 60 kg but only 2 quadrillion in an infant.
  From the age of about 30 years, the human body becomes functionally less efficient by about 0.8% every year.
• The nucleus shrinks and stains deeply with advancing age. This is due to condensation of chromatin and leads to cellular death. Such a degenerat4e process is called nuclear pyknosis
• By the age of 75 years, the number of uriniferous tubules is reduced to half in men.
  Japanese have the highest life expectancy limit. The average life of a Japanese woman is 8i.5 years while that of a man is 76.2 years Regeneration was discovered by Trembley in Hydra.
• When reserve food material is utilised in the body, the process is called degrowth.
• in ascidian tadpole Example larva of Herdmcmia) there occurs retrogress4e metamorphosis.
• Maximum power of autotomy (self-mutilation) is found in holothurians (echinoderms). These organisms can throw off their internal visceral organs whenever threatened by a predator. in mammals, external body parts are not regenerated.
• But mammals have a great capacity to regenerate some of the internal organs. L4er has the maximum capacity of regeneration. Similarly, if one kidney is removed, the other enlarges and takes over the function of the lost kidney. Such a reparat4e regeneration is known as compensatory hypertrophy.

NEET Biology Organisms And Population Ageing And Death Questions

Question 1. Which one of the following is (rue during ageing?

1. Decrease in blood urea and GFR
2. increase in calcium content of arteries and cartilage
3. Decrease in cholesterol content of cornea and lens
4. Decrease in calcium content of arteries and cartilage.

Answer: 2. increase in calcium content of arteries and cartilage

Population Ageing And Death NEET Biology Notes

Question 2. in human beings the growth in height becomes nearly constant after the age of:

1. 15 years
2. 20 years
3. 30 years
4. 40 years.

Answer: 2. 20 years

Question 3. Which one of the following statements is correct concerning a test tube baby?

1. Fertilization of the egg is affected outside the body; the fertilized egg is then placed in the womb of the mother where the gestation is completed
2. Fertilization of the egg and growth of the embryo arc affected in a large test tube
3. A prematurely born baby reared in an incubator
4. Fertilization of the egg is affected in the female
5. Genital tract; the fertilized egg is then taken out and grown in a large test tube.

Answer: 1. Fertilization of the egg is affected outside the body; the fertilized egg is then placed in the womb of the mother where the gestation is completed

Question 4. The science of ageing is called :

1. Chronology
2. Odontology
3. Gynaecology
4. Gerontology.

Answer: 4. Gerontology.

Question 5. Ageing in many mammals including man may be due to:

1. Adverse changes in the environment
2. interaction between hereditary factors
3. Malnutrition and stress
4. All of the above.

Answer: 4. All of the above.

Question 6.Degenerat4e changes occur during :

1. Metamorphosis only
2. Parthenogenesis
3. Ageing only
4. Both in metamorphosis and ageing.

Answer: 4. Both in metamorphosis and ageing.

Question 7. As a person becomes old, a degenerat4e process sets in the body which causes:

1. A gradual alteration in the connect4e tissue components only
2. Increases the collagen content of the connect4e tissues
3. And increases the mucopolysaccharides content of most of the connective tissue.
4. Both in metamorphosis and ageing.

Answer: 4. Both in metamorphosis and ageing.

Organisms And Population Ageing And Death NEET Question Bank

Question 8. The growth in an animal includes:

1. increase in size
2. increase in weight
3. Synthesis of new proteins
4. All.

Answer: 4. All.

Question 9. The growth rate in most of the animals is:

1. Sigmoid for all organs
2. Linear for all organs
3. Uniform for all organs
4. Different for different organs.

Answer: 4. Different for different organs.

Question 10. The pigment of ageing is:

1. Haemoglobin
2. Hacmocyanin
3. Melanin
4. Lipofuscin.

Answer: 4. Lipofuscin.

Question 11. With the advancement of age, the hair of males starts thinning due to :

1. Falling of hair
2. Low ATP formation
3. Reduced rate of protein synthesis
4. None of the above.

Answer: 3. Reduced rate of protein synthesis

Question 12. The most accepted theory of ageing is :

1. Death of brain cells
2. Non-functioning of a – cells in the pancreas
3. Less RBC in blood
4. Non-functioning of thymus gland.

Answer: 4. Non-functioning of thymus gland.

Question 13. The growth rate in childhood is controlled by :

1. Thymosine
2. Thyroxine
3. Oestrogen
4. Progesterone
5. Testosterone.

Answer: 1. Thymosine

Question 14. Which is not connected with the theory of ageing?

1. Wear and tear
2. Neurohormonal changes
3. Epimorphosis
4. Metabolic rate
5. Somatic mutation.

Answer: 3. Epimorphosis

Question 15. Growth is an irreversible process found at :

1. Subcellular growth
2. Cellular growth
3. Organ growth
4. All of the above.

Answer: 4. All of the above.

Organisms And Population Ageing And Death NEET Question Bank

Question 16. In animals, chalones are substances responsible for:

1. Regeneration
2. Ageing
3. Development
4. Parthenogenesis.

Answer: 2. Ageing

Question 17. Growth in l4ing being is called :

1. Accretion
2. intussusception
3. Aggregation
4. interaction.
5. Accumulation.

Answer: 1. Accretion

Question 18. if Hydra is broken into pieces:

1. Hydra will die
2. Hydra will undergo sexual reproduction
3. Some fragments will form a complete Hydra
4. Every fragment will grow into a complete Hydra

Answer: 4. Every fragment will grow into a complete Hydra

Question 19. Formation of the whole body from a fragment is:

1. Cpimorphosis
2. Morphallaxis
3. Epigenesis
4. Auxetic growth.

Answer: 2. Morphallaxis

Question 20. The correct sequence of growth curve for bacteria is:

1. Lag. log, stationary’ and decline
2. Lag. log, decline and stationery
3. Stationary, lag. log, decline
4. Decline, lag and log phase.

Answer: 2. Lag. log, decline and stationery

Question 21. Semilog of per minute growing bacteria is plotted against time. What will be the shape of the graph?

1. Ascending straight line
2. Sigmoid
3. Hyperbolic
4. Descending straight line.

Answer: 1. Ascending straight line

Question 22. Senescence is inhibited by :

1. Ethylene
2. Gibberellic acid
3. Cytokinin
4. Abscisic acid.

Answer: 3. Cytokinin

Question 23. In which phase proteins for spindle Fibre formation are synthesized?

1. G-phase
2. G-phase
3. S-phase
4. Anaphase.

Answer: 3. G-phase

Question 24. The maximum life span of a dog in years is :

1. 5
2. 10
3. 15
4. 20.

Answer: 4. 20

Ageing And Death In Organisms NEET Mcqs

Question 25. In the somatic cell cycle :

1. In Gjphase DNA content is double the amount of DNA present in the original cell
2. DNA replication takes place in S-phase
3. A short interphase is followed by a long mitotic
4. Phase.

Answer: 2. DNA replication takes place in S-phase

Question 26. The maximum growth rate occurs in :

1. Senescent phase
2. Stationary phase
3. Lag phase
4. Exponential phase.

Answer: 4. Exponential phase.

Question 27. Four healthy people in their twenties got involved in injuries resulting in damage and death of a few cells of the following. Which of the cells are least likely to be replaced by l4ing cells?

1. Osteocytes
2. Malpighian layer of skin
3. Liver cells
4. Neurons.

Answer: 4. Neurons.

Question 28. Based on cellular mechanisms there are two major types of regeneration found in the animals. Which of the following is the correct example of the type mentioned?

1. Morphallaxis- Regeneration of two transversely cut equal pieces of a Hydra into two small Hy draws.
2. Epimoiphosis – Replacement of old and dead erythrocytes with new ones.
3. Morphallaxis – Healing up of a wound in the skin.
4. Epimorphosis – Regeneration of crushed and filtered out pieces of a Planaria into as many new Planar- cans.

Answer: 1. Morphallaxis- Regeneration of two transversely cut equal pieces of a Hydra into two small Hy dras.

Question 29. Ageing of an animal’s body is associated with deterioration in its :

1. Connect4e tissue
2. Glandular tissue
3. Epithelial tissue
4. Both 1 and 2.

Answer: 2. Glandular tissue

Question 30. The modern idea about ageing is that our body slowly loses the power of defence against the invasion of germs and pathogens, this process starts with the
the disappearance of which organ?

1. Spleen
2. Thymus gland
3. Pituitary gland
4. Parathyroid gland.

Answer: 2. Thymus gland

Question 31. Match the items in Column I with Column II and choose the correct alternatives :

1. 1 = A 2= D, 3 = C, 4= E, 5 =B
2. 1 = B, 2 = C, 3 = D, 4 = E, 5 = A
3. 1 = B, 2 = D, 3= E, 4= C. 5 = A
4. 1 = A, 2= C, 3= B, 4 = B, 5=D
5. 1 = C, 2 = D, 3 = E, 4 = B, 5 = A

Answer: 1. 1 = A ,2= D, 3 = C, 4= E, 5 =B

Question 32. Which endocrine gland becomes inactive in old age?

1. Adrenal
2. Thyroid
3. Thymus
4. Pituitary.

Answer: 3. Thymus

Ageing And Death In Organisms NEET Mcqs

NEET Biology Organisms And Population Ageing And Death Self Assessment Test Unit Reproduction

Question 1. A low statements describing certain features of reproduction are given below :

1. Gametic fusion takes place

2. Transfer of genetic material takes place

3. Reduction division takes place

4. Progeny has some resemblance with parents Select the options that are true for both asexual and sexual reproduction from the options given blow:

1. 1 and 3
2. 2 and 3
3. 2 and 4
4. 1 and 3

Answer: 3. 2 and 4

Question 2. The term ‘clone cannot be applied to offspring formed by sexual reproduction because :

1. Offspring do not possess exact copies of parental DNA.
2. DNA of only one parent is copied and passed on to the offspring
3. Offspring are formed at different times
4. DNA of parent and offspring are completely different.

Answer: Offspring do not possess exact copies of parental DNA.

Question 3. Amoeba and Yeast reproduce asexually by fission and budding respectively, because they are :

1. Microscopic organisms
2. Heterotrophic organisms
3. Unicellular organisms
4. Uninucleate organisms

Answer:  3. Unicellular organisms

Question 4. A few statements about sexual reproduction are given below :

1. Sexual reproduction does not always require two individuals
2. Sexual reproduction generally involves gametic fusion.
3. Meiosis never occurs during sexual reproduction
4. External fertilisation is a rule during sexual reproduction.

Choose the correct statements from the options below :

1. 1 and 4
2. 1 and 2
3. 2 and 3
4. 1 and 4

Answer:  2. 1 and 2

Question 5. A multicellular, filamentous alga exhibits a type of sexual life cycle in which the meiotic division occurs after zygote formation. The adult filament of this alga has

1. Haploid vegetative cells and diploid gametangia
2. Diploid vegetative cells and diploid gametangia
3. Diploid vegetative cells and haploid gametangia
4. Haploid vegetative cells and haploid gametangia

Answer:  4. Haploid vegetative cells and haploid gametangia

Organisms And Population Ageing And Death NEET Notes

Question 6. The male gametes of rice plants have i2 chromosomes in their nucleus. The chromosome number in the female gamete, zygote and the cells of the seedling will be respectively.

1. 12, 24. 12
2. 24, 12, 12
3. 12. 24.24
4. 24, 12. 24

Answer: 3. 12. 24.24

Question 7. Given below are a few statements related to external fertilization. Choose the correct statements.

1. The male and female gametes arc formed an<i released simultaneously

2. Only a few gametes are released into the medium.

3. Water is the medium in a majority of organisms exhibiting external fertilization.

4. Offspring formed as a result of external fertilization have a better chance of survival than those formed inside an organism

1. 3 and 4
2. 1 and 3
3. 2 and 4
4. 1 and 4

Answer:  2. 1 and 3

Question 8. The statements given below describe certain features that are observed in the pistil of flowers.

1. Pistil may have many carpels

2. Each carpel may have more than one ovule

3. Each carpel has only one ovule

4. Pistil has only one carpel

Choose the statements that are true from the options below :

1. 1 and 2
2. 1 and 3
3. 2 and 4
4. 3 and 4

Answer:  1. 1 and 2

Question 9. Which of the following situations correctly describes the similarity between an angiosperm egg and a human egg?

1. Eggs of both are formed only once in a lifetime
2. Both the angiosperm egg and the human egg are stationary
3. Both the angiosperm egg and human egg are motile and transported
4. Syngamy in both results in the formation of zygote

Choose the correct answer from the options given below:

1. 2 and 4
2. 1 and 4
3. 3 and 4
4. 1 and 4

Answer:  2. 1 and 4

Question 10. The appearance of vegetat4e propagules from the nodes of plants such as sugarcane and ginger is mainly because:

1. Nodes are shorter than int models
2. Nodes have meristematic cells
3. Nodes are located near the soil
4. Nodes have non-photosynthetic cells

Answer: 2. Nodes have meristematic cells

Question 11. Which of the following statements, supports the view that elaborate sexual reproduction process appeared much later in the organic evolution?

1. Lower groups of organisms have a simpler body design

2. Asexual reproduction is common in lower groups

3. Asexual reproduction is common in higher groups of organisms

4. The high incidence of sexual reproduction in angiosperms and vertebrates.

Choose the correct answer from the options given below:

1. 1 and 2
2. 1 and 3
3. 2 and 4
4. 2 and 3

Answer: 3. 2 and 4

Organisms And Population Ageing And Death NEET Notes

Question 12. Offspring formed by sexual reproduction exhibit more variation than those formed by asexual reproduction because:

1. Sexual reproduction is a lengthy process
2. Gametes of parents have qualitat4ely different genetic composition
3. Genetic material comes from parents of two different species
4. The greater amount of DNA is involved in sexual reproduction.

Answer:  3. Gametes of parents have qualitat4ely different genetic composition

Question 13. Choose the correct statement from among the following:

1. Dioecious (hermaphrodite) organisms are seen only in animals
2. Dioccies organisms are seen only in plants
3. Dioecious organisms are seen in both plants and animals
4. Dioecious organisms are seen only in vertebrates.

Answer: 4. Dioecious organisms are seen only in vertebrates.

Question 14. There is no natural death in single-celled organisms like Amoeba and bacteria because :

1. They cannot reproduce sexually
2. They reproduce by binary fission
3. The parental body is distributed among the offspring
4. They are microscopic

Answer: 2. They reproduce by binary fission

Question 15. There are various types of reproduction. The type of reproduction adopted by an organism depends on :

1. The habitat and morphology of the organism
2. Morphology of the organism
3. Morphology and physiology of the organisms
4. The organism’s habitat, physiology and genetic makeup

Answer:  1. The habitat and morphology of the organism

Question 16. Identify the incorrect statement.

1. In asexual reproduction, the offspring produced are morphologically and genetically identical to the parent
2. Zoospores are sexual reproduct4e structures
3. In asexual reproduction, a single parent produces offspring with or without the formation of gametes
4. Conidia are asexual structures in the Penicillium

Answer: 4. Conidia are asexual structures in Penicillium

Question 17. Which of the following is a post-fertilisation event in flowering plants?

1. Transfer of pollen grains
2. Embryo development
3. Formation of flower
4. Formation of pollen grains

Answer: 4. Formation of pollen grains

Question 18. The number of chromosomes in the shoot tip cells of a maize plant is shall be :

1. 20
2. 10
3. 40
4. 15

Answer:  3. 40

Question 19. Among the terms listed below those that are not correct names for a floral whorl are :

1. Androecium
2. Carpel
3. Corolla
4. Sepal
   1. 1 and 4
   2. 3 and 4
   3. 2 and 4
   4. 1 and 3

Answer:  3. 2 and 4

Question 20. The embryo sac is to ovule as is to an anther.

1. Stamen
2. Filament
3. Pollin grain
4. Androecium

Answer: 3. Pollin grain

Question 21. In a typically complete, bisexual and hypogynous flower, the arrangements of floral whorls on the thalamus from the outermost to the innermost is.

1. Calyx, corolla, androecium and gynoccium
2. Calyx, corolla, gynoecium and Androecium
3. Gynoecium, androecium, corolla and calyx
4. Androecium, gynoecium, corolla and calyx

Answer:  1. Calyx, corolla, androecium and gynoecium

Question 22. A dicotyledonous plant bears flowers but never produces fruits and seeds. The most probable cause for the above situation is:

1. The plant is dioecious and bears only pistillate flowers
2. The plant is dioecious and bears both pistillate and staminate flowers
3. Plant is monoecious
4. The plant is dioecious and bears only staminate flowers.

Answer: 4. Plant is dioecious and bears only staminate flowers

Question 23. The outermost and innermost wall layers of microsporangium in an anther arc respectively :

1. Endothecium and tapetum
2. Epidermis and endodermis
3. The epidermis and middle layer
4. Epidermis and tapetum

Answer: 4. Epidermis and tapetum

Question 24. During microsporogenesis, meiosis occurs in :

1. Endothecium
2. Microspore mother cells
3. Microspore tetrads
4. Pollen grains

Answer:  2. Microspore mother cells

Question 25. From among the sets of terms g4en below, identify those that are associated with the gynoecium.

1. Stigma, ovule, embryo sac, placenta
2. Thalamus, pistil, style, ovule
3. Ovule, ovary, embryo sac, tapetum
4. Ovule, stamen, ovary, embryo sac

Answer: 1. Stigma, ovule, embryo sac, placenta

Question 26. Starting from the innermost part, the correct sequence of parts in an ovule is:

1. Egg, nucellus, embryo sac, integument
2. Egg, embryo sac, nucellus, integument
3. Embryo sac, nucellus, integument, egg
4. Egg, integument, embryo sac, nucellus.

Answer: 2. Egg, embryo sac, nucellus, integument

Question 27. From the statements g4en below choose the option that is true for a typical female gametophyte of a flowering plant :

1. It is 8-nucleate and 7-celled at maturity

2. It is free-nuclear during the development

3. It situated inside the integument but outside the nucellus

4. It has an egg apparatus situated at the chalazal end

1. 1 and 4
2. 2 and 3
3. 1 and 2
4. 2 and 4

Answer: 3. 1 and 2

Question 28. Autogamy can occur in a chasmogamous flower if:

1. Pollen matures before the maturity of the ovule
2. Ovules mature before the maturity of pollen
3. Both pollen and ovules mature simultaneously
4. Both anther and stigma are of equal lengths.

Answer: 3.  Both pollen and ovules mature simultaneously

Question 29. Choose the correct statement from the following :

1. Cleistogamous flowers always exhibit autogamy
2. Chasmogamous flowers always exhibit geitonogamy
3. Cleistogamous flowers exhibit both autogamy and geitonogamy
4. Chasmogamous flowers never exhibit autogamy

Answer: 1. Cleistogamous flowers always exhibit autogamy

Ageing And Death In Organisms NEET Study Material

Question 30. A particular species of plant produces light, non-sticky pollen in large numbers and its stigmas are long and feathery. These modifications facilitate pollination by:

1. Insects
2. Water
3. Wind
4. Animals

Answer: 3. Wind

Question 31. From among the situations given below, choose the one that presents both autogamy and goitnogamy.

1. Monoecious plant boating unisexual flowers
2. Dioecious plant carrying male or female  flowers
3. Monoecious plant with bisexual flowers
4. Dioecious plant with bisexual flowers

Answer:  3. Monoecious plant with bisexual flowers

Question 32. In a fertilised  Sac the haploid. diploid anti tnploul stntctutvs atv :

1. Syergid, zygote and primary endosperm nucleus
2. Synergid ,antipodal and polar nuclei
3. Amiposlal, synergid and primary endosperm nucleus
4. Synergid, polar nuclei and zygote.

Answer: 1. Syergid, zygote and primary endosperm nucleus

Question 33. In an embryo sac. the cells that degenerate after fertilisation arc :

1. Syncrgids and primary endosperm cell
2. Synergids and antipodals
3. Antipodals and primary endosperm cell
4. Egg and antipodals

Answer: 2. Synergids and antipodals

Question 34. While planning for an artificial hybridization programme involving dioecious plants, which of the following steps would not be relevant:

1. Bagging of the female flower
2. Dusting of pollen on the stigma
3. Emasculation
4. Collection of pollen

Answer:  3. Emasculation

Question 35. In the embryos of a typical dicot and a grass, true homologous structures are :

1. Coleorhiza and coleoptile
2. Coleoptile and scutellum
3. Cotyledons and scutellum
4. Hypocotyl and radicle

Answer: 2. Coleoptile and scutellum

Question 36. The phenomenon observed in some plants wherein parts of the sexual apparatus are used for forming embryos without fertilisation is called :

1. Parthenocarpy
2. Apomixis
3. Vegetat4e propagation
4. Sexual reproduction

Answer:  2. Apomixis

Question 37. In a flower, if the megaspore mother cell forms megaspores without undergoing meiosis and if one of the megaspores develops into an embryo sac, its nuclei would be :

1. Haploid
2. Diploid
3. A few haploid and a few diploid
4. With varying ploidy.

Answer: 2. Diploid

Question 38. The phenomenon wherein, the ovary develops into a fruit without fertilisation is called :

1. Parthenocarpy
2. Apomixis
3. Asexual reproduction
4. Sexual reproduction

Answer: 1. Parthenocarpy

Question 39. Choose the incorrect statement from the following :

1. In birds and mammals, internal fertilisation takes place
2. Colostrum contains antibodies and nutrients
3. Polyspermy is prevented by the chemical changes in the surface of the egg
4. In the human female implantation occurs almost seven days after fertilisation

Answer:  3. Polyspermy is prevented by the chemical changes in the surface of the egg

Question 40. Identify the wrong statement from the billowing ;

1. High levels of oestrogen trigger the ovulatory phase
2. Oogoninl cells start to proliferate and g4e rise to ova in regular cycles from puberty onwards.
3. Sperms released from seminiferous tubules arc poorly motile/non-mobile
4. Progesterone levels are high during the post-ovulatory phase of the menstrual cycle.

Answer:  2. Oogoninl cells start to proliferate and g4e rise to ova in regular cycles from puberty onwards.

Question 41. Spot the odd one out from the following structures concerning the male reproductive system :

1. Rate lists
2. Epididymis
3. Vasa efferentia
4. Isthmus

Answer: 4. Isthmus

Question 42. Seminal plasma, the fluid part of semen, is contributed by,

1. Seminal vesicle

2. Prostate

3. Urethra

4. Bulbourethral gland

1. 1 and 2
2. 1, 2 and 4
3. 2, 3 and 4
4. 1 and 4

Answer: 2. 1, 2 and 4

Question 43. Spermiation is the process of the release of sperm from:

1. Seminiferous tubules
2. Vas deferens
3. Epididymis
4. Prostate gland

Answer: 1. Seminiferous tubules

Question 44. A mature Graafian follicle is generally present in the ovary of a healthy human female around :

1. 5 – 8 days of the menstrual cycle
2. 11-17 days of menstrual cycle
3. 18-23 days of the menstrual cycle
4. 24 – 28 days of the menstrual cycle

Answer:  2. 11-17 day of menstrual cycle

Ageing And Death In Organisms NEET Study Material

Question 45. The acrosomal reaction of the sperm occurs due to :

1. Its contact with zona pellucida of the ova
2. Reactions within the uterine environment of the female
3. Reactions within the epididymal environment of the male
4. Androgens produced in the uterus

Answer: 1. Its contact with zona pellucida of the ova

Question 46. Which one of the following is not a male accessory gland?

1. Seminal vesicle
2. Ampulla
3. Prostate
4. Bulbourethral gland

Answer: 2. Ampulla

Question 47. The immature male germ cell undergoes division to produce sperm by the process of spermatogenesis. Choose the correct one concerning the above.

1. Spermatogonia have 46 chromosomes and always undergo meiotic cell division
2. Primary spermatocytes d4ide by mitotic cell d4ision
3. Secondary spermatocytes have 23 chromosomes and undergo second meiotic division
4. Spermatozoa are transformed into spermatids

Answer: 3. Secondary spermatocytes have 23 chromosomes and undergo second meiotic division

Question 48. Match between the following representing parts of the sperm and their functions and choose the correct option.

1. 1 -B  2-D 3-A   4-C
2. 1-D  2-C  3-A   4-B
3. 1-D  2-A  3-2   4-C
4. 1-B  2-A  3-C   4-D

Answer: 2. a-4 b-3 c-1 d-2

Question 49. Which among the following has 2.3 chromosomes?

1. Spermatogonia
2. Zygote
3. Secondary oOcyte
4. Ogonia

Answer: 3. Secondary oOcyte

Question 50. Match the following and choose die correct options :

1. Trophoblast 1. Embedding of blastocyst in the endometrium
2. Cleavage2. Group of cells that would differentiate as embryo
3. Inner cell mass 3. The outer layer of the blastocyst attached to the endometrium
4. Implantation 4. Mitotic d4ision of zygote Options

Answer: 2. Cleavage2. Group of cells that would differentiate as embryo

Question 51. Which of the following hormones is not secreted by the human placenta?

1. HCG
2. Estrogens
3. Progesterone
4. LH

Answer: 4. LH

Question 52. The vas deferens receives duct from the seminal vesicle and opens into the urethra as :

1. Epididymis
2. Ejaculatory duct
3. Efferent ductule
4. Ureter

Answer: 2. Enaculatory duct

Question 53. Urethral meatus refers to the following:

1. Urinogenital duct
2. Labia minora
3. Eimbriac
4. Infundibulum
5. Isthmus

Answer: 4. Infundibulum

Question 57. The method of directly injecting sperm into the ovum assisted by reproduct4e technology is called :

1. GIFT
2. ZIFT
3. ICSI
4. ET

Answer: 3. ICSI

Question 58. Increased iMR and decreased MMR in a population will:

1. Cause a rapid increase in the growth rate
2. Result in a decline in the growth rate
3. Not cause a significant change in the growth rate
4. Result in an explos4e population

Answer: 3. Not cause a significant change in growth rate

Question 59. Intensely lactating mothers do not generally conce4e due to the:

1. Suppression of gonadotropins
2. Hypersecretion of gonadotropin
3. Suppression of gametic transport
4. Suppression of fertilisation

Answer: 1. Suppression of gonadotropins

Question 60. Sterilisation techniques are generally foolproof methods of contraception with least side effects. Yet, this is the last option for the couples because :

1. It is almost irreversible

2. Of the misconception that it will reduce sexual urge/ dr4e

3. It is a surgical procedure

4. Of lack of sufficient facilities in many parts of the country

Choose the correct option :

1. 1 and 3
2. 2 and 3
3. 2 and 4
4. 1, 2, 3 and 4

Answer: 4. 1, 2, 3 and 4

NEET Biology Plant Growth and Development Basic Features Of Development

• Growth: It is a biological phenomenon involving an increase in the quantity of metabolically active protoplasm, accompanied by an increase in cell number cell size or both.
• Reproduction: The process of producing the young ones of one’s type is called reproduction.
• Development: It is the development of a small, simple one-celled zygote into a large complex-celled adult plant or animal.
• Embryonic or Pre-natal period: It is the period of development of an animal from fertilization to the hatching or birth stage.
• Post-embryonic or Post-natal period: It is the period of changes or transformations which occur in an animal from hatching or birth up to death.
• Ontogeny: The total of events and progressive changes which transform a fertilized egg into a mature individual capable of reproducing is known as ontogeny.
• Reproductive unit: It is is unit produced from either one parent or two parents which undergo a series of developmental changes to give rise to the body of offspring which resembles the parent.
• Gamete: It is the structure produced by the male or female individual through meiosis (gametogenesis) in the sex organs, which takes part in fertilization to form a zygote.
• Zygote: It is the sexual fusion product of male and female gametes.
• Embryo: It is the stage of life history between fertilization and the hatching or birth of a young one. It is derived from the fertilized egg or zygote. The embryo is diploid. It is formed as a result of fertilization and subsequent changes.
• Blastogenesis: The process of development of the progenies from reproductive units such as fragments and buds is called blastogenesis. The process is common in those individuals who are produced by asexual reproduction.
• Embryogenesis: The process of development of the embryo from the zygote produced by the fusion of male and female gametes in sexual reproduction is called embryogenesis. This process occurs in individuals who reproduce by sexual reproduction.

Read and Learn More NEET Biology Notes

• Gametogenesis: The production and differentiation of male and female haploid gametes from gonads.
• Fertilization: The union or syngamy of haploid nuclei of male and female gametes to form a diploid zygote is called fertilization.
• Cleavage and Blastula: A series of repeated mitotic divisions of an egg that form a cluster of balls of cells (blastomeres) is called blastula.
• Gastrulation: The morphogenetic movements of cells of the blastula to give rise to germinal layers, ectoderm, endoderm and mesoderm is called gastrulation. The embryo thus formed with archenteron is called gastrula.
• Growth: Growth is a permanent increase in the synthesis of new nuclear material and cytoplasm.
• Differentiation: It refers to events by which parts become different from one another. It may be morphological, chemical, behavioural, or differentiation.
• Spermatogenesis: The process of formation of sperms from the sperm mother cell of the testis. It involves the following phases:

Plant Growth And Development NEET Notes

Multiplication phase: The sperms are formed from the sperm mother cells, present in the germinal layer of seminiferous tubules of the testis. Some of the mother cells enlarge and divide mitotically to form spermatogonia.

1. Growth phase: Some of them enter a period of growth and are called primary spermatocytes which are diploid.
2. Maturation phase: These cells divide meiotically to form two haploid, secondary spermatocytes. Each secondary spermatocyte again divides. Thus one primary spermatocyte forms four haploid spermatids.

• Spermiogenesis (Spermateliosis): The process of conversion of spermatid into motile spermatozoa is called spermiogenesis.
• It involves movements of cell organelles characteristics of mature sperm such as shrinking of nucleus forming the head, Golgi complex gathering in front of nucleus forming acrosome, change in centriole as distal centriole from the axial filament, mitochondria form spiral sheath and middle piece.
• All these changes are aimed at keeping the spermatozoa small, light and motile. Oogenesis. The process of formation of the ovum from the ovum mother cells of the ovary. It is similar to spermatogenesis and completed in three phases viz. multiplicative phase, growth phase and maturation phase.

Similarities between Spermatogenesis and Oogenesis:

1. Both processes start with primordial germ cells derived from the germinal epithelium of gonads and occur inside the gonad.
2. Both the processes are completed in three phases i.e. multiplication, growth and maturation and show meiosis in the maturation phase.
3. Both processes produce haploid gametes.

Difference Between Spermatogenesis and Oogenesis:

NEET Biology Plant Growth and Development Structure Of Ovum

In all the animals, ova arc single-celled. The ovum is surrounded by a primary membrane called vitelline membrane which is produced after the release from the ovary, the secondary and tertiary membranes are secreted by the Graafian follicle or lining of the oviduct. These layers may be albuminous as in amphibians or may be porous, calcareous as in birds.

• Most animal eggs are spherical or oval, non-motile but on close examination it is noted that one pole is different from the other. The pole from which polar bodies are given off is called the animal pole while the opposite is termed as vegetal pole.
• Thus it is said to have polarity. Thus various cytoplasmic substances are unequally distributed along the axis. The nucleus, also called a germinal vesicle having a chromatin network is bounded by a nuclear membrane.
• It also contains prominent nucleolus. All animal eggs contain some reserve material to provide food called yolk. The cytoplasm of the ovum is called ooplasm. It lacks a centrosome but contains cortical granules derived from Golgi bodies in its peripheral region termed as cortex.

NEET Biology Plant Growth and Development Functions Of Ovum

1. It contributes female’s haploid set of chromosomes.
2. After fertilization, forms a zygote which gives rise to young animals by development.
3. Egg Membranes Protect The Developing Embryo.
4. The eggs are of different sizes. The smallest egg is that of the mouse (0.075 mm) find the largest is that of the ostrich bird (175 mm).

NEET Biology Plant Growth and Development Types Of Eggs

1. Types of eggs based on amount or yolk.

1. Alecvithal cups. Yolk absent c.g. Mctathcrian and cutlierian mammals.
2. Leithal eggs. Eggs contain yolk. They are of three types.
   1. Microlcoithal or olipolceithul Eggs: Microlcoithal Eggs contain very small amounts of yolk
      • Examples: Hydra, and sea urchin. Amphioxus, Tunicatcs.
   2. Mesolccithal Eggs: Mesolccithal Eggs contain a moderate amount of yolk
      • Examples: Earthworm, Dipnoi fishes, and amphibians.
   3. Macrolecithal or mepalecithal or polylccithal eggs: Macrolecithal Eggs contain large quantities of yolk
      • Examples: birds, fishes, reptiles, prototherian mammals and insects.

2. According to the distribution of yolk:

Eggs are of the following types

1. Home-lethal or Isolecithal eggs have evenly distributed yolk
   • Example: Porifers, Amphioxus, Echinodemiates.
2. Heterolecithal Or Anisolecithal Eggs:  Have Localized Yolk.
   • They Are Of The Following Types
     1. Telolecithal eggs: Telolecithal eggs in amphibians— yolk concentrated towards one side.
     2. Meiolecithal eggs: Meiolecithal eggs of birds and reptiles are large and yolk occupies the entire ooplasm.
     3. Centrolecithal eggs: Centrolecithal eggs in insects have yolk in the centre with cytoplasm forming a thin layer around.

3. Types Of Eggs According To Covering:

1. Cleidoic eggs. These eggs are fully laden with yolk and surrounded by albumen and water-proof shells made up of calcium
   • Example: Eggs of reptiles and birds.
2. Non-cleidoic eggs: Non-cleidoic eggs In such a shell is absent.

4. Types Of Eggs According To The Type Of Development:

1. Determinate or mosaic eggs. In such eggs, cleavage is of a determinate type and each part of the egg has a definite fate
   • Examples: Porifers, Platyhelminthes, annelids, arthropods and molluscs.
2. Indeterminate or regulative eggs. In this type, each early blastomere on separation from others may give rise to a complete embryo
   • Example: echinoderms and chordates.

Phases Of Plant Growth NEET Biology

NEET Biology Plant Growth and Development Egg Membranes Or Coats

Eggs possess unique coats beside the plasma membranes. They safeguard the eggs from predators and physical harm while supplying nourishment.

1. The primary membrane secreted by the egg is the vitelline membrane.
2. The secondary membrane is constituted by follicular cells of the ovary that encase the ovum. Chorion in the egg of Herdmania and zona pellucida in the mammalian egg.
3. Tertiary membrane produced by the oviduct’s gland. Jelly-like coating around the eggs of fish and amphibians, together with albumen, shell membranes, and the shell encasing the eggs of reptiles and birds.

NEET Biology Plant Growth and Development Structure Of Mammalian Sperm

Structure. A mammalian sperm is a minute, microscopic, flagellated and motile gamete with no nutritive material, protective envelopes and most cell organelles like ribosome, endoplasmic reticulum, etc. It is formed of four parts, each performing a specific function:

1. Head: The shape of the head varies in different mammals. It is generally oval and flat (in man, bull, rabbit). The head is formed of two parts :

• Acrosome (Gr. Akron = extremity; soma = body):  It is a small pointed structure present at the tip of the nucleus. It is formed from a part of the Golgi body of the spermatid. During the sperm entry, the acrosome secretes a lytic enzyme called hyaluronidase which helps in the penetration of the ovum.
• Nucleus: It is generally long, narrow and pointed but is flat and oval in human sperm. It is formed by condensation of nuclear chromatin of spermatid and loss of RNA, nucleolus and acidic proteins. Chemically, the nucleus is formed of deoxyribonucleoprotein (DNA + basic proteins). It is the carrier of genetic information.

The acrosome and anterior half of the nucleus are covered by a fibrillar sheath galea.

 2. Neck: It is the smallest part of spermatozoan and may be indistinct. It is formed of two centrioles perpendicular to each other and is formed from the centrosome of the spermatid.

• Each centriole is a microtubular triplet structure having a 9 + 0 arrangement. The proximal centriole lies in a depression in the posterior surface of the nucleus and is perpendicular to the main axis of the sperm. The distal centriole is along the longitudinal axis of the sperm.
• Centrioles form a spindle for the first cleavage of the zygote. Distal centriole acts as a basal body and gives rise to the axoneme of the sperm tail.

 3. Middle piece: It lies behind the neck and is cylindrical in human sperm.

• It is formed of a mitochondrial spiral called nebenkern around the proximal part of the axoneme.
• The middle piece is a powerhouse of sperm.
• The posterior half of the nucleus neck and middle piece of sperm is covered by a sheath called a manchette.
• Tail (Flagellum) It is the longest part of sperm. It is slender and tapering.

It comprises two parts: Central contractile and microtubular, axoneme or axial filament, and outer protoplasmic sheath.

• Axoneme is formed of 11 proteinous microtubules arranged in a 9 + 2 manner.
• Sometimes, a ring centriole may be present at the junction of the middle piece and flagellum.
• The tail shows lashing movements which provide a forward push to the sperm.

 4. Viability: It is the period up to which the sperm can fertilize an ovum. The viability of human sperm is about 24 hours.

NEET Biology Plant Growth and Development Fertilization

Fertilization. It is a fitness by which male and female gametes come close and fuse to form a zygote. The union of two gametes is termed syngamy and the intermixing of nuclei is amphimixis.

Steps Involved in fertilization are :

1. Encounter of spermatozoa and ova: It may occur inside the body (internal fertilization) or outside the body(external fertilization).
2. Capacitation and contact. Sperm (antifertilizin) and ovum (fertilizin) show fertilizin- antifertilizin reaction which is highly specific for a species.
3. Acrosome reaction and penetration: Golgi bodies of acrosome secrete enzymes.
   hyaluronidase which dissolves the membranes of the ovum so that materials of sperm can penetrate.
4. Activation of ovum: Immediately after the apical tip of the acrosomal tubule touches the egg plasma membrane, a fusion of both membranes takes place and a single continuous mosaic membrane is formed.

Thus plasma membrane of both gametes becomes continuous and forms a zygote. At this time certain changes occur in the cytoplasm of the egg which are collectively termed as activation of the ovum. It includes the following events.

1. Fertilization cone formation: Coming in contact with the acrosomal filament of spermatozoan, the cytoplasm of the egg bulges forward to produce a conical projection, the fertilization cone. It gradually engulfs the spermatozoan.
2. Cortical reactions and fertilization membrane formation: It may differ from one group of animals to the other, but, in most groups, it fundamentally culminates into the formation of a membrane, called fertilization membrane, outside the egg plasma membrane. This membrane blocks the entrance of late-arriving spermatozoa.
3. Metabolic activation: Following metabolic changes occur in the egg at the time of fertilization.
4. Changes in the plasma membrane: The permeability of the egg plasma membrane increases for the molecules of water, glycol and ions of K+, P04-3 etc. Its electrical potential becomes more positive in the beginning but more negative later on.
5. Ionic changes: The concentration of cations such as Na+, Ca++ and K+ changes during fertilization.
6. Changes in coenzyme: During fertilization, the inactive enzyme NAD-kinase becomes active and changes NAD into NADP and NADPH by phosphorylation.
7. Respiratory changes: Fertilization increases the rate of respiration in those eggs in which maturation is completed before fertilization (e.g., sea urchin) and decreases in those eggs in which fertilization occurs at the first maturation division (e.g., Chaetopterus).The respiratory rate increases for the release of more ATP.
8. Change in the rate of protein synthesis: During fertilization, the inhibitor enzymes are removed to initiate an action of protein synthesis.
9. Initiation of mitosis: It takes place due to the following agencies :

Immediately after fertilization, the rate of DNA synthesis increases many- folds and so also the uptake of cytoplasmic DNA Polymerase enzyme, which is required in the biosynthesis of DNA. The sperm introduces its centriole and by contributing a second centriole it initiates the formation of a spindle.

Plant Growth Regulators NEET Study Material

• Migration of pronucleus and amphimixis: To perform the act of amphimixis, the sperm nucleus has to perform two activities i.e., it has to become pronuclei and to migrate v from the site of penetration to the site of amphimixis. The fusion of male and female pronuclei is termed amphimixis.
  • Significance Of Fertilization:

1. 1. 1. It stimulates the egg to complete its maturation.
      2. The fusion of male and female pronuclei in fertilization restores the diploid number of chromosomes and activation of secondary oocytes results in a mature form of ovum. The ovum which is in a quiescent state with a low metabolic rate restores its normal metabolic activity.
      3. Fertilization initiates cleavage or segregation.
      4. The combination of the chromatin material from two different parents forms the physical basis of biparental inheritance and variation.
      5. The centriole of sperm initiates the first division of zygote timelines and further entry of sperm is checked by the fertility/action membrane.

Ovipary, Vivipnry and Ovovivipnry:

• Osipary: It is the development of an embryo inside its egg delivered outside the body. The fertilization may be external or internal.
• Vivipnry: It is the development of an embryo inside the uterus of a female connected using the placenta. The fertilization is internal. The female gives birth to the young one.
• Ovovivipnry: The phenomenon of retaining eggs and the development of embryos in the body till birth without forming any organic connection for obtaining extra nourishment i.e. no placenta formation. Fertilization is internal.

NEET Biology Plant Growth and DevelopmentCleavage

Cleavage: The series of divisions that occur inside the fertilized egg or zygote to transform it into a multicellular body called blastula is called cleavage. They produce blastomeres.

Characteristics of Cleavage:

1. Cleavage divisions are mitotic and occur one after the other. However, the rate depends upon species, amount of yolk and temperature.
2. During cleavage, growth does not take place and the size and volume of the embryo remain the same and the size of blastomeres is reduced.
3. The nuclear and cytoplasmic ratio becomes very low for the zygote and as a result cleavage increases.
4. During cleavage general shape of the embryo does not change.
5. All blastomeres divide simultaneously during early cleavage.
6. For rapid nuclear division, there is a great increase in the synthesis of DNA.
7. O2 consumption increases during cleavage.

The cleavage division differs from ordinary mitotic division in the following ways :

1. The cleavage division is not followed by the growth of daughter cells before they divide but during ordinary mitotic division, each division is followed by a growth of daughter cells before the next division starts.
2. The rate of cleavage depends in different species on temperature but during mitosis, it is not so.
3. During cleavage nuclear and cytoplasmic ratio is changed.
4. During cleavage, the blastomeres divide simultaneously but in ordinary mitosis all the daughter cells divide approximately at the same time.
5. The cleavage differs from ordinary mitosis of large-sized zygotes, and it is meant basically to reduce the size of blastomeres.

Pattern of Cleavage: Three common patterns of cleavage are radial, bilateral and spiral cleavage.

1. Radial cleavage: In radial cleavage, the successive cleavage planes cutting straight through the egg are at a right angle to one another. The resultant blastomeres become symmetrically, exposed around the animal-vegetal axis. Such type of cleavage occurs in sponges, coelenterates and a few molluscs.
2. Bilateral cleavage: In this pattern of cleavage, the blastomeres are so arranged that the right and left sides become apparent, e.g., Cephalopods, a few Echinoderms and Vertebrates.
3. Spiral cleavage:  In this pattern of cleavage, the furrows are so formed that the blastomeres are arranged in a spiral manner around the animal-vegetal axis e.g., Flatworms, annelids and molluscs.

Planes Of Cleavage During cleavage, different cleavage furrows may divide the egg into different planes.

1. Meridional plane. Cleavage furrow passes through the centre of the animal-vegetal axis and bisects both the poles of the egg. e.g., Frog.
2. Vertical plane. Cleavage furrow passes in a direction from the animal pole towards the vegetal pole. For. first cleavage furrows of Amin calva and chick.
3. Equatorial plane. It bisects the egg at right angles to the main axis and halfway between the animal and vegetal poles, e.g…… first cleavage plane of eggs of higher mammals.
4. Latitudinal plane. It is similar to equatorial, but it courses through the cytoplasm on either side of the equatorial plane, e.g., the third cleavage planes of Amphioxus and frog.

Auxins And Their Role In Plant Development NEET

Types of cleavage: The amount and pattern of distribution of yolk determine the type of cleavage. It is of the following types :

• Holoblastic cleavage: In alecithal, isolecithal and slightly telolecithal eggs, the zygote and the blastomeres divide completely. It results in a cocloblastula i.e., a blastula with a central cavity called the blastocoel. Holoblastic cleavage is of two types
• Equal holoblastic cleavage: The cleavage produces approximately equal-sized blastomeres throughout. It occurs in alecithal eggs of rabbits and microlecithal eggs of sea squirts, amphioxus, marsupials and other placental mammals.

• Unequal holoblastic cleavage: This cleavage in later divisions gives rise to unequal blastomeres, small micromeres and large megameres. It occurs in telolecithal eggs of bony fishes and amphibians.
• Meroblastic Cleavage: In this type of cleavage, division occurs only in the small amount of metabolically active cytoplasm. The yolk remains undivided. It is found in macrolecithal eggs. It is of two types :
• Discoidal Cleavage: It is confined to the active cytoplasm located at the animal pole and occurs in isolecithal eggs of reptiles, birds and egg-laying mammals. It results in a blastula called a disco blastula.
• Superficial Cleavage: It occurs in the centrolecithal eggs of insects. The nucleus placed in the centre of the yolk divides repeatedly to form many daughter nuclei which migrate to the peripheral yolk-free cytoplasm. It then cleaves into many uninucleate blastomeres arranged around the yolk. It results in a superficial blastula consisting of single-layered epithelium enclosing yolk instead of blastocoel.

Significance of cleavage:

1. It produces a large number of cells from a single-celled zygote by repeated divisions and results in the formation of the embryo. , .•
2. It prepares the embryo for the migration of cells to their fixed position during gastrulation.
3. Preparation and initiation of the process of cell differentiation.

NEET Biology Plant Growth and Development Gastrulation

Gastrulation. It is a phase of embryonic development during which cell movements establish the three primary germinal layers and initiate morphogenesis.

The most important features of gastrulation in all animals are :

1. Complex but orderly and irreversible morphogenetic movements involving large masses.
2. The rhythm of cellular division is slowed down.
3. Growth if any is insignificant.
4. The nuclei become more active.
5. Formation of archenteron surrounded by endoderm.
6. The type of metabolism changes and the rate of oxidation is intensified.
7. Chemodifferentiation starts with the synthesis of new proteins.

• Epiboly: It involves stretching and spreading movements of ectoderm-forming cells to surround the embryo except at one pole called the blastopore.
• Emboly: It is the shifting or migration of the cells in such a way as to form internal layers of the mesoderm and endoderm of the embryo. It can occur by five methods.

1. 1. Invagination: It is the simplest type of emboly. In this method, the vegetal pole side of the blastula simply caves in or pushes into the interior e.g. Amphioxus and Invertebrates.
   2. Involution: It is the active rolling in of the endodermal and mesodermal cells from the surface to the interior through blastopore e.g., Frog.
   3. Ingression:  It is the proliferation of cells from the inner surface of the blastoderm into blastocoel which gets filled up with new cells and results in the formation of solid gastrula. The archenteron appears later on by splitting up of internal mass of cells. It may be unipolar as in Obelia or apolar as in Hydra.
   4. Delamination: Separation of sheets of cells to form two layers called epiblast and hypoblast e.g. chick, mammals.
   5. Convergence: It involves the migration of blastomeres from the outer surface towards the blastoporal lips.

NEET Biology Plant Growth and Development Fate Of There Germinallayers

Germinal layers:

Ectoderm, Mesoderm and Endoderm are the three primary germinal layers of the embryo as all the organs differentiate and develop from these layers.

NEET Biology Plant Growth and Development Morphogenesis And Nieekrentlation

Every living organism starts its life from a one-celled structure, a zygote, formed by a union of male and female gametes. From this one-celled stage, a multicellular stage is established by groups of processes of which morphogenesis and differentiation are outstanding.

Morphogenesis: It involves the formation of various structures in an individual organism resulting in the establishment of a young one.

There are two main processes of morphogenesis, namely growth and form:

1. Growth: Molecular growth increases the size of the individual cell. The mitotic division of cells, the most significant process of growth involves the increase in the number of cells and eventually the increase in bulk and complexity of the organism.
2. Form: The growth leads to the form of an individual plant or animal. The resultant of growth establishes various structures and organs. When a structure or an organ has reached its maximum limitation of size, further growth stops. The form is determined by polarity and symmetry. Polarity is of the three dimensions. In an organism one exerts dominance.

The head exerts dominance over the rest of the body. Due to polarity, there is a differentiation of anterior, posterior, right and left sides. Symmetry is the regularity of the arrangement of parts in an organism.

Differentiation: This involves the operational and functional components of development. The zygote divides repeatedly finally establishing millions of cells all having the same types of genes. Yet these cells differentiate into various organs. A group of cells at an early stage maintain certain functions while in the later part of life take up different functions.

Up to a stage the cells are capable of giving rise to any structure i.e. totipotent and after a time when a cell produces special types of cells, there cannot be any further transformation of the cell. The final stage reaches specialisation so that the cell is set apart to perform a definite function.

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Cell differentiation may come about in three methods :

1. The developing differences among cells might be the result of progressive changes in gene action. Further, gene activity patterns might change differently in different cells resulting in differentiation.
2. While the gene action might remain constant, the cytoplasmic operations may become progressively altered.
3. Nuclear and cytoplasmic changes might occur reciprocally.
4. The differentiation may start from the molecular level leading to cellular differentiation.

NEET Biology Plant Growth and Development Formation Of Three Germinal Layers In Mammal

Development of three germinal layers. In viviparous mammals, fertilization occurs internally.

The subsequent processes transpire during the creation of the three germinal layers:

1. Cleavage:

The zygote undergoes holoblastic cleavage in the fallopian canal.

2. Morula:

A compact sphere of cells is generated through successive cleavage divisions.

3. Blastula:

(Blastodermic vesicle or Blastocyst) A chamber known as the blastocoel emerges in the developing embryo. The blastodermic vesicle is encased by an external cellular layer known as the trophoectoderm. The blastodermic vesicle exhibits an interior aggregation of cells resulting from differentiation. This aggregation of cells is referred to as the inner cell mass.

4. Gastrulation:

At this stage, the morphogenetic movements of the cells, such as epiboly and emboly, occur in small aggregates or sheets.

Consequently, three germinal layers are established:

1. Endoderm
2. Mesoderm
3. Ectoderm

1. Development of Endoderm:

Certain cells from the inner cell mass undergo delamination.

• Cells migrate in layers or aggregates within the blastocoel. These represent the prospective endodermal cells.
• These cells organize themselves as the second layer, situated between the inner and outer layers of the blastodermic vesicle.
• The blastocoel vanishes, and a new hollow emerges. The newly formed cavity is referred to as the archenteron.
• The residual mass of embryonal knob cells becomes convoluted and systematically organized to create an embryonic disc.

2. Formation or mesoderm:

The cells at the caudal end of the embryonic disc initiate proliferation and subsequently detach from the disc to produce mesoderm.

3. Development of ectoderm:

 Following the detachment of mesodermal cells from the embryonic disc, the remaining cells in the disc organize into a separate layer, forming the ectoderm.

NEET Biology Plant Growth and Development Placenta

• Placenta: A vascular organ that unites the foetus to the wall of the uterus in all mammals except marsupials and monotremes is called the placenta and its formation is plantation.
• Structure or Kpithelio-shoring placenta: Epitheliochorial is the simple and basic type of placenta formed in marsupials, pigs, horses, etc. In this case, some of the components are derived from the uterine wall of the mother while the other parts are derived from the foetus itself.

1. 1. Maternal components are (a) mucous membranes of the uterine wall (b) uterine connective tissue (maternal mesenchyme) (c) endothelium of maternal blood capillaries.
   2. Foetal components are A wall of foetal blood capillaries and foetal connective tissue. Foetal chorionic epithelium.
   3. Functions of the placenta:  The placenta serves primarily as an organ that permits the interchange of material earned in the blood of the mother and foetus. The main functions are :
   4. Nutrition: Supply of nutrient materials to the foetus. Respiration. Supply of 02 to the foetus and receive C02 back from it. Excretion. Fluid nitrogenous waste products escape through the placenta. Barrier. The placenta is a barrier-like semipermeable membrane.
   5. Storage: The placenta stores fat, glycogen and iron for the embryo before die formation of the liver. Hormonal function. The placenta secretes extra-ovarian hormones estrogen and progesterone in females during pregnancy that serve to maintain the foetus.

Classification of the placenta: The placenta is of five types depending upon the number of tissue layers that separate the foetal blood from maternal blood.

Epitheliochorial placenta (all six layers) e.g. horse, pig and donkeySyndesmochorial placenta (five layers present, uterine epithelium eroded e.g., cow, goat, sheep Endotheliochorial placenta (four layers present-uterine epithelium and connective tissue eroded) e.g. dog and catHaemochorial placenta (three layers present-material three layers eroded) e.g, primates including human andHaemoendothelial placenta (all the maternal and two foetal tissue layers eroded) e.g. rodents and rabbits.

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Types of placentae according to the distribution of villi on chorion.

1. Diffuse placenta: Chorionic villi remain scattered all over the surface of the chorion e.g., pig, horse, lemur.
2. Cotyledonary placenta: The villi are found in groups or patches e.g. cattle, sheep, deer
3. Zonary placenta: The villi are developed in the form of a belt or girdle e.g. cats, dogs Discoidal placenta. The villi continue developing only on one side e.g. mouse, rat, human, monkey.
4. The placenta is of three types, viz. Allantoic, yolk sac and chorionic placenta: about the foetal membrane that takes part in its formation.

NEET Biology Plant Growth and Development Vitellogenesis

The synthesis of yolk is termed vitellogenesis. Recent investigations have revealed that yolk is not necessarily synthesized in oocytes but produced elsewhere in some extra ovarian tissue such as fat bodies in insects.

• In fishes, amphibians and also in gastropod molluscs, its synthesis takes place inside modified mitochondria.
• In other vertebrates, yolk is produced in liver cells. It is transported to the ovarian follicle by blood in the soluble form. From these cells of the follicle, the oocyte takes the yolk by pinocytosis.
• The Golgi complex and endoplasmic reticulum of oocytes transfer these yolk components to modified mitochondria and convert them into insoluble forms.

1. 1. Composition of yolk: The yolk is the reserve food material in the egg. It is composed of proteins, phospholipids and neutral fats. The yolk may be a protein yolk if it contains mainly protein. If the yolk consists mainly of phospholipids, neutral fats and small fats, it is termed a fatty yolk. Both kinds of yolk are present side by side in the eggs but protein yolk is the main constituent of many invertebrates and chordates.
   2. Utilization of yolk: In the isolecithal eggs Example: frog) the yolk gets distributed to all the daughter cells at the time of cleavage. However, at later stages, some cells may have more yolk due to unequal division. The yolk is broken down into simpler substances and utilized in the synthesis of new protoplasmic constituents.

In the acrolectal egg of birds, the yolk is absorbed by diffusion in the early stages. Later on, a yolk sac develops around the yolk mass from mesoderm and endoderm. Blood vessels called vitelline arteries and veins connect the yolk sac with the heart. The enzymes from the yolk sac digest the yolk into soluble form, which is then taken to the heart and vitelline veins and then distributed to all parts of the developing embryo.

NEET Biology Plant Growth and Development Hereditary Defects

• Teratology: It is the branch of developmental biology which deals with the study of abnormal development during embryogenesis. The ways and means by which abnormal developments occur during embryogenesis are called teratogenesis.
• List of hereditary defects, Colour blindness harelip (Cleft plate Clubfoot Hole in the heartAbsence of hands, feet, arms or legs (Meromelia) Right half body normal and left like dwarf (Achondroplasia) Mongolism Phenylketonuria Albinism Alkaptonuria Haemophilia Polydactyly Cat cry syndrome (at) Turner’s syndrome and Klinefelter syndrome.
• Identical twins: The twins are of the same sex and are identical in all respects including appearance, size and behaviour.
  The identical twins are monozygotic because they develop as a result of fertilization of the single ovum by a single sperm but the zygote divides into two halves and each half gives rise to a child. Each gets attached to the same placenta.
• Fraternal twins: The fraternal twins are dizygotic as they are produced due to the fertilization of two different eggs. They may or may not belong to the same sex. They may or may not resemble each other.
• Normally the ovaries release a single egg at a time or if two eggs are released both may be fertilized and then may develop into two separate individuals, thus fraternal twins develop from two different zygotes, hence termed dizygotic twins. They are connected to the uterine wall by a separate placenta.
• Conjoined twins: Twins are generally normal babies, but some twins may be abnormal in shape, structure or development. Some twins may be fused wholly or in part, such fused twins are called conjoined twins. The degree of union may be slight or extensive. Union is by heads and upper trunk.

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NEET Biology Plant Growth and Development Important Notes

1. Spermiogenesis: The process of conversion of a spermatid into a functional spermatozoan by the process of differentiation of specialization is called spermiogenesis or spermioteliosis.
2. Sertoli cells: These are indifferent cells situated in the lining of seminiferous tubules which provide nourishment to the differentiating spermatozoa. Sperms’s head is kept embedded in Sertoli cells for this purpose.
3. External fertilization: The fusion of male and female gametes takes place outside the body of a female animal.
4. Internal fertilization: The fusion of male and female gametes takes place inside the body of a female animal.
5. Amnion: A thin extra-embryonic membrane forms a closed sac around the embryo in birds, reptiles and mammals.
6. Amniota: A collective term for the reptiles, birds and mammals, all of which have an amnion.
7. Anamniote: Any animal of which the amnion is absent during embryonic development.
8. Amniotic fluid: A substance that fills the amnion to protect the embryo from shock and industry.
9. Amniocentesis: A procedure during pregnancy by which the abdominal wall and foetal membrane are punctured with a cannula to withdraw amniotic fluid.
10. Amphimixis: The union of nuclei of egg and sperm in sexual reproduction.
11. Allantois: A fluid-filled, sac-like extraembryonic membrane lying between the chorion and amnion of reptiles, birds and mammals.
12. Allantochorion: The extraembryonic membrane is formed by the fusion of the outer wall of allantois and with the primitive chorion.
13. Chemo-difTerentiation: It is the chemical differentiation of cells of the embryo during development.
14. Cyto-differences: It is the differentiation of cells ol ciuluyo dining development.
15. no-dinViviilintlon: It location of the tissue mill also ballots ns histogenesis.
16. Orgnn-dinVivntlntlon: It is tot million of guns limit the embryo.
17. Kmhnoule Murillo: The supply of required materials which are essential for the synthesis of unit ami and other compounds ami for the production of energy during the development of the embryo is called embryonic nutrition. The materials required are amino acids, minerals and oxygen.
18. Diapause: The sexual rest period in insects is called diapause.
19. Kmlometrium: Glandular mucous membrane lining of the uterus.
20. Genome: The set of all different chromosomes found in each nucleus of a given species. A haploid nucleus has one genome.
21. Germinal vesicle: Nucleus of the animal oocyte during the period of cytoplasmic growth.
22. Gestation period: Length of time from conception to birth in viviparous animals.
23. lactation: Production of milk.
24. Monoccious:fUiscxual or hermaphrodite).
25. Mullerian Duct: Oviduct of female gnathostome vertebrate.
26. Neoteny: Persistence of the form of a larva or any other stage (larva becomes sexually matured.)
    • Example: Axolotl Larva of Salamander in Amphibians
27. Nidicolous birds: Those which hatch undeveloped.
28. Nymph: Young states of exopterygote insect.
29. Oxytocin: A hormone secreted by the posterior lobe of the pituitary gland which causes labour pains (contraction of uterine muscles.).
30. Secondary sexual characters: A characteristic of animals which differ between the two sexes.
31. Seminal vesicles: Organs which store sperm in males (cf).
32. Spermatheca. Organs which store sperm in female ($).
33. Syngamy:Union of gametes is termed syngamy.
34. Testosterone: A principal male hormone.
35. Urethra: Duct leading from the urinary bladder of mammals to the exterior.
36. Uterus masculinus: A sac-like structure dorsal to the bladder in male mammals.
37. Vitelline membrane:  Primary egg membrane secreted by the egg.
38. Yolk plugs: A mass of macromeres which closes the blastopore in the developing embryo

• Colostrum. The first milk which comes out from the mother’s mammary glands just after childbirth is known as colostrum. It is rich in calories and proteins. It contains antibodies.
• On average human ejaculate of 3 – 4 ml of semen contains 80-100 million spermatozoa.
• Virus infection of the mother e.g. by the rubella (German measles) virus or exposure to certain chemicals may cause malformation in the developing embryo. Such agents are called teratogens.  All the systems in a developing foetus are formed by the three months of pregnancy.
• cv During further development after three months, there was growth and a few minor structural modifications. Extra-embryonic membranes include the yolk sac, amnion, chorion and allantois.
• Yolk sac is also found in like certain fishes Example: Scoliodon), bony fishes and a few amphibians
• Example: Necturus having an egg.
• Amnion, chorion and allantois are formed only in am- niote embryos as their development occurs on land either inside the egg or in the uterus of the mother.
• These are not formed in amniotes as their development occurs in water so there is no problem of desiccation, supply of oxygen and removal of wastes. c& Amnion is an innermost embryonic membrane and never participates in placenta formation.
• c& Chorion is an outermost embryonic membrane and always participates in placenta formation.
• Polarity. The existence of a definite axis in the egg and the embryo is called polarity. In the egg, polarity is indicated by the position of the nucleus and the yolk.
• Inducers (Organizers). The cells that induce or control die developmental fate of the neighbouring cells in an embryo are called inducers or organizers.
  c& Inductors. These are the chemicals which the inducers release to guide the fate of the adjacent cells.

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• Identical twins:  Twins are the term used to describe the delivery of two or more infants in a single birth. These may be identical twins, monozygotic twins, fraternal, dizygotic, or non-identical twins.
• Siamese siblings: Conjoined twins are joined at the pelvis, chest, kick, and face. These are monozygotic and have been surgically separated for the first time in Siam.
• In the process of frog oogenesis, a single oogonium generates a single ovum and only two polar bodies.
• In mammals, a fertilization membrane is not formed; however, die enzymes that are released following the formation of the zona pellucid neutralize sperm receptors, preventing any additional sperm from binding to them.
• Transformation: Metamorphosis is the term used to describe the process by which a juvenile individual undergoes a transformation into a morphologically and physiologically distinct adult. There are two varieties of it.
• Metamorphosis that is retrogressive: The transformation of an advanced larva into a degenerate adult, such as Merdmania. Sacculina.
• Metamorphosis in progress: When a simplified larva transitions into an advanced adult, such as a frog.
• Martinis are complimentary: A male and a female heifer that were sexually underdeveloped were united.
• Fate diagram: Diagram illustrating presumptive or potential regions on the blastula’s surface.
• This is accomplished through the utilization of specific essential stains, including neutral red, Nile blue sulphate, and Bismarck brown. It was initially prepared by W. Vogt in 1929.

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