NEET 2025 Biology Questions with Solutions

Explanation

Vitamin B₁₂ deficiency causes pernicious anaemia, Vitamin D deficiency causes rickets, Vitamin B₂ deficiency causes cheilosis, and Vitamin B₆ deficiency can cause convulsions. Hence the correct matching is A-IV, B-III, C-I, D-II.

Explanation

Complex II of the mitochondrial electron transport chain is succinate dehydrogenase. It participates in both the Krebs cycle and electron transport chain.

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In PCR, the DNA doubles after every cycle. Therefore, after n cycles, amplification follows the expression 2ⁿ.

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IVF requires expensive instruments and reagents, may reduce adoption of orphans, and the embryo may fail to survive during early development. High fatality risk and non-availability in India are incorrect statements.

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In frogs, deoxygenated blood from the body returns to the heart through the vena cava.

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Reductionist biology explains biological phenomena through physical and chemical principles.

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RNA is believed to be the first genetic material and is chemically reactive. DNA evolved later as a more stable genetic material with repair mechanisms.

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In commensalism, one organism benefits while the other is neither harmed nor benefited. Epiphytes gain support from the mango tree without affecting it.

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Eukaryotic ribosomes are 80S (60S + 40S) and prokaryotic ribosomes are 70S (50S + 30S). Ribosomes consist of two subunits.

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Ex-situ conservation involves conservation of organisms outside their natural habitat. Zoos and botanical gardens are examples of ex-situ conservation.

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Solar energy is the primary source of energy in an ecosystem, so Statement I is correct. Statement II is incorrect because the total rate of organic matter production during photosynthesis is called Gross Primary Productivity (GPP), not Net Primary Productivity (NPP).

Explanation

Emphysema is associated with damaged alveolar walls and decreased respiratory surface. Angina pectoris refers to chest pain due to insufficient oxygen supply to heart muscles. Glomerulo-nephritis is inflammation of glomeruli of kidney. Tetany involves rapid muscle spasms due to low calcium levels.

Explanation

Wind and water pollinated flowers are generally not colourful and do not produce nectar because they do not require animal attraction. They also produce enormous amounts of pollen grains to ensure successful pollination. However, the large production of pollen is not the direct reason for lack of colour and nectar.

Explanation

Beer is a non-distilled alcoholic beverage produced by yeast fermentation. Whisky, brandy, and rum are distilled alcoholic beverages.

Explanation

In floral formula, ⊕ represents actinomorphic symmetry, not zygomorphic symmetry. G with a line below indicates superior ovary. Hence Statement I is incorrect and Statement II is correct.

Explanation

Streptokinase produced by Streptococcus is used as a clot buster for removing blood clots from blood vessels.

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Chromosome 1 has the highest number of genes in the human genome.

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In male frogs, copulatory pads are present on the first digit of the forelimbs and help in holding the female during amplexus.

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Cytokinins promote nutrient mobilization and delay leaf senescence in plants.

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In pseudocoelomates, mesoderm lines the body wall but not the alimentary canal completely.

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Head contains genetic material, middle piece provides energy through mitochondria, acrosome contains enzymes, and tail helps in sperm motility.

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In pteridophytes, meiosis forms spores, spores develop into prothallus, gametophytes produce archegonia and antheridia, antherozoids transfer through water, and fertilisation occurs.

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Cardiac activity is regulated by nodal tissue, medulla oblongata, and adrenal medullary hormones. Adrenal cortical hormones are not directly involved.

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Volvox is a green alga and cannot fix atmospheric nitrogen. Azotobacter, Oscillatoria, Anabaena and Nostoc are associated with nitrogen fixation.

Explanation

tRNA and rRNA interact with mRNA during translation, so Statement I is incorrect. RNA interference is a cellular defence mechanism found in eukaryotes, so Statement II is correct.

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Insertion of foreign DNA at the EcoRI site within the β-galactosidase gene disrupts its function. Recombinant colonies cannot produce β-galactosidase and therefore appear white in blue-white screening.

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Eli Lilly used genetically engineered Escherichia coli bacteria to produce human insulin.

Explanation

Transferases catalyze the transfer of a functional group from one substrate to another.

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In monocot stems, the hypodermis is sclerenchymatous, not parenchymatous. The other statements are correct features of monocot stems.

Explanation

Bryophyte life cycle proceeds as: attachment of gametophyte to substratum, release of antherozoids into water, fertilization, formation of sporophyte, and finally meiosis to produce haploid spores.

Explanation

Computed tomography (CT) and magnetic resonance imaging (MRI) are used to detect cancers of internal organs. α-interferon activates the immune system and helps destroy tumours. Chemotherapeutic drugs target cancerous cells, not non-cancerous cells, and biological response modifiers are different from chemotherapeutic drugs. In leukaemia, blood cell counts are generally abnormally high, not decreased.

Explanation

Centromere is associated with cell division, cilium helps in cell movement, cristae are structures present in mitochondria, and the cell membrane is composed of a phospholipid bilayer.

Explanation

Chlorophyll a is blue-green, chlorophyll b is yellow-green, xanthophylls are yellow pigments, and carotenoids are yellow to yellow-orange pigments.

Explanation

In human pregnancy, major organ systems are formed by the end of 12 weeks. Limbs and digits develop by the end of the second month, and appearance of hair is usually observed during the fifth month. Hence statements A, C, D and E are considered correct according to the answer key.

Explanation

In cereal seeds, the outermost layer of the endosperm is a protein-rich layer called the aleurone layer.

Explanation

The proximal convoluted tubule mainly reabsorbs NaCl, HCO3⁻ and water, while the distal convoluted tubule is involved in selective secretion and absorption of ions such as K+ and H+. Therefore, option (B) is correct according to the answer key.

Explanation

In a stirred tank bioreactor, the foam breaker is located near the top region of the reactor to prevent excessive foam formation during fermentation. In the given diagram, label C represents the foam breaker.

Explanation

A typical mature embryo sac of angiosperms is 8-nucleate and 7-celled. The egg apparatus consists of one egg cell and two synergids, while the two polar nuclei are present in the central cell. Hence Assertion is true but Reason is false.

Explanation

Mesosomes are infoldings of the plasma membrane in prokaryotic cells. They help in cell wall formation, DNA replication and respiration.

Explanation

Post-transcriptional modifications in eukaryotes include splicing (removal of introns and joining of exons), 5’ capping by addition of a methylated guanosine cap, and 3’ polyadenylation by addition of adenine residues. Hence B, C and D are correct.

Explanation

Polygenic inheritance involves multiple genes contributing to a single trait and does not follow simple Mendelian ratios. Therefore, it is a non-Mendelian inheritance pattern.

Explanation

Catalase is a haem-containing enzyme that catalyzes the decomposition of hydrogen peroxide into water and oxygen.

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Increasing order of complexity is: C → Monera (prokaryotes) E → Protista (cellular eukaryotes) A → Fungi D → Plantae B → Animalia Hence, the correct order is C, E, A, D, B.

Explanation

Ramdeo Misra is known as the father of Ecology in India due to his pioneering work in Indian ecology.

Explanation

Hershey and Chase confirmed DNA as genetic material. Euchromatin is loosely packed and light-stained. Frederick Griffith worked on Streptococcus pneumoniae. Heterochromatin is densely packed and dark-stained.

Explanation

Neoplastic cells show uncontrolled proliferation, rapid growth, and invasion of surrounding tissues. Cells confined to the original location are benign and not characteristic of malignant neoplasia.

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DNA fragments isolated after gel electrophoresis can be used to construct recombinant DNA. In agarose gel electrophoresis, smaller fragments move faster towards the anode, while larger fragments remain near the wells.

Explanation

Adenosine is a nucleoside, adenylic acid is a nucleotide, adenine is a nitrogenous base, and alanine is an amino acid.

Explanation

In females, meiosis begins during fetal development, whereas in males it begins at puberty, so statement A is true. The interval between meiosis I and meiosis II is very short in males but can extend for years in females, making statement B true. The first polar body forms after completion of meiosis I from the primary oocyte, so statement C is false. LH surge causes ovulation, not menstrual bleeding; menstruation occurs due to reduction in progesterone levels, so statement D is false.

Explanation

All living members of Cyclostomata are ectoparasites on some fishes. They possess a sucking and circular mouth without jaws.

Explanation

The Golgi apparatus modifies, packages and transports materials synthesized in the endoplasmic reticulum. ER vesicles fuse with the cis face of the Golgi body, and processed products are released through the trans face. Hence both Assertion and Reason are true, and Reason correctly explains Assertion.

Explanation

Scutellum is the cotyledon of a monocot seed. Groundnut is a non-albuminous seed. Epiblast is a rudimentary cotyledon in grasses. Perisperm represents the persistent nucellus.

Explanation

Vertebrates belong to phylum Chordata because they possess a notochord during embryonic development. In adults, the notochord is replaced by a vertebral column. However, some chordates like urochordates and cephalochordates do not possess vertebral columns, so not all chordates are vertebrates.

Explanation

The antigen-binding site of an antibody is present at the variable region near the N-terminal ends of heavy and light chains, not at the C-terminal region. Hence statement 3 is incorrect.

Explanation

RNA interference (RNAi) occurs due to the presence of complementary double stranded RNA (dsRNA), which binds to specific mRNA and prevents its translation, thereby silencing gene expression.

Explanation

A dihybrid cross involving two independently assorting genes produces the classical Mendelian phenotypic ratio of 9 : 3 : 3 : 1 in the F2 generation.

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Histone proteins are rich in basic amino acids lysine and arginine, which help them bind strongly to negatively charged DNA.

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The first menstrual flow in human females is called menarche. It marks the beginning of reproductive maturity.

Explanation

Heart secretes atrial natriuretic factor, kidney secretes erythropoietin, gastro-intestinal tract secretes secretin, and adrenal cortex secretes aldosterone.

Explanation

The protein part of an enzyme is called apoenzyme. The complete functional enzyme formed with its cofactor is called holoenzyme.

Explanation

Productivity of an ecosystem is measured as the rate of biomass or energy production per unit area per unit time. Therefore, the correct unit is (KCal m⁻²) yr⁻¹.

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Sweet potato is a modified root while potato is a modified stem. They perform similar functions but have different origins, making them analogous organs formed due to convergent evolution.

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From the pedigree, the trait follows an autosomal recessive inheritance pattern. Crossing between a carrier female and affected male gives offspring probabilities of 1/2 carrier and 1/2 affected. Considering unaffected carrier condition specifically, the probability becomes 1/4.

Explanation

Tapetal cells are metabolically active cells with dense cytoplasm and often multinucleate condition. This multinucleate nature helps in efficient nourishment and development of microspores during pollen formation.

Explanation

The megaspore mother cell undergoes one meiotic division to form four megaspores. One functional megaspore then undergoes three successive mitotic divisions to form the mature female gametophyte (embryo sac).

Explanation

Pea flower exhibits bilateral symmetry and is therefore zygomorphic. Petunia, Datura, and Chilli are actinomorphic flowers.

Explanation

Secondary lymphoid organs include spleen, lymph nodes, tonsils, and Peyer's patches. Thymus and bone marrow are primary lymphoid organs.

Explanation

The fig–fig wasp association is a classic example of mutualism, making statement II correct biologically. However, statement I is incorrect because figs consumed commercially generally do not contain enclosed wasps in the edible fruit.

Explanation

Spindle fibers attach to chromosomes at the centromere and help separate sister chromatids during mitosis.

Explanation

Gymnosperms are characterized by naked seeds that are not enclosed within fruits.

Explanation

Adrenal medullary hormones (adrenaline and noradrenaline) are hyperglycemic hormones, cause piloerection, and increase the strength of heart contraction. They do not cause pulmonary constriction.

Explanation

Insulin is a protein hormone. If taken orally, digestive enzymes in the gastrointestinal tract break it down before it can enter the bloodstream.

Explanation

Salvinia is a pteridophyte, Polytrichum is a bryophyte, Salvia is an angiosperm, and Ginkgo is a gymnosperm.

Explanation

George Gamow proposed that the genetic code is triplet in nature, consisting of three nucleotides coding for one amino acid.

Explanation

The Evil Quartet refers to causes of biodiversity loss, ex situ conservation includes cryopreservation, Lantana camara is an alien invasive species, and Dodo is an extinct species.

Explanation

ADH is synthesized in the hypothalamus and stored and released from the posterior pituitary gland.

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The water vascular system in echinoderms helps in locomotion, respiration, and capture and transport of food.

Explanation

Innate immunity is present from birth and provides non-specific defense against pathogens.

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Gemmae are multicellular green structures found in bryophytes that help in vegetative propagation, which is a form of asexual reproduction.

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The renal portal system in frog carries blood from the posterior part of the body to the kidneys before returning it to circulation.

Explanation

RuBisCO catalyzes the carboxylation of ribulose bisphosphate (RuBP) during the Calvin cycle in photosynthesis.

Explanation

Restriction enzymes, DNA ligase and DNA polymerase are commonly used in gene cloning. DNA mutase and DNA recombinase are not essential enzymes for the cloning process.

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Auxins can induce parthenocarpy. Plant growth regulators may promote or inhibit growth. Dedifferentiation precedes redifferentiation. ABA is mainly a growth inhibitor, and apical dominance suppresses lateral bud growth.

Explanation

Rho (ρ) factor is involved in rho-dependent termination of transcription in prokaryotes.

Explanation

In water, frogs respire mainly through skin. On land, respiration occurs through skin, buccal cavity and lungs. Hence the statement is false for water but true for land.

Explanation

A boy and a girl twin pair cannot be monozygotic because monozygotic twins arise from the same zygote and therefore have the same sex. Hence, they must be fraternal (dizygotic) twins.

Explanation

Aspergillus niger is mainly used for citric acid production and Trichoderma polysporum is used in cyclosporin-A production. These are industrial products, not household products. Lactobacillus, Saccharomyces cerevisiae, and Propionibacterium sharmanii are involved in curd, bread/fermentation, and cheese preparation respectively.

Explanation

Progesterone is secreted by corpus luteum, relaxin by ovary, melanocyte stimulating hormone by pars intermedia, and catecholamines by adrenal medulla.

Explanation

In blue-white screening, recombinant colonies contain inserted DNA that disrupts the lacZ gene and therefore appear white. Non-recombinant colonies retain lacZ activity and appear blue.

Explanation

The Verhulst-Pearl logistic growth equation is: $$\frac{dN}{dt} = rN\left(\frac{K-N}{K}\right)$$ where N is population size, r is intrinsic rate of increase, and K is carrying capacity.