Evolution: NEET PYQ, 2018–2026

Answer: (A)

Neanderthals lived in Europe and Western Asia during the Late Pleistocene. Their fossils were first found in the Neander valley in Germany, which gave the species its name. Associating a species with its fossil location is a common question type, so learn the main regions for each human ancestor.

Answer: (B)

Principle: Homo sapiens evolved in Africa and spread to other continents later. Apply: the earliest fossils are African, so Africa is the origin. Students who pick Europe or Java mix up Neanderthals or Homo erectus with modern humans. Students who pick Central Asia assume the place of later dispersal is the place of origin.

Answer: (A)

The recessive phenotype appears only in aa individuals, whose frequency is q². So q² = 0.16, q = 0.4, and p = 1 − q = 0.6.

Answer: (A)

Principle: the Hardy-Weinberg principle holds only when there is no mutation, no migration, no natural selection, no genetic drift, and random mating in a large population. Apply: of the options, only random mating is one of these five conditions. The other three are evolutionary forces that the principle assumes are absent.

Answer: (A)

The principle is that the first life was heterotrophic because the early earth had accumulated organic molecules from abiotic synthesis. These molecules served as food. Autotrophy, whether photosynthetic or chemosynthetic, came later and built on this supply. Option A states the heterotrophic mode directly. The distractors mix up nutritional modes (photosynthesis and chemosynthesis) or assume a cellular metabolism that was not yet in place.

Answer: (C)

For an X-linked locus, males have one X and so their phenotype frequency equals the allele frequency: q = 0.08 and p = 0.92. Females have two X chromosomes, so genotype frequencies among females follow Hardy-Weinberg: p squared for XAXA, 2pq for carriers XAXc, and q squared for affected XcXc. Carrier females are therefore 2pq = 2(0.92)(0.08) = 0.1472. Students must remember that the X-linked allele frequency applies to both sexes, but the genotype frequencies must be computed separately for females.

Answer: (A)

Since q squared = 0.04, q = 0.2 and p = 0.8. Individuals with the dominant phenotype are AA and Aa, so their frequency is p squared plus 2pq, which equals 1 minus q squared = 1 minus 0.04 = 0.96.

Answer: (B)

Five factors are known to affect the Hardy–Weinberg equilibrium: gene migration or gene flow, genetic drift, mutation, genetic recombination and natural selection. Random mating in a large population is one of the conditions under which the equilibrium holds.

Answer: (A)

Principle: transitional fossils show mosaic features, a combination of ancestral and derived traits, which together indicate a link between two groups without necessarily being the direct ancestor of any living group. Apply: Archaeopteryx has reptilian teeth and a bony tail alongside avian feathers and wings, so it documents the reptile–bird transition. Its age alone does not make it a direct ancestor. Option C confuses homology with analogy and misreads the fossil's flight capacity. Option D uses a misleading single trait and mistakes teeth as a mammalian marker.

Answer: (A)

Sedimentary rocks form by layer-by-layer deposition, so in undisturbed strata the deeper layers are older. Fossils in those layers are therefore relatively older. This principle of superposition gives relative ages of fossils and shows how life forms changed over time.