# Evolution Notes, Class 12 Biology | SwaVid

Evolution: NCERT Class 12 Biology notes with key ideas, key terms, common mistakes and 3 quick checks with worked answers. Written by SwaVid from the textbook.

Canonical: https://www.swavid.com/cbse/class-12/biology/chapter/evolution

Source: https://www.swavid.com/cbse/class-12/biology/chapter/evolution

# Evolution

## Key terms

## Key ideas

## Common mistakes

## Quick checks

## Keep going

## Questions parents ask

## Class 12 Biology on SwaVid

### Origin of life

### Evidences for evolution

### Adaptive radiation

### Mechanism of evolution

### Hardy-Weinberg principle

### Origin and evolution of man

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SwaVid › CBSE › Class 12 › Biology › Evolution

Notes written by SwaVid from the NCERT textbook.

Class 12 Biology, Chapter 6. Key ideas, formulas and common mistakes.

CBSE prints 20 marks for Unit VII, not for this chapter alone.

Short answer. This chapter explains the origin of life and the evolutionary processes that generated biodiversity over geological time. Students learn how natural selection, genetic drift, and reproductive isolation drive changes in populations leading to speciation.

Source: NCERT Biology (Reprint 2026-27) , Chapter 6, Evolution

The Big Bang theory explains the origin of the universe around 20 billion years ago, while Earth formed about 4.5 billion years ago. The Oparin-Haldane hypothesis proposed that life arose from non-living organic molecules, which was supported experimentally by S.L. Miller in 1953.

Fossils provide paleontological evidence of past life forms. Homologous organs indicate common ancestry through divergent evolution, whereas analogous organs result from convergent evolution due to similar selective pressures.

Adaptive radiation is the evolutionary process of different species radiating from a common point into varied geographical or ecological niches. Classic examples include Darwin's finches on the Galapagos Islands and Australian marsupials.

Charles Darwin proposed natural selection acting on minor, continuous variations as the primary mechanism of evolution. Hugo de Vries proposed mutation theory, stating that large, single-step mutations called saltation drive speciation.

Allele frequencies in a large, randomly mating population remain constant from generation to generation in the absence of evolutionary influences. Factors that disrupt this genetic equilibrium include gene flow, genetic drift, mutation, genetic recombination, and natural selection.

Human ancestors progressed through Dryopithecus, Ramapithecus, Australopithecus, Homo habilis, Homo erectus, and Neanderthal man to modern Homo sapiens. Brain capacity increased progressively from 650-800 cc in Homo habilis to about 1400 cc in Neanderthal man.

Try each question first. Then tap it to see the answer.

Given q = 0.4, find p = 1 - q = 1 - 0.4 = 0.6

Heterozygous frequency is given by 2pq

Calculate 2pq = 2 × 0.6 × 0.4 = 0.48

0.48

Identify the reducing gases used: CH₄, H₂, NH₃, and water vapour

Recall the spark discharge temperature produced by electrodes: 800 °C

CH₄, H₂, NH₃, and water vapour at 800 °C

Homo habilis had a brain capacity between 650 and 800 cc

Neanderthal man had a brain capacity of about 1400 cc

650-800 cc and 1400 cc

Human Health and Disease .

Principles of Inheritance and Variation .

Molecular Basis of Inheritance .

Organisms and Populations .

The 13 chapters of Class 12 Biology .

CBSE does not give marks to one chapter. It prints 20 marks for Unit VII, Genetics and Evolution, which includes Evolution.

No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed.

Human Health and Disease.

SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works.

- Ch 6 NCERT book
- 20 marks, Unit VII
- 3 quick checks
- Confusing homologous structures with analogous structures . Remember that homology involves common ancestry with divergent functions, while analogy involves different origins with convergent functions.
- Equating Darwinian variation with de Vriesian mutations . Darwinian variations are small, continuous, and directional, whereas mutations according to de Vries are random, large, and directionless.
- Using p and q as genotype frequencies instead of allele frequencies . Use p and q for the frequencies of individual alleles, while p², 2pq, and q² represent the frequencies of homozygous dominant, heterozygous, and homozygous recessive genotypes.

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