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Evolution is a chapter students read as a story and then lose marks on, because the questions are not about the story. They ask you to calculate carrier frequencies, decide whether two organs are homologous, or spot the flawed explanation of selection among four options. This post gives you a method for each.
What does the NEET syllabus include?
The NEET (UG)-2026 syllabus lists the origin of life, evidence for evolution (palaeontology, comparative anatomy, embryology and molecular evidence), Darwin's contribution, the modern synthetic theory, variation, natural selection with examples and its types, gene flow and genetic drift, the Hardy-Weinberg principle, adaptive radiation and human evolution. The matching NCERT chapter is Evolution, Chapter 6 of Class 12 biology. Check the syllabus for your own exam year when NMC publishes it.
Why do students get natural selection wrong?
Bishop and Anderson (1990) tested college students before and after a course on evolution. Most students thought of traits changing because a species needed them to, gave no role to variation within a population or to differences in reproductive success, and pictured all members of a population changing gradually together. Students had taken nearly two years of biology on average, and that prior study made no difference to their scores.
Every correct answer about selection contains three parts:
Variation: individuals already differ, because of mutation and recombination.
Selection: some variants survive and reproduce more in that environment.
Inheritance: their offspring carry those variants, so the proportion changes over generations.
If an option says "the moths turned dark to hide", it fails part 1. Individuals did not change; the population's mix did.
What does the peppered moth example actually show?
NCERT describes collections made in England: in the 1850s, before industrialisation, white-winged moths outnumbered dark ones, and by 1920 dark moths were more common in industrial areas, where soot had darkened tree trunks. H. B. D. Kettlewell ran selection experiments on industrial melanism in the 1950s. Later critics questioned his methods, so Michael Majerus ran a larger test. His results, analysed and published by Cook and colleagues (2012), came from 4,864 moths released over six years. Birds took more of the dark moths, and the strength of selection was enough to explain why dark moths declined once the air became cleaner.
How do you solve Hardy-Weinberg problems?
NCERT states the principle: allele frequencies stay constant across generations unless something disturbs them. For a gene with alleles A (frequency p) and a (frequency q), p + q = 1 and the genotype frequencies are p² (AA), 2pq (Aa) and q² (aa). The principle was set out by G. H. Hardy in Science in 1908.
Worked example. In a population of 500 people, 16% show a recessive trait. How many are carriers?
Recessive phenotype means aa, so q² = 0.16.
q = √0.16 = 0.4.
p = 1 − 0.4 = 0.6.
Carriers (Aa): 2pq = 2 × 0.6 × 0.4 = 0.48, so 0.48 × 500 = 240 people.
Check: AA = 0.36 × 500 = 180, aa = 80. 180 + 240 + 80 = 500.
Mistakes that cost marks:
Taking q = 0.16 instead of its square root.
Using pq instead of 2pq for heterozygotes.
Treating the dominant phenotype percentage as p². It is p² + 2pq.
NCERT names five factors that disturb the equilibrium: gene flow, genetic drift, mutation, genetic recombination and natural selection. Small migrating groups can show the founder effect.
How do you tell homologous from analogous organs?
Homologous organs share an anatomical plan but may do different jobs, and point to common ancestry by divergent evolution. NCERT's examples: the forelimbs of whales, bats, cheetahs and humans, all with humerus, radius, ulna, carpals, metacarpals and phalanges, and the thorn of *Bougainvillea* and tendril of *Cucurbita*. Analogous organs do similar jobs with different structures, by convergent evolution: wings of butterflies and birds, eyes of octopus and mammals, flippers of penguins and dolphins, and the sweet potato (a root) and potato (a stem).
Ask one question: is the structure the same, or only the job? Same structure means homologous.
For origin of life questions, know NCERT's account of S. L. Miller's 1953 experiment: an electric discharge in a closed flask of methane, hydrogen, ammonia and water vapour produced amino acids. The original paper is Miller (1953) in Science.
A practice routine for evolution
Three Hardy-Weinberg problems every other day, starting from q², from p, and from the number of carriers.
Rewrite five wrong explanations of selection so each has variation, selection and inheritance.
Make a two-column homology and analogy table from memory, then check it against NCERT.
Sketch stabilising, directional and disruptive selection as shifting bell curves, labelled.
When a problem stalls and you cannot see the next step, the Fermi Problem Library has a step-by-step solver that explains the reasoning rather than printing an answer. For the history behind the theory, read our profile of Darwin, Wallace and natural selection.
Today, solve the carrier problem again with 9% showing the recessive trait, then check that your three genotype counts add up.
