NEET 2024 — Zoology

The pons connects different regions of the brain (III); the hypothalamus carries neurosecretory cells (IV); the medulla controls respiration and gastric secretions (II); the cerebellum regulates posture and balance (I).

The Fallopian tube consists of the infundibulum, ampulla and isthmus. The fundus is the dome-shaped upper part of the uterus, not the tube.

Ti stands for tumour-inducing: the plasmid of Agrobacterium tumefaciens that causes crown gall, disarmed and used as a vector for plant transformation.

Expiratory capacity $=\mathrm{TV}+\mathrm{ERV}$ (II); functional residual capacity $=\mathrm{ERV}+\mathrm{RV}$ (IV); vital capacity $=\mathrm{ERV}+\mathrm{TV}+\mathrm{IRV}$ (I); inspiratory capacity $=\mathrm{TV}+\mathrm{IRV}$ (III).

FSH acts on ovarian follicles in females but on Sertoli cells in males; Leydig cells respond to LH — so A is false. Growing follicles do secrete oestrogen and interstitial (Leydig) cells do secrete androgens — R is true.

Lipase breaks ester bonds (II); nucleases break phosphodiester bonds (IV); proteases break peptide bonds (I); amylase breaks glycosidic bonds (III).

Chronological order: Homo habilis (~2 mya) → Homo erectus (~1.5 mya) → Neanderthal man (~100,000 years ago) → Homo sapiens. So A-D-C-B.

Myasthenia gravis, rheumatoid arthritis and SLE are autoimmune disorders. Gout is a metabolic disorder (urate crystals); muscular dystrophy is genetic.

The common cold is caused by rhinoviruses (III); haemozoin is the toxin released by Plasmodium (I); the Widal test diagnoses typhoid (II); dust mites are a common allergen (IV).

The axoneme is the core of cilia and flagella (II); the cartwheel pattern is the centriole's structure (I); cristae are the mitochondrial inner-membrane folds (IV); the satellite is a chromosome region beyond a secondary constriction (III).

Pleurobrachia is a ctenophore (II); the radula is the molluscan rasping organ (I); the stomochord is the buccal diverticulum of hemichordates (IV); the air bladder is found in bony fishes, Osteichthyes (III).

Skeletal muscle (voluntary) forms the triceps; smooth muscle lines the stomach; cardiac muscle is confined to the heart. The other sets misplace smooth muscle in the heart or skeletal muscle in bone.

Diakinesis: terminalisation of chiasmata (II). Pachytene: recombination nodules appear (IV). Zygotene: synaptonemal complex forms (I). Leptotene: chromosomes look like thin threads (III).

Down's syndrome is trisomy 21 (III). The $\beta -$globin gene is on chromosome 11 (I) and the $\alpha -$globin genes on chromosome 16 (IV). Klinefelter's syndrome involves an extra X chromosome (II).

Bioreactors are for large-scale production — hundreds to thousands of litres — not small cultures. The other three statements correctly describe a stirred-tank bioreactor.

Pterophyllum is the angel fish (III); Myxine the hag fish (I); Pristis the saw fish (II); Exocoetus the flying fish (IV).

In pBR322 the rop gene codes for proteins involved in plasmid replication, and ori controls copy number; the antibiotic-resistance genes are amp^R and tet^R. With X labelled at ori and Y at rop in the figure, X controls copy number and Y codes for a replication protein.

The hymen can be torn by sport, a fall or tampon use, and may persist after coitus — so its presence or absence indicates nothing about virginity (Statement I true) and it is not torn 'during the first coitus only' (Statement II false).

Annelids are true coelomates (A true). Poriferans lack a body cavity, aschelminthes are pseudocoelomates and platyhelminthes are acoelomates — B, C and D are all wrong.

The descending limb of the loop of Henle is permeable to water but nearly impermeable to electrolytes — the reverse of Statement I. The PCT is lined by simple cuboidal brush-border epithelium, not columnar — Statement II is also false.

The cell cycle runs $G_1\to S\to G_2\to M$, and M phase is karyokinesis followed by cytokinesis: E, C, A, D, B.

In both sexes of the cockroach a pair of jointed anal cerci arises from the 10th abdominal segment; anal styles (males only) are on the 9th.

Fibrous joints in the skull allow no movement (III); cartilaginous joints between vertebrae allow limited movement (I); the knee is a hinge joint (IV); the shoulder (humerus–pectoral girdle) is a ball-and-socket joint allowing rotation (II).

Glucagon is a peptide hormone from the pancreatic $\alpha -$cells. Testosterone, progesterone and cortisol are all steroids derived from cholesterol.

The impulse starts at the SA node, reaches the AV node, passes down the AV bundle, splits into the bundle branches and spreads through the Purkinje fibres: E, C, A, D, B.

Lippes loop is a non-medicated IUD (III); Multiload 375 releases copper (I); LNG-20 releases a hormone (IV); implants deliver progestogens (II).

Periodic abstinence, lactational amenorrhea and coitus interruptus are natural methods. Vaults are barrier devices placed over the cervix.

RNA polymerase reads the template 3′→5′ and builds a complementary RNA 5′→3′ with U in place of T: 3′-TACATGGCAAATATCCATTCA-5′ gives 5′-AUGUACCGUUUAUAGGUAAGU-3′.

Hardy–Weinberg equilibrium is disturbed by gene migration, genetic drift, mutation, recombination and natural selection. A constant gene pool is the condition of equilibrium itself, not a disturbance.

Cocaine comes from Erythroxylum coca (III); heroin (diacetylmorphine) from the opium poppy Papaver somniferum (IV); morphine is used as a sedative and painkiller in surgery (I); marijuana from Cannabis sativa (II).

Typhoid is bacterial, Salmonella typhi (IV); leishmaniasis is protozoan (III); ringworm is fungal, Microsporum and Trichophyton (I); filariasis is caused by the nematode Wuchereria (II).

$\alpha -1$ antitrypsin is used to treat emphysema (III); cry IAb controls corn borer (IV); cry IAc controls cotton bollworm (I); enzyme replacement therapy treats ADA deficiency (II).

Colostrum, the first milk, carries IgA antibodies that protect the newborn — which is exactly why breast-feeding in the first days is recommended. Both A and R are correct and R explains A.

Penguins (birds) and dolphins (mammals) evolved flippers independently for the same aquatic function — analogous organs, i.e. convergent evolution.

In the alveoli, high $p{\mathrm{O}}_2$, low $p\mathrm{C}{\mathrm{O}}_2$, lower ${\mathrm{H}}^{+}$ concentration and lower temperature all favour binding of oxygen to haemoglobin.

Goblet cells are unicellular glands (III); the moist buccal lining is compound epithelium (IV); salivary glands are multicellular exocrine glands (I); the pancreas contains endocrine glandular epithelium, the islets (II).

Juxtamedullary nephrons have their renal corpuscles close to the cortex–medulla junction and long loops of Henle that run deep into the medulla, which lets them concentrate urine. Cortical nephrons are far more numerous.

Spermatogonia are stimulated by FSH acting on Sertoli cells; LH (ICSH) acts on Leydig cells; Sertoli cells nourish the developing germ cells; the final transformation of spermatids into spermatozoa is spermiogenesis. Reading the flow chart's blanks in order gives FSH, Leydig cells, Sertoli cells, spermiogenesis.

The P wave is atrial depolarisation (III); the QRS complex, ventricular depolarisation (II); the T wave, ventricular repolarisation (IV); in the T–P gap the heart is electrically silent (I).

Bone marrow is the primary lymphoid organ where all blood cells including lymphocytes are made (I true), and both bone marrow and thymus provide the micro-environment for lymphocyte maturation — T cells maturing in the thymus (II true).

Gause's principle concerns species competing for the same limited resource — Statement I, which says 'different resources', is wrong. That the inferior competitor is eliminated when resources are limiting is a correct reading of the principle — Statement II is true.

Exophthalmic goitre (Graves' disease): hyperthyroidism with protruding eyes (III). Acromegaly: excess growth hormone in adults (IV). Cushing's syndrome: excess cortisol, moon face, hyperglycaemia (I). Cretinism: hypothyroidism in infancy with stunted growth (II).

The crop stores food (IV); the gastric caeca are the 6–8 blind tubules at the foregut–midgut junction (II); the Malpighian tubules are the 100–150 yellow filaments at the midgut–hindgut junction (III); the gizzard grinds food (I).

An O-group child (ii) must receive an i allele from each parent, so the B⁺ father is ${\mathrm{I}}^{\mathrm{B}}\mathrm{i}$ and the A⁺ mother ${\mathrm{I}}^{\mathrm{A}}\mathrm{i}$. Only set A fits; the other sets give at least one parent no i allele or the child a wrong genotype.

RNA polymerase III transcribes tRNA, 5S rRNA and snRNAs (IV); rho factor terminates transcription in prokaryotes (III); snRNPs carry out splicing (I); the TATA box is part of the promoter (II).

Mesozoic: age of reptiles and first birds (III); Proterozoic: lower invertebrates (I); Cenozoic: age of mammals (IV); Paleozoic: fishes and amphibians (II).

The corpus callosum is the tract joining the two cerebral hemispheres (Statement I true). The brain stem is the midbrain, pons and medulla — not the cerebrum — so Statement II is false.

The catalytic cycle: substrate binds the active site (E) → enzyme–substrate complex forms (A) → the enzyme strains the substrate's bonds, which break (D) → products are released (C) → the free enzyme is ready for another substrate (B).

Both mitochondria and chloroplasts are double-membrane-bound organelles (Statement I correct). NCERT describes the chloroplast's inner membrane as the relatively less permeable one, so Statement II, which says the reverse, is incorrect.

Non-chordates lack a notochord (B), have a dorsal heart if any (D) and no post-anal tail (E). Their central nervous system is ventral, and the pharynx is not perforated by gill slits — A and C are chordate features.