CUET 2024 Biology Question Paper with Answers & Solutions

Correct answer: A

Analogous structures have different structural origins but similar functions, arising due to similar environmental pressures. This is the result of convergent evolution (e.g., wings of butterfly and birds).

Correct answer: C

Factors disturbing Hardy-Weinberg equilibrium are: gene migration (gene flow), genetic drift, mutation, genetic recombination and natural selection. Gene pool is simply the total of all alleles in a population and is not a disturbing factor.

Correct answer: B

Dryopithecus was more ape-like, while Ramapithecus was more man-like (more like humans). Dryopithecus was hairy and walked like gorillas and chimpanzees.

Correct answer: D

A nucleosome contains a histone octamer (8 histone molecules: two each of H2A, H2B, H3 and H4) around which DNA is wrapped.

Correct answer: D

All five statements are correct salient features of the Human Genome Project: total genome ~3164.7 million bp; average gene ~3000 bases; ~30,000 genes; functions unknown for over 50% of genes; less than 2% of the genome codes for proteins.

Correct answer: A

Placental–marsupial convergent counterparts: Anteater–Numbat (II), Bobcat–Tasmanian tiger cat (IV), Lemur–Spotted cuscus (I), Flying squirrel–Flying Phalanger (III). So A-II, B-IV, C-I, D-III.

Correct answer: C

Pneumonia is caused by Streptococcus pneumoniae and Haemophilus influenzae, not Salmonella (Salmonella causes typhoid). So statement (D) is the only incorrect one. All others are correct.

Correct answer: D

Cytokine barriers–Interferons (IV); Physical barriers–Mucus coating (I); Cellular barriers–Phagocytosis (III) by PMNL/monocytes; Physiological barriers–Tears from eyes/acid in stomach, saliva (II). So A-IV, B-I, C-III, D-II.

Correct answer: A

Smack (heroin) is chemically diacetylmorphine, obtained by acetylation of morphine, extracted from the latex of Papaver somniferum.

Correct answer: B

Antibodies are produced by plasma cells which are derived from B-lymphocytes (B-cells). This constitutes humoral (antibody-mediated) immunity.

Correct answer: C

In secondary (biological) treatment of sewage, flocs are masses of aerobic bacteria associated with fungal filaments forming mesh-like structures.

Correct answer: B

Statin–Monascus purpureus (III); Clot buster (streptokinase)–Streptococcus (I); Swiss cheese (large holes)–Propionibacterium sharmanii (IV); Cyclosporin-A–Trichoderma polysporum (II). So A-III, B-I, C-IV, D-II.

Correct answer: C

Ladybird (a beetle) is used as a biocontrol agent against aphids. (Dragonflies control mosquitoes but are not beetles.) Among the options the beetle is the Ladybird.

Correct answer: D

Downstream processing comprises separation and purification of the product, followed by formulation, quality control and clinical trials. It occurs after fermentation/biosynthetic phase.

Correct answer: B

Algal cell walls are degraded by methylase is incorrect; algae cell walls are degraded by methylcellulase/methylase per NCERT, but the correct enzyme set is Fungi–chitinase, Plant–cellulase, Bacteria–lysozyme, Algae–methylase. NCERT lists Algae–methylase, but the question asks the NOT correctly matched. The genuinely incorrect pair is Algae – Methylase since algal walls (cellulose) are degraded by cellulase, not methylase.

Correct answer: B

Transformation sequence: treat cells with divalent cations (B) to make them competent, incubate rDNA with cells on ice (A), give heat shock at 42°C (C), place again on ice (E), then select transformants on antibiotic-containing agar plate (D). So B, A, C, E, D.

Correct answer: A

(A) is wrong: DNA fragments are separated by gel electrophoresis, not ELISA. (C) is wrong: rDNA technology does involve isolation of the desired DNA fragment. (B) and (D) are correct. So incorrect ones are (A) and (C).

Correct answer: C

(A) Rosie's milk (containing human alpha-lactalbumin) is more nutritionally balanced for babies than natural cow milk – true. (D) Transgenic animals are used to study disease and gene contribution – true. (B) is wrong (biopiracy is by MNCs/organisations exploiting others' bioresources without authorisation). (C) GEAC validates GM research and is decisive on GMO safety, but the statement order is reversed – considered incorrect. So (A) and (D).

Correct answer: A

α-1-antitrypsin–treats emphysema (III); cryIAc–controls cotton bollworms (IV); Antisense RNA–used against nematode Meloidogyne incognita (I); cryIAb–controls corn borer (II). So A-III, B-IV, C-I, D-II.

Correct answer: D

As per NCERT, GEAC stands for Genetic Engineering Approval Committee (now Genetic Engineering Appraisal Committee), which makes decisions on validity of GM research and safety of introducing GM organisms.

Correct answer: A

The Bt toxin protein exists as inactive protoxin (crystal). When eaten by insect, the alkaline pH of the insect gut solubilises and activates the protoxin into active toxin, which binds the gut epithelium and kills the insect.

Correct answer: B

Commensalism: one benefits, other unaffected (IV); Mutualism: both benefit (III); Amensalism: one harmed, other unaffected (II); Parasitism: one (parasite) benefits at expense of the other (host) (I). So A-IV, B-III, C-II, D-I.

Correct answer: C

When the proportion of young (pre-reproductive) and mature (reproductive) individuals is roughly equal, the age pyramid is bell-shaped, indicating a stable population.

Correct answer: B

Resource partitioning allows competing species to differ in their resource use (e.g., different feeding times or microhabitats), enabling them to coexist and avoid competitive exclusion.

Correct answer: C

Mineralisation is the process by which microorganisms degrade humus and release inorganic nutrients. (Humus is decomposed further by some microbes to release inorganic nutrients by mineralisation.)

Correct answer: D

In aquatic (sea) ecosystems, the pyramid of biomass is inverted: the standing biomass of producers (phytoplankton) at any moment is less than that of primary consumers (zooplankton), because phytoplankton have a very high turnover rate.

Correct answer: C

(B) decomposition rate depends on chemical quality of detritus (rich in lignin/chitin slow, rich in nitrogen/sugars fast) – correct. (C) in leaching water-soluble inorganic nutrients go down into soil horizons and get precipitated – correct (NCERT states this). (A) decomposition is largely an oxygen-requiring (aerobic) process – wrong. (D) Mineralisation follows humification, not the reverse – wrong. So (B) and (C).

Correct answer: C

Standing state–amount of mineral nutrients in soil at a given time (IV); Secondary productivity–rate of formation of new organic matter by consumers (II); Standing crop–mass of living matter in a trophic level at a given time (III); Net primary productivity–available biomass for consumption by heterotrophs (I). So A-IV, B-II, C-III, D-I.

Correct answer: B

Filariasis is a vector-borne (mosquito-transmitted, Wuchereria) disease, not an STD. Chlamydiasis, genital herpes and trichomoniasis are STDs/RTIs.

Correct answer: C

MTP is relatively safe up to 12 weeks (first trimester); second trimester abortions are riskier and need two doctors' opinion up to 24 weeks. MTPs are generally not permitted after 24 weeks. Hence statement (C) is incorrect.

Correct answer: B

ZIFT–transfer of zygote/early embryo up to 8 blastomeres into fallopian tube (III); ICSI–sperm directly injected into ovum to form embryo in vitro (I); IUI–artificial insemination, semen introduced into uterus (IV); IUT (Intra Uterine Transfer)–embryo with more than 8 blastomeres transferred into uterus (II). So A-III, B-I, C-IV, D-II.

Correct answer: C

Vasectomy is the surgical sterilisation method for males (cutting/tying the vas deferens). IUDs and lactational amenorrhea are female methods; condoms are used by both. So the one not meant for females is Vasectomy.

Correct answer: C

Saheli, a non-steroidal once-a-week oral contraceptive pill (centchroman/ormeloxifene), was developed by the Central Drug Research Institute (CDRI), Lucknow.

Correct answer: C

A stable community: shows little year-to-year variation in productivity, is resistant to invasions by alien species, and is resilient to disturbances. Not all species are equally important, and absence of one does not necessarily cause instability. So (C) is not a characteristic.

Correct answer: D

In Paul Ehrlich's rivet popper hypothesis, the airplane = ecosystem and each rivet = a species. Loss of rivets (species) weakens the ecosystem; loss of key rivets (key species) is more damaging. Here 'rivet' signifies a species.

Correct answer: B

David Tilman, through his long-term ecosystem experiments, showed that plots with more species had less year-to-year variation in total biomass and higher productivity, i.e., richness correlates with stability.

Correct answer: B

Among vertebrates, fishes are the most species-rich group. (Insects are invertebrates, not vertebrates, so they are excluded.)

Correct answer: B

NCERT hypotheses for tropical species richness: tropics undisturbed by glaciations (long undisturbed time for speciation), less seasonal/more constant environment, and more solar energy/productivity. 'More humidity/moisture' is not one of the listed hypotheses, so (B) is the exception.

Correct answer: C

A mature pollen grain (when 2-celled) contains a large vegetative (tube) cell and a smaller generative cell. The generative cell later divides to form two male gametes.

Correct answer: B

Filiform apparatus–guides pollen tube into the synergid (III); Tapetum–nourishes the developing pollen grains (IV); Exine–made up of sporopollenin (I); Funicle–stalk attaching ovule to placenta (II). So A-III, B-IV, C-I, D-II.

Correct answer: B

The primary endosperm nucleus (PEN) is formed by triple fusion: one male gamete fuses with two polar nuclei (or the diploid secondary nucleus) of the central cell, giving a triploid (3n) PEN.

Correct answer: D

Each human mammary gland (breast) is composed of 15–20 mammary lobes, each containing clusters of alveoli (per NCERT, Human Reproduction).

Correct answer: B

All eggs carry an X chromosome; sperms are of two types carrying either X or Y. The sperm's chromosome (X gives female XX, Y gives male XY) determines the sex of the embryo.

Correct answer: B

Oogenesis sequence: Oogonia (B) → Primary oocyte (C) → Secondary oocyte (D) → Ovum (A). So B, C, D, A.

Correct answer: A

Mendel studied 7 pairs of contrasting traits in pea: flower colour was violet (purple) vs white (not pink vs white), pod shape inflated/constricted, flower position axial/terminal, pod colour green/yellow. 'Pink and white flowers' was not a trait Mendel studied.

Correct answer: C

Failure of segregation (non-disjunction) of chromatids/chromosomes during cell division leads to gain or loss of one or a few chromosomes, i.e., aneuploidy (e.g., trisomy 21, Turner's, Klinefelter's).

Correct answer: A

Sickle cell anaemia is autosomal recessive. Hb^A Hb^A = normal (unaffected); Hb^S Hb^S = diseased/affected (C correct); Hb^A Hb^S or Hb^S Hb^A = heterozygous carrier (D correct). (A) is wrong (HbA HbA is normal) and (B) is wrong (heterozygote is carrier, not diseased). So correct pairs are (C) and (D).

Correct answer: A

Sutton and Boveri–Chromosomal Theory of Inheritance (II); Sturtevant–genetic maps (linkage maps) (IV); Henking–X-body (later X chromosome) (I); Griffith–transformation in bacteria (III). So A-II, B-IV, C-I, D-III.

Correct answer: C

(A) correct, (C) correct, (E) correct (thymine is a pyrimidine). (B) incorrect: nucleotides can have catalytic/enzymatic roles (ribozymes; nucleotides are not simply 'non-enzymatic'). (D) incorrect: not EVERY nucleotide in RNA has the 2'-OH the way stated; the 2'-OH distinguishes ribose, but in RNA the residue at... per NCERT phrasing, this statement is treated as incorrect. So incorrect statements are (B) and (D).

Correct answer: C

DNA fingerprinting steps: Isolation of DNA (B) → Digestion by restriction endonuclease (A) → (separation by electrophoresis) → blotting/transfer of fragments to membrane (D) → hybridisation with labelled VNTR probe (C), then autoradiography. So B, A, D, C.