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Evolution

NCERT Class 12 Biology Chapter 6

Evolution for Class 12 Biology and NEET: origin of life, evidences, natural selection, Hardy–Weinberg principle, adaptive radiation and human evolution.

10 topics Updated 8 Nov 2026

For: Class 12 and NEET, unless a topic says otherwise

In the syllabus: NEET Class 12 syllabus

With your textbook

NCERT Biology (Class 12), Chapter 6 “Evolution”, reprint 2026-27.

Open the official NCERT chapter (PDF, 12.7 MB, ncert.nic.in)

Checked on 19 Oct 2026.

Learn in this order

  1. Origin of life

    Origin of life for Class 12 Biology and NEET: early earth, panspermia, Pasteur, chemical evolution and the Miller–Urey experiment, with a labelled diagram.

    NCERT Section 6.1 12 min read 3 solved examples 8 practice questions

  2. Evolution of life forms: Darwin’s theory

    Darwin’s theory of evolution for Class 12 Biology and NEET: special creation, Darwin’s voyage, reproductive fitness, natural selection and Wallace.

    NCERT Section 6.2 7 min read 3 solved examples 7 practice questions

  3. Evidences for evolution

    Evidences of evolution for Class 12 Biology and NEET: fossils, embryology, homologous and analogous organs, molecular evidence and industrial melanism.

    NCERT Section 6.3 14 min read 3 solved examples 8 practice questions

  4. Adaptive radiation

    Adaptive radiation for Class 12 Biology and NEET: Darwin’s finches of the Galapagos, Australian marsupials and convergent evolution with placental mammals.

    NCERT Section 6.4 7 min read 3 solved examples 7 practice questions

  5. Biological evolution

    Biological evolution for Class 12 Biology and NEET: natural selection and fitness, branching descent, Lamarckism against Darwinism and Malthus.

    NCERT Section 6.5 9 min read 3 solved examples 7 practice questions

  6. Mechanism of evolution

    Mechanism of evolution for Class 12 Biology and NEET: Hugo de Vries’ mutation theory from the evening primrose, saltation and Darwinian variation compared.

    NCERT Section 6.6 6 min read 2 solved examples 6 practice questions

  7. Hardy–Weinberg principle

    Hardy–Weinberg principle for Class 12 Biology and NEET: p + 2pq + q = 1, five factors, gene flow, drift, types of natural selection, solved examples.

    NCERT Section 6.7 15 min read 4 solved examples 8 practice questions

  8. Modern synthetic theory of evolution

    Darwin plus Mendel, its architects, five factors, isolation and speciation, solved examples.

    NEET only 12 min read 3 solved examples 8 practice questions

  9. A brief account of evolution

    Brief account of evolution for Class 12 Biology and NEET: NCERT’s dated timeline from the first cells to mammals, geological periods and solved examples.

    NCERT Section 6.8 15 min read 4 solved examples 8 practice questions

  10. Origin and evolution of man

    Human evolution for Class 12 Biology and NEET: NCERT’s early primates, australopithecines, brain sizes 650–1400 cc, Neanderthals and modern humans.

    NCERT Section 6.9 11 min read 3 solved examples 8 practice questions

Key formulas in this chapter

Origin of life

  • universe: about 13.8 billion years
  • earth: about 4.5 billion years
  • life appeared: about 4 billion years ago (NCERT)
  • Miller 1953: electric discharge → amino acids
  • first cells: about 2000 million years ago (NCERT); microbial evidence: at least about 3.5 billion years ago

Evolution of life forms

  • NCERT historical special-creation claim: 4000 years, not accepted Earth age
  • Darwin: voyage on H.M.S. Beagle
  • fitness = reproductive fitness
  • better fit leave more progeny: natural selection
  • Wallace: Malay Archipelago

Evidences for evolution

  • homologous: same structure, different function
  • divergent evolution: common ancestry
  • analogous: different structure, same function
  • convergent evolution: similar habitat
  • 1850s: more white moths; 1920: more dark moths

Adaptive radiation

  • adaptive radiation: one point → many habitats
  • Darwin’s finches: seed-eating → insects, plants
  • Australian marsupials: one ancestral stock
  • placental wolf ~ Tasmanian wolf: convergent

Biological evolution

  • Darwin’s key concepts: branching descent, natural selection
  • Lamarck: use and disuse; acquired characters
  • fitness: inherited, genetic basis
  • limited resources + variation: competition

Mechanism of evolution

  • de Vries: evening primrose, mutation
  • saltation: single-step large mutation
  • mutation: random, directionless
  • Darwinian variation (NCERT): small, directional

Hardy–Weinberg principle

  • p + q = 1
  • p + 2pq + q = 1
  • AA = p; Aa = 2pq; aa = q
  • five factors (NCERT): gene flow, drift, mutation, recombination, selection
  • recombination: reshuffles allele combinations (beyond NCERT)
  • stabilising: mean; directional: one side; disruptive: both ends

Modern synthetic theory

  • synthesis: natural selection + Mendelian genetics
  • 5 factors: mutation, recombination, chromosome changes, selection, isolation
  • gene flow and drift also shape populations; hybridisation may add variation
  • isolation: pre-zygotic or post-zygotic
  • allopatric: separated; sympatric: same area

A brief account of evolution

  • first cells: about 2000 mya (NCERT); microbial evidence: at least about 3500 mya
  • jawless fish about 350, plants about 320 mya (NCERT); fossils: about 518 and 470 mya
  • fish-like reptiles: about 200 mya (NCERT)
  • dinosaurs disappeared: about 65 mya (NCERT); modern date: about 66 mya
  • birds: living dinosaurs; coelacanths: tetrapod relatives

Origin and evolution of man

  • 15 mya: ape-like and man-like primates
  • 3–4 mya: upright man-like primates, East Africa
  • first human-like hominid: brain 650–800 cc
  • 1.5 mya: Java fossils, brain about 900 cc
  • Neanderthal man: 1400 cc; 100 000–40 000 years ago
  • cave art: 18 000 years ago; agriculture: 10 000 years ago

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