What you will learn in this chapter
- Explain the theories of origin of life, including Oparin–Haldane's idea and Miller's experiment.
- Describe evidences of evolution: fossils, homologous and analogous organs, and natural selection examples (peppered moths and industrial pollution, resistance).
- Explain adaptive radiation and convergent evolution with NCERT examples.
- Compare Darwin's theory of natural selection with de Vries' mutation theory.
- State the Hardy–Weinberg principle and the five factors that disturb genetic equilibrium; explain the three types of natural selection.
- Outline the main stages of human evolution with brain capacities.
📘 Open this chapter on NCERT official website (ncert.nic.in) · The same NCERT chapter is taught in both CBSE and UP Board.
Evolution — Notes
🖼️ Diagrams are now right inside the notes. Tap any picture to zoom and see the name and job of each part; 🧊 3D opens the 3D model.डायग्राम अब नोट्स के अंदर ही हैं। किसी भी चित्र पर टैप करें — ज़ूम करें और हर भाग का नाम व कार्य देखें; 🧊 3D से 3D मॉडल खुलता है।Diagrams ab notes ke andar hi hain. Kisi bhi picture par tap kijiye — zoom kijiye aur har part ka naam aur kaam dekhiye; 🧊 3D se 3D model khulta hai.
Revise these first (prerequisites)
- Chapter 4–5: gene, allele, mutation, variation
- What is a fossil (Class 10 'Heredity' level)
- Basic idea of the adaptations of organisms to their environment
Simple meaning of evolution
Evolution (विकास) = gradual change in organisms over a long period of time, leading to the formation of new types (species). It does not happen in a year or two but over millions of years. All present-day organisms have arisen through gradual change from older organisms.
How did life begin?
Earth was formed about 4.5 billion years ago. Oparin and Haldane proposed that organic molecules first formed from simple chemicals (such as CH₄, NH₃, water) — this is called chemical evolution. Miller tried this in the lab and showed that amino acids could be formed.
Miller's experiment (1953)मिलर का प्रयोग (1953)Miller's experiment (1953)NCERT Fig 6.1Electric sparks in CH₄, NH₃, H₂ and water vapour at 800 °C produced amino acids — support for chemical evolution.800 °C पर CH₄, NH₃, H₂ व जलवाष्प में विद्युत स्पार्क से अमीनो अम्ल बने — रासायनिक विकास का समर्थन।800 °C par CH₄, NH₃, H₂ aur water vapour mein electric spark se amino acids bane — chemical evolution ka support. Where does the evidence come from?
Fossils (जीवाश्म) — remains of ancient organisms buried in rocks — tell us which organisms existed earlier. Comparing the organs of different organisms (e.g., the human arm and the bat's wing) also shows that they had common ancestors.
Homologous organs: vertebrate forelimbsसमजात अंग: कशेरुकियों के अग्रपादHomologous organs: vertebrate forelimbsNCERT Fig 6.3 (b)Same bones (humerus, radius–ulna, carpals) in whale, bat, cheetah and human — different jobs = homologous organs.व्हेल, चमगादड़, चीता और मनुष्य में वही हड्डियाँ (ह्यूमरस, रेडियस–अल्ना, कार्पल) — अलग काम = समजात अंग।Whale, bat, cheetah aur human mein wahi haddiyan (humerus, radius–ulna, carpals) — kaam alag = homologous organs. Natural selection — 'the fit move ahead'
According to Darwin, every population has variations. Individuals that survive better in their environment and produce more offspring pass on their traits, which increase over successive generations. 'Fitness' here does not mean strength; it means reproductive fitness.
A real example: peppered moth
In England, before industrialisation, white moths were more numerous. Pollution turned the tree trunks dark, so white moths became easily visible to birds and were eaten, while dark moths survived. Hence dark moths later became more numerous — a direct example of natural selection.
White- and dark-winged moths (England)सफ़ेद और गहरे पंखों वाले शलभ (इंग्लैंड)White- and dark-winged moths (England)NCERT Fig 6.4Before industrialisation white moths survived on light lichen-covered trees; after soot darkened the trees, dark moths survived more.औद्योगीकरण से पहले हल्के लाइकेन वाले पेड़ों पर सफ़ेद पतंगे बचे; कालिख से पेड़ काले हुए तो काले पतंगे ज़्यादा बचे।Industrialisation se pehle light lichen wale trees par white moths bache; soot se trees kaale hue to dark moths zyada bache. Human evolution
Humans also came about through evolution. From Australopithecines, through Homo habilis, Homo erectus and Neanderthal, to Homo sapiens — the brain (brain capacity) gradually increased. Homo sapiens arose in Africa and spread from there across the world.
Origin and evolution of man (NCERT 6.9)मानव की उत्पत्ति और विकास (NCERT 6.9)Origin and evolution of man (NCERT 6.9)NCERT Section 6.9Read the timeline: Dryopithecus/Ramapithecus → Australopithecines → Homo habilis → Homo erectus → Neanderthal → Homo sapiens.समयरेखा पढ़ें: ड्रायोपिथेकस/रामापिथेकस → ऑस्ट्रेलोपिथेसिन → होमो हैबिलिस → होमो इरेक्टस → निएंडरथल → होमो सेपियंस।Timeline padhiye: Dryopithecus/Ramapithecus → Australopithecines → Homo habilis → Homo erectus → Neanderthal → Homo sapiens.
Quick check ✔
1. According to Darwin, what is the real meaning of 'fitness'?
2. What do fossils tell us?
Basics clear? Now move on to Learn in Detail 👆
As per NCERT 2026-27 — every point you need for the board exam.
Origin of life
The universe is ~13.8 billion years old (Big Bang), the earth ~4.5 billion years. Life appeared ~4 billion years ago. Oparin & Haldane: the first life arose from non-living organic molecules (chemical evolution). Spontaneous generation was disproved by Louis Pasteur.
Miller's experiment (1953)
S.L. Miller passed an electric discharge through CH₄, H₂, NH₃ and water vapour at 800°C → amino acids were formed. This supports chemical evolution.
Miller's experiment (1953)मिलर का प्रयोग (1953)Miller's experiment (1953)NCERT Fig 6.1Electric sparks in CH₄, NH₃, H₂ and water vapour at 800 °C produced amino acids — support for chemical evolution.800 °C पर CH₄, NH₃, H₂ व जलवाष्प में विद्युत स्पार्क से अमीनो अम्ल बने — रासायनिक विकास का समर्थन।800 °C par CH₄, NH₃, H₂ aur water vapour mein electric spark se amino acids bane — chemical evolution ka support. Paleontological evidence
Fossils in rock layers — organisms of different ages; some extinct (e.g., dinosaurs). Life-forms changed over time.
Homologous organs (divergent evolution)
Same structure, different function: forelimbs of whale, bat, cheetah and human; heart, brain. Plants: thorn of Bougainvillea and tendril of Cucurbita.
Homologous organs: vertebrate forelimbsसमजात अंग: कशेरुकियों के अग्रपादHomologous organs: vertebrate forelimbsNCERT Fig 6.3 (b)Same bones (humerus, radius–ulna, carpals) in whale, bat, cheetah and human — different jobs = homologous organs.व्हेल, चमगादड़, चीता और मनुष्य में वही हड्डियाँ (ह्यूमरस, रेडियस–अल्ना, कार्पल) — अलग काम = समजात अंग।Whale, bat, cheetah aur human mein wahi haddiyan (humerus, radius–ulna, carpals) — kaam alag = homologous organs. Analogous organs (convergent evolution)
Different structure, same function: wings of butterfly and bird; eye of octopus and mammal; flippers of penguin and dolphin; sweet potato (root) and potato (stem).
Convergent evolution: placental vs marsupial look-alikesअभिसारी विकास: अपरा स्तनधारी और मार्सुपियल हमशक्लConvergent evolution: placental vs marsupial look-alikesNCERT Fig 6.7Placental mammals and marsupials that look alike (e.g. wolf and Tasmanian wolf) evolved separately — convergent evolution.एक जैसे दिखने वाले अपरा स्तनधारी और शिशुधानी (जैसे भेड़िया और तस्मानियाई भेड़िया) अलग विकसित हुए — अभिसारी विकास।Ek jaise dikhne wale placental mammals aur marsupials (jaise wolf aur Tasmanian wolf) alag-alag bane — convergent evolution. Natural selection – examples
Natural selection in peppered moths (England, effect of industrial pollution on moth colour): in the 1850s, before industrialisation, white-winged moths were more numerous; after industrialisation (1920) dark-winged moths became more numerous. Herbicide/pesticide resistance, antibiotic resistance — evolution due to anthropogenic action.
White- and dark-winged moths (England)सफ़ेद और गहरे पंखों वाले शलभ (इंग्लैंड)White- and dark-winged moths (England)NCERT Fig 6.4Before industrialisation white moths survived on light lichen-covered trees; after soot darkened the trees, dark moths survived more.औद्योगीकरण से पहले हल्के लाइकेन वाले पेड़ों पर सफ़ेद पतंगे बचे; कालिख से पेड़ काले हुए तो काले पतंगे ज़्यादा बचे।Industrialisation se pehle light lichen wale trees par white moths bache; soot se trees kaale hue to dark moths zyada bache. Adaptive radiation
New forms evolving by radiating from one point into different habitats. Darwin's finches (Galapagos), Australian marsupials. Convergent evolution between placental mammals and marsupials.
Darwin's finches — adaptive radiationडार्विन की फिंच — अनुकूली विकिरणDarwin's finches — adaptive radiationNCERT Fig 6.5One ancestral seed-eating finch gave many finches with different beaks for different foods — adaptive radiation.एक पूर्वज बीज-भक्षी फिंच से अलग भोजन के लिए अलग चोंच वाली कई फिंच बनीं — अनुकूली विकिरण।Ek ancestral seed-eating finch se alag khane ke liye alag beak wali kai finches bani — adaptive radiation. Adaptive radiation of Australian marsupialsऑस्ट्रेलियाई मार्सुपियल का अनुकूली विकिरणAdaptive radiation of Australian marsupialsNCERT Fig 6.6From one ancestral marsupial: many Australian marsupials, each fitted to its own habitat — adaptive radiation.एक पूर्वज शिशुधानी से अनेक ऑस्ट्रेलियाई शिशुधानी, हर एक अपने आवास के अनुकूल — अनुकूली विकिरण।Ek ancestral marsupial se bahut se Australian marsupials, har ek apne habitat ke hisaab se — adaptive radiation. Darwin's theory
Branching descent + natural selection. Fitness = reproductive fitness. Alfred Wallace also reached the same conclusion. Lamarck: use and disuse (giraffe's neck) — no longer accepted.
Mutation theory
Hugo de Vries (evening primrose): change through mutation — sudden, large steps (saltation). Darwin's variations were small and directional.
Hardy–Weinberg principle
Allele frequencies in a population remain constant from generation to generation: p² + 2pq + q² = 1. Factors that change them: gene migration / gene flow, genetic drift (founder effect), mutation, genetic recombination, natural selection.
Types of natural selection
Stabilising (more individuals at the mean value), directional (towards one extreme), disruptive (towards both extremes).
Three types of natural selectionप्राकृतिक चयन के तीन प्रकारThree types of natural selectionNCERT Fig 6.8Compare the curves: stabilising keeps the middle, directional shifts to one side, disruptive favours both ends.वक्र मिलाएँ: स्थायीकारी बीच वाले को बचाता है, दिशात्मक एक ओर खिसकाता है, विदारक दोनों सिरों को।Curves compare kijiye: stabilising beech wale ko, directional ek side ko, disruptive dono ends ko favour karta hai. Brief history
Jawless fish ~350 mya; lobefins (coelacanth) → first amphibians; reptiles → dinosaurs; dinosaurs disappeared ~65 mya; mammals expanded.
Human evolution
Dryopithecus, Ramapithecus (~15 mya) → Australopithecines (~2 mya, East Africa) → Homo habilis (first human-like, 650–800 cc, did not eat meat) → Homo erectus (~1.5 mya, 900 cc, ate meat) → Neanderthal (1400 cc, buried their dead) → Homo sapiens (arose in Africa). Agriculture began ~10,000 years ago.
Origin and evolution of man (NCERT 6.9)मानव की उत्पत्ति और विकास (NCERT 6.9)Origin and evolution of man (NCERT 6.9)NCERT Section 6.9Read the timeline: Dryopithecus/Ramapithecus → Australopithecines → Homo habilis → Homo erectus → Neanderthal → Homo sapiens.समयरेखा पढ़ें: ड्रायोपिथेकस/रामापिथेकस → ऑस्ट्रेलोपिथेसिन → होमो हैबिलिस → होमो इरेक्टस → निएंडरथल → होमो सेपियंस।Timeline padhiye: Dryopithecus/Ramapithecus → Australopithecines → Homo habilis → Homo erectus → Neanderthal → Homo sapiens.
The concept in depth — the why and the how. Everything stays within the NCERT syllabus.
Homology vs analogy: which direction of evolution?
Homologous organs (forelimbs of whale, bat, cheetah, human; thorn of Bougainvillea and tendril of Cucurbita) — same structure/origin, different function → divergent evolution and common ancestry. Analogous organs (wings of butterfly and bird; eyes of octopus and mammals; flippers of penguin and dolphin; sweet potato (root) and potato (stem)) — different structure, same function → convergent evolution, due to similar habitat.
Homologous organs: vertebrate forelimbsसमजात अंग: कशेरुकियों के अग्रपादHomologous organs: vertebrate forelimbsNCERT Fig 6.3 (b)Same bones (humerus, radius–ulna, carpals) in whale, bat, cheetah and human — different jobs = homologous organs.व्हेल, चमगादड़, चीता और मनुष्य में वही हड्डियाँ (ह्यूमरस, रेडियस–अल्ना, कार्पल) — अलग काम = समजात अंग।Whale, bat, cheetah aur human mein wahi haddiyan (humerus, radius–ulna, carpals) — kaam alag = homologous organs. Convergent evolution: placental vs marsupial look-alikesअभिसारी विकास: अपरा स्तनधारी और मार्सुपियल हमशक्लConvergent evolution: placental vs marsupial look-alikesNCERT Fig 6.7Placental mammals and marsupials that look alike (e.g. wolf and Tasmanian wolf) evolved separately — convergent evolution.एक जैसे दिखने वाले अपरा स्तनधारी और शिशुधानी (जैसे भेड़िया और तस्मानियाई भेड़िया) अलग विकसित हुए — अभिसारी विकास।Ek jaise dikhne wale placental mammals aur marsupials (jaise wolf aur Tasmanian wolf) alag-alag bane — convergent evolution. Moths and pollution — selection, not mutation
Dark moths were not 'created' after industrialisation; both types of moths already existed. Pollution killed the lichens and tree trunks turned dark, so the environment 'selected' the dark moths. Lichens are indicators of pollution. Similarly, the use of antibiotics/pesticides causes resistant microbes or insects to increase through selection — this is evolution by anthropogenic (human) action, and it links to antibiotics in Chapter 8.
White- and dark-winged moths (England)सफ़ेद और गहरे पंखों वाले शलभ (इंग्लैंड)White- and dark-winged moths (England)NCERT Fig 6.4Before industrialisation white moths survived on light lichen-covered trees; after soot darkened the trees, dark moths survived more.औद्योगीकरण से पहले हल्के लाइकेन वाले पेड़ों पर सफ़ेद पतंगे बचे; कालिख से पेड़ काले हुए तो काले पतंगे ज़्यादा बचे।Industrialisation se pehle light lichen wale trees par white moths bache; soot se trees kaale hue to dark moths zyada bache. Adaptive radiation and convergence together
Many forms evolving from one ancestor in one area for different habitats = adaptive radiation (Darwin's finches; Australian marsupials). Similar forms in Australian marsupials and placental mammals (e.g. marsupial wolf and placental wolf) — two separate adaptive radiations looking alike — is an example of convergent evolution.
Adaptive radiation of Australian marsupialsऑस्ट्रेलियाई मार्सुपियल का अनुकूली विकिरणAdaptive radiation of Australian marsupialsNCERT Fig 6.6From one ancestral marsupial: many Australian marsupials, each fitted to its own habitat — adaptive radiation.एक पूर्वज शिशुधानी से अनेक ऑस्ट्रेलियाई शिशुधानी, हर एक अपने आवास के अनुकूल — अनुकूली विकिरण।Ek ancestral marsupial se bahut se Australian marsupials, har ek apne habitat ke hisaab se — adaptive radiation. Convergent evolution: placental vs marsupial look-alikesअभिसारी विकास: अपरा स्तनधारी और मार्सुपियल हमशक्लConvergent evolution: placental vs marsupial look-alikesNCERT Fig 6.7Placental mammals and marsupials that look alike (e.g. wolf and Tasmanian wolf) evolved separately — convergent evolution.एक जैसे दिखने वाले अपरा स्तनधारी और शिशुधानी (जैसे भेड़िया और तस्मानियाई भेड़िया) अलग विकसित हुए — अभिसारी विकास।Ek jaise dikhne wale placental mammals aur marsupials (jaise wolf aur Tasmanian wolf) alag-alag bane — convergent evolution. Hardy–Weinberg: the 'nothing has changed' equation
In a population, allele frequencies (p, q) remain constant from generation to generation if there is no disturbing factor: p² + 2pq + q² = 1. Five factors disturb the equilibrium: gene migration (gene flow), genetic drift, mutation, genetic recombination and natural selection. If the measured value differs from the equilibrium, it means evolution is taking place. The founder effect is a form of drift in which the allele frequency of a small new population changes.
Three patterns of selection
Stabilising: middle (mean) individuals are favoured → variation decreases. Directional: shift towards one extreme. Disruptive: both extremes are favoured, middle ones decrease → two peaks form. Identify the type from the shape of the curve in the graph.
Three types of natural selectionप्राकृतिक चयन के तीन प्रकारThree types of natural selectionNCERT Fig 6.8Compare the curves: stabilising keeps the middle, directional shifts to one side, disruptive favours both ends.वक्र मिलाएँ: स्थायीकारी बीच वाले को बचाता है, दिशात्मक एक ओर खिसकाता है, विदारक दोनों सिरों को।Curves compare kijiye: stabilising beech wale ko, directional ek side ko, disruptive dono ends ko favour karta hai. Darwin vs de Vries
Darwin: small, directional variations and gradual change. Hugo de Vries, working on evening primrose, proposed that large, sudden variations — mutations — cause evolution; mutations are random and directionless. He called a single-step large mutation saltation. According to the present understanding, variation (mutation + recombination) and natural selection work together.
Common confusions — cleared up
Homologous vs Analogous organs
Homologous: same origin/structure, different function (divergent). Analogous: different origin/structure, same function (convergent).
Lamarck vs Darwin
Lamarck: acquired characters are inherited through use and disuse (giraffe's neck). Darwin: variations already exist; natural selection picks the fit ones from among them.
Genetic drift vs Gene flow
Gene flow = movement of alleles into/out of a population (migration). Genetic drift = change in allele frequency by chance, especially in small populations.
Adaptive radiation vs Convergent evolution
Adaptive radiation: many different forms arise from one ancestor (divergence). Convergent: organisms from different ancestors come to look similar.
Darwin's finches — adaptive radiationडार्विन की फिंच — अनुकूली विकिरणDarwin's finches — adaptive radiationNCERT Fig 6.5One ancestral seed-eating finch gave many finches with different beaks for different foods — adaptive radiation.एक पूर्वज बीज-भक्षी फिंच से अलग भोजन के लिए अलग चोंच वाली कई फिंच बनीं — अनुकूली विकिरण।Ek ancestral seed-eating finch se alag khane ke liye alag beak wali kai finches bani — adaptive radiation.
Video
▶ Evolution Class 12 Biology | Chapter 6 One Shot Animated Video | NCERT + PYQs | Board Exam 2027 · 31 min
1-minute revision Shorts
Diagrams (tap & zoom)
All 8 diagrams of this chapter — tap one to open itइस अध्याय के सभी 8 डायग्राम — खोलने के लिए टैप करेंIs chapter ke saare 8 diagrams — kholne ke liye tap kijiye
Miller's experiment (1953)मिलर का प्रयोग (1953)Fig 6.1
Homologous organs: vertebrate forelimbsसमजात अंग: कशेरुकियों के अग्रपादFig 6.3 (b)
White- and dark-winged moths (England)सफ़ेद और गहरे पंखों वाले शलभ (इंग्लैंड)Fig 6.4
Darwin's finches — adaptive radiationडार्विन की फिंच — अनुकूली विकिरणFig 6.5
Adaptive radiation of Australian marsupialsऑस्ट्रेलियाई मार्सुपियल का अनुकूली विकिरणFig 6.6
Convergent evolution: placental vs marsupial look-alikesअभिसारी विकास: अपरा स्तनधारी और मार्सुपियल हमशक्लFig 6.7
Three types of natural selectionप्राकृतिक चयन के तीन प्रकारFig 6.8
Origin and evolution of man (NCERT 6.9)मानव की उत्पत्ति और विकास (NCERT 6.9)Section 6.9Important questions with answers
Q1. What is the difference between homologous and analogous organs?
Homologous organs have the same basic structure and origin but different functions (e.g., the flipper of a whale and the human hand) — they show divergent evolution. Analogous organs have different structures but the same function (e.g., the wings of a butterfly and a bird) — they show convergent evolution.
Q2. What does the Hardy–Weinberg principle state?
In a large, randomly mating population with no disturbing factors, allele frequencies and genotype frequencies remain constant from generation to generation: p² + 2pq + q² = 1. Gene flow, genetic drift, mutation, recombination and natural selection disturb this equilibrium.
Q3. How did industrial pollution change the colour of moths in England?
In England, before industrialisation, tree trunks were covered with white lichens, so white moths survived. Pollution darkened the trunks, so dark moths stayed hidden from predators and their numbers increased. This is an example of natural selection.
Q4. Give an example of adaptive radiation.
Darwin's finches of the Galapagos — finches with different beaks evolved from one seed-eating finch. Australian marsupials also radiated from one ancestral stock into different habitats.
UP Board previous year questions (2022–2026)
These questions are from real UP Board Intermediate papers (copies from a third-party archive, read and verified by SLH). Also shown: in how many 2022–2026 papers (different sets) a question from this topic appeared. See year-wise papers →
- “Who proposed the theory of 'Natural Selection'? (A) Mendel (B) Lamarck (C) Darwin (D) De Vries”
UP Board 20261 marksQuestions from this topic: 8 papers (2024, 2025, 2026) - “Name the gases which were used by S.L. Miller in the experiment of origin of life.”
UP Board 20261 marksQuestions from this topic: 5 papers (2024, 2025, 2026) - “Distinguish between convergent evolution and divergent evolution.”
UP Board 20263 marksQuestions from this topic: 5 papers (2024, 2026) - “Write an explanatory note on: Hardy-Weinberg principle.”
UP Board 20262.5 marksQuestions from this topic: 5 papers (2024, 2026) - “What is adaptive radiation? Describe it with the help of a suitable example.”
UP Board 20263 marksQuestions from this topic: 5 papers (2024, 2025, 2026) - “What do you understand by: Australopithecines”
UP Board 20243 marksQuestions from this topic: 4 papers (2024) - “What is evolution? Write two evidences of evolution.”
UP Board 20263 marksQuestions from this topic: 3 papers (2025, 2026)
Practice quiz
Tap an option — get instant right/wrong feedback and an explanation. Wrong answers are saved in "My mistakes".
1. What was formed in Miller's experiment?
2. What are the thorn of Bougainvillea and the tendril of Cucurbita?
3. The wings of a butterfly and a bird are examples of which type of evolution?
4. Who proposed the mutation theory?
5. Which is the Hardy–Weinberg equation?
6. Where were Darwin's finches found?
7. Who was the first human-like hominid?
8. Who disproved the theory of spontaneous generation?
Quick revision checklist
Before the exam — try explaining each topic aloud for 1 minute. If you get stuck, reread it in the notes above.
- Origin of life
- Miller's experiment (1953)
- Paleontological evidence
- Homologous organs (divergent evolution)
- Analogous organs (convergent evolution)
- Natural selection – examples
- Adaptive radiation
- Darwin's theory
- Mutation theory
- Hardy–Weinberg principle
- Types of natural selection
- Brief history
- Human evolution