Important Questions Class 12 Biology Chapter 6 Evolution

Evolution explains how life forms change across generations through variation, inheritance and selection. Students use this idea to understand fossils, natural selection, adaptive radiation and human ancestry.

Evolution connects origin of life, inheritance, variation and biodiversity into one exam-heavy idea. Important Questions Class 12 Biology Chapter 6 help students practise NCERT-based answers for CBSE 2026 school tests and board-style Biology papers. Chapter 6 covers origin of life, Darwin’s theory, evidences for evolution, adaptive radiation, biological evolution, Hardy-Weinberg principle and human evolution. NCERT defines evolutionary biology as the study of the history of life forms on Earth.

Key Takeaways

• Chapter Identity: Evolution is Chapter 6 in the 2026 NCERT Class 12 Biology syllabus.
• Core Principle: Natural selection favours inherited variations that improve reproductive fitness.
• Equation Focus: Hardy-Weinberg equilibrium uses p² + 2pq + q² = 1 and p + q = 1.
• Evidence Base: Fossils, homology, analogy, molecular similarities and industrial melanism support evolution.

Important Questions Class 12 Biology Chapter 6 Structure 2026

Important Questions Class 12 Biology Chapter 6 for CBSE 2026 Exams

Evolution questions often test definitions, examples and reasoning together. CBSE 2026 papers can frame these ideas as short answers, assertion-reason items and case-based questions.

1. What is evolutionary biology?

Evolutionary biology is the study of the history of life forms on Earth.

1. It studies how organisms originated and changed.
2. It links life forms with geological time.
3. It explains biodiversity through descent, variation and selection.

2. What is evolution?

Evolution is the gradual change in life forms across generations.

1. It produces new forms of life over long periods.
2. It can also explain extinction.
3. It depends on inherited variation and selection.

3. Why is the origin of life called a unique event?

The origin of life is unique because it marks the first appearance of living systems in the universe.

1. Earth formed about 4.5 billion years ago.
2. Life appeared about 500 million years after Earth formed.
3. NCERT places this event in the larger history of the universe.

Origin of Life Class 12 Questions

The origin of life section connects chemistry with biology. Students must know the rejected theories, accepted theory and Miller’s experimental support.

4. What is panspermia?

Panspermia is the idea that life came to Earth from outer space.

1. Early thinkers believed spores moved between planets.
2. Some astronomers still discuss this idea.
3. NCERT mentions it as one proposed explanation for life’s arrival.

5. What was the theory of spontaneous generation?

Spontaneous generation stated that life arose from decaying and rotting matter.

1. People once believed mud, straw and dead matter produced life.
2. This theory lacked experimental support.
3. Louis Pasteur rejected it through controlled experiments.

6. How did Louis Pasteur disprove spontaneous generation?

Pasteur showed that life comes only from pre-existing life.

1. He used pre-sterilised flasks.
2. Life did not arise in sealed sterile conditions.
3. New organisms appeared when killed yeast contacted air.

7. What is chemical evolution?

Chemical evolution means the formation of organic molecules from inorganic substances.

1. It happened before cellular life appeared.
2. Early Earth had high temperature and reducing conditions.
3. Molecules like proteins and RNA could form before life.

8. How did Oparin and Haldane explain the origin of life?

Oparin and Haldane proposed that life arose from non-living organic molecules.

1. Early Earth had methane, ammonia and other reducing gases.
2. Inorganic substances formed organic molecules.
3. These molecules slowly led to the first life forms.

9. What did Miller’s experiment prove?

Miller’s experiment proved that amino acids could form under early Earth-like conditions.

1. Miller used methane, hydrogen, ammonia and water vapour.
2. He passed electric discharge through the gas mixture.
3. Amino acids formed in the apparatus.

10. Why is Miller’s experiment important for Evolution Class 12 Important Questions?

Miller’s experiment supports chemical evolution with laboratory evidence.

1. It recreated early Earth-like conditions.
2. It produced organic compounds from inorganic gases.
3. It strengthened the Oparin-Haldane hypothesis.

11. What were the first non-cellular forms of life?

The first non-cellular forms of life were likely giant molecules.

1. NCERT mentions RNA, proteins and polysaccharides.
2. They may have reproduced their molecules.
3. They appeared before the first cellular forms.

12. When did the first cellular forms of life appear?

The first cellular forms of life appeared about 2000 million years ago.

1. These early cells probably lived in water.
2. Some cells later gained oxygen-releasing ability.
3. They started the long history of biological evolution.

Darwin Theory of Evolution Class 12 Questions

Darwin’s theory explains how natural selection changes populations. The exam focus stays on variation, reproductive fitness and selection.

13. What did Darwin observe during the voyage of H.M.S. Beagle?

Darwin observed that living forms showed similarities with each other and with extinct forms.

1. He studied organisms across different regions.
2. He noticed variation within populations.
3. He concluded that life forms changed gradually.

14. What is natural selection?

Natural selection is the survival and reproduction of better-adapted organisms.

1. Populations contain variations.
2. Some variations help survival in a given environment.
3. Better-adapted organisms leave more progeny.

15. What does fitness mean in Darwin’s theory?

Fitness means reproductive fitness in Darwin’s theory.

1. A fit organism leaves more offspring.
2. Physical strength alone does not define fitness.
3. Nature selects inherited traits that improve reproduction.

16. What are the two key concepts of Darwinian theory?

Branching descent and natural selection are the two key concepts of Darwinian theory.

1. Branching descent explains common ancestry.
2. Natural selection explains survival of favourable variations.
3. Together, they explain evolutionary change.

17. How did Alfred Wallace contribute to evolution theory?

Alfred Wallace reached conclusions similar to Darwin’s natural selection theory.

1. He worked in the Malay Archipelago.
2. He studied variation and adaptation.
3. His work supported natural selection as a mechanism.

18. Why did Darwin reject special creation indirectly?

Darwin’s observations showed gradual evolution instead of fixed creation.

1. Species changed over geological time.
2. Some life forms became extinct.
3. New forms appeared at different periods.

19. How does antibiotic resistance support Darwinian selection?

Antibiotic resistance shows natural selection in bacterial populations.

1. Some bacteria already carry resistance.
2. Antibiotics kill sensitive bacteria.
3. Resistant bacteria survive and multiply.

20. Why does natural selection need heritable variation?

Natural selection needs heritable variation because selected traits must pass to offspring.

1. Non-heritable traits cannot shape future populations.
2. Inherited traits affect survival and reproduction.
3. Evolution changes populations across generations.

Evidence for Evolution Class 12 Questions

Evidence-based questions test fossils, anatomy, morphology and molecular similarities. NCERT uses these examples to show common ancestry and adaptation.

21. How do fossils provide evidence for evolution?

Fossils show that life forms changed across geological time.

1. Fossils occur in sedimentary rocks.
2. Older layers contain older life forms.
3. Different rock ages show different organisms.

22. What is paleontological evidence?

Paleontological evidence is fossil-based evidence for evolution.

1. Fossils represent extinct or ancient organisms.
2. Their position in rocks shows their time period.
3. Fossils help reconstruct evolutionary history.

23. What are homologous organs?

Homologous organs have similar basic structure but different functions.

1. They indicate common ancestry.
2. They show divergent evolution.
3. Mammalian forelimbs are a standard example.

24. Give one animal example of homologous organs.

Forelimbs of humans, whales, bats and cheetahs are homologous organs.

1. They share the same bone pattern.
2. They perform different functions.
3. They include humerus, radius, ulna, carpals, metacarpals and phalanges.

25. Give one plant example of homologous organs.

Thorn of Bougainvillea and tendril of Cucurbita are homologous organs.

1. Both arise from similar plant structures.
2. They perform different functions.
3. They show divergent evolution in plants.

26. What are analogous organs?

Analogous organs perform similar functions but have different origins.

1. They show convergent evolution.
2. Their internal structure differs.
3. Wings of birds and butterflies are examples.

27. Give two examples of analogous organs.

Wings of birds and butterflies and flippers of penguins and dolphins are analogous organs.

1. They perform similar functions.
2. They do not share the same origin.
3. They evolved under similar functional needs.

28. What is industrial melanism?

Industrial melanism is the increase of dark-winged moths in polluted industrial areas.

1. Soot darkened tree trunks after industrialisation.
2. Dark moths gained better camouflage.
3. Predators selected against visible white moths.

29. Why are lichens called pollution indicators?

Lichens are pollution indicators because they do not grow well in polluted air.

1. Clean tree trunks support lichen growth.
2. Industrial pollution reduces lichen growth.
3. Moth camouflage changed when lichens disappeared.

30. How do biochemical similarities support evolution?

Biochemical similarities show shared ancestry among organisms.

1. Similar proteins suggest common origin.
2. Similar genes indicate evolutionary relationships.
3. Molecular evidence supports anatomical evidence.

Adaptive Radiation Class 12 Questions

Adaptive radiation links geography, ancestry and habitat. Students must connect Darwin’s finches and Australian marsupials with this idea.

31. What is adaptive radiation?

Adaptive radiation is the evolution of different species from a common ancestor in one geographical area.

1. It starts from an ancestral stock.
2. It spreads into different habitats.
3. It produces species with different adaptations.

32. Why are Darwin’s finches an example of adaptive radiation?

Darwin’s finches evolved different beaks from a common ancestor.

1. They lived on the Galapagos Islands.
2. Their beaks matched different food habits.
3. Seed-eating forms gave rise to other feeding forms.

33. Why are Australian marsupials important in adaptive radiation?

Australian marsupials show adaptive radiation within an isolated continent.

1. They evolved from an ancestral stock.
2. They adapted to different habitats.
3. They formed many different marsupial types.

34. What is convergent evolution in the Australian example?

Convergent evolution occurs when placental mammals resemble corresponding marsupials.

1. Placental wolf and Tasmanian wolf show this pattern.
2. They evolved similar forms independently.
3. Similar habitats selected similar adaptations.

Biological Evolution Class 12 Important Questions

Biological evolution begins when cellular life gains variation. NCERT links this change with inheritance, fitness and selection.

35. When did biological evolution start in the true sense?

Biological evolution started when cellular life forms with metabolic differences appeared.

1. Cells varied in survival ability.
2. Natural selection acted on these differences.
3. Genetic inheritance made evolution possible.

36. Why do microbes evolve faster than fish or fowl?

Microbes evolve faster because they divide rapidly and produce many generations quickly.

1. Bacteria can multiply within hours.
2. New conditions select resistant variants.
3. Larger animals need much longer generation times.

37. What did Lamarck propose?

Lamarck proposed evolution through use and disuse of organs.

1. He used the giraffe neck as an example.
2. He believed acquired characters passed to offspring.
3. Scientists do not accept this idea in its original form.

38. What did Hugo de Vries propose?

Hugo de Vries proposed that mutations cause evolution.

1. He worked on evening primrose.
2. He supported sudden large changes.
3. He called this process saltation.

39. How does Darwin’s view differ from de Vries’ view?

Darwin saw evolution as gradual, while de Vries saw it as sudden.

1. Darwin focused on small heritable variations.
2. De Vries focused on large mutations.
3. Darwinian evolution happens over many generations.

Hardy Weinberg Principle Class 12 Questions

Hardy-Weinberg questions require clear equations and careful substitution. CBSE students should write genotype frequencies in copy-friendly form.

40. What does Hardy-Weinberg principle state?

Hardy-Weinberg principle states that allele frequencies remain constant across generations.

1. This condition shows genetic equilibrium.
2. It applies when no evolutionary force acts.
3. A change in allele frequency indicates evolution.

41. Write the Hardy-Weinberg equation.

The Hardy-Weinberg equation is p² + 2pq + q² = 1.

1. p represents frequency of allele A.
2. q represents frequency of allele a.
3. The allele frequency equation is p + q = 1.

42. What do p², 2pq and q² represent?

p², 2pq and q² represent genotype frequencies.

1. p² = frequency of AA
2. 2pq = frequency of Aa
3. q² = frequency of aa

43. Which factors disturb Hardy-Weinberg equilibrium?

Five factors disturb Hardy-Weinberg equilibrium.

1. Gene migration or gene flow
2. Genetic drift
3. Mutation
4. Genetic recombination
5. Natural selection

44. What is gene flow?

Gene flow is the movement of genes between populations through migration.

1. New alleles enter one population.
2. Alleles may leave another population.
3. Repeated migration changes gene frequencies.

45. What is genetic drift?

Genetic drift is a random change in allele frequency due to chance.

1. It affects small populations strongly.
2. It can create different allele patterns.
3. It may lead to founder effect.

46. What is founder effect?

Founder effect occurs when a small isolated group forms a new population.

1. The new group carries limited genetic variation.
2. Its allele frequencies may differ from the original population.
3. It can support speciation over generations.

47. Solve a Hardy-Weinberg numerical if q = 0.4.

If q = 0.4, then p = 0.6, p² = 0.36, 2pq = 0.48 and q² = 0.16.

1. Given Data:
   q = 0.4
2. Formula Used:
   p + q = 1
   p² + 2pq + q² = 1
3. Calculation:
   p = 1 - q
   p = 1 - 0.4 = 0.6
   p² = 0.6 × 0.6 = 0.36
   2pq = 2 × 0.6 × 0.4 = 0.48
   q² = 0.4 × 0.4 = 0.16
4. Final Result:
   AA = 0.36, Aa = 0.48, aa = 0.16

Human Evolution Class 12 Biology Important Questions

Human evolution questions often test sequence, brain capacity and key features. NCERT connects these stages with fossils from Africa and Asia.

48. What were Dryopithecus and Ramapithecus?

Dryopithecus and Ramapithecus were primates that lived about 15 million years ago.

1. Dryopithecus was more ape-like.
2. Ramapithecus was more man-like.
3. Both were hairy and walked like apes.

49. What were Australopithecines?

Australopithecines were early human-like primates from East African grasslands.

1. They lived about 2 million years ago.
2. They used stone weapons.
3. They mainly ate fruits.

50. How did Homo habilis, Homo erectus and Neanderthal man differ?

They differed mainly in brain capacity, diet and cultural behaviour.

1. Homo habilis: Brain capacity was 650 to 800 cc. They probably did not eat meat.
2. Homo erectus: Brain capacity was about 900 cc. They probably ate meat.
3. Neanderthal man: Brain capacity was about 1400 cc. They used hides and buried their dead.

Class 12 Biology Chapter 6 Extra Questions

These extra questions match common CBSE 2026 patterns. They revise application-based examples from NCERT Evolution.

51. Why did dinosaurs disappear from Earth?

Dinosaurs disappeared about 65 million years ago, but the exact reason remains uncertain.

1. Some explanations suggest climatic changes.
2. Some suggest many evolved into birds.
3. NCERT states that the truth may lie between these views.

52. How did mammals become dominant after reptiles declined?

Mammals became dominant because they survived and diversified after reptiles declined.

1. Early mammals were small and shrew-like.
2. They protected unborn young inside the mother’s body.
3. They sensed and avoided danger better.

53. Why does evolution not follow a fixed direction?

Evolution does not follow a fixed direction because chance events affect variation and selection.

1. Mutations occur by chance.
2. Genetic drift occurs randomly.
3. Environment selects favourable variations.

54. Can human evolution be called adaptive radiation?

Human evolution is not usually treated as adaptive radiation in NCERT.

1. Adaptive radiation needs many species from one ancestor in one area.
2. Human evolution describes stages within hominin history.
3. It focuses on brain, posture, culture and migration.

55. Why is Bhimbetka important in human evolution?

Bhimbetka shows prehistoric cave art linked with modern humans.

1. NCERT mentions cave art from about 18,000 years ago.
2. Bhimbetka lies in Raisen district of Madhya Pradesh.
3. It reflects early human cultural development.

Case-Based Evolution Class 12 Biology Chapter 6 Questions

Case-based questions check whether students can apply concepts. Read each case carefully before writing the answer.

56. A city used antibiotics heavily. After a few years, doctors found resistant bacteria. Explain the evolutionary process.

This case shows natural selection through antibiotic resistance.

1. Some bacteria had resistant variations.
2. Antibiotics killed sensitive bacteria.
3. Resistant bacteria survived and reproduced.
4. Their frequency increased in the population.
5. Final Answer: Antibiotics acted as a selecting agent.

57. In a polluted industrial region, dark moths increased and white moths reduced. Explain the reason.

This case shows industrial melanism and natural selection.

1. Soot made tree trunks dark.
2. Dark moths gained camouflage.
3. White moths became visible to predators.
4. Dark moths reproduced more successfully.
5. Final Answer: Better camouflage increased dark moth survival.

58. A set of island birds evolved different beaks for different foods. Name and explain the process.

This case shows adaptive radiation.

1. The birds shared a common ancestor.
2. Different food habits selected different beaks.
3. Different forms evolved in the same island region.
4. Final Answer: The process is adaptive radiation.

Assertion-Reason Questions from Evolution Class 12

Assertion-reason questions reward exact logic. Match the reason with the assertion before choosing the answer.

59. Assertion: Fossils provide evidence for evolution. Reason: Fossils occur in rocks of different geological ages.

Both statements are true, and the reason explains the assertion.

1. Fossils show past life forms.
2. Rock layers show time sequence.
3. Different layers contain different organisms.

60. Assertion: Homologous organs indicate common ancestry. Reason: Homologous organs share a similar basic structure.

Both statements are true, and the reason explains the assertion.

1. Homology reflects common origin.
2. Functions may differ.
3. Divergent evolution produces homologous organs.

61. Assertion: Analogous organs show convergent evolution. Reason: Analogous organs have different origins but similar functions.

Both statements are true, and the reason explains the assertion.

1. Different structures can serve the same function.
2. Similar habitats select similar adaptations.
3. Convergent evolution forms analogous organs.

62. Assertion: Hardy-Weinberg equilibrium means no evolution. Reason: Allele frequencies remain constant in genetic equilibrium.

Both statements are true, and the reason explains the assertion.

1. Evolution changes allele frequencies.
2. Equilibrium shows stable allele frequencies.
3. Any deviation indicates evolutionary change.

63. Assertion: Lamarck’s theory is accepted in its original form. Reason: Acquired characters always pass to offspring.

Both statements are false.

1. Lamarck’s original idea lacks acceptance.
2. Acquired characters do not always pass to offspring.
3. Modern evolution uses genetics and selection.

Evolution Class 12 NCERT Questions for Quick Revision

NCERT exercise themes often become school exam questions. Students should practise these answers in direct and concise form.

64. Explain antibiotic resistance in bacteria using Darwinian selection.

Antibiotic resistance occurs because resistant bacteria survive and reproduce.

1. A bacterial population contains variations.
2. Antibiotics kill non-resistant bacteria.
3. Resistant bacteria remain alive.
4. They multiply and pass resistance.
5. Final Answer: Natural selection increases resistant bacteria.

65. Describe one example of adaptive radiation.

Darwin’s finches are a clear example of adaptive radiation.

1. They evolved on Galapagos Islands.
2. Different beaks suited different food sources.
3. Many forms arose from one ancestral stock.

66. Can fossils alone prove every detail of evolution?

Fossils support evolution but do not explain every detail alone.

1. Fossils show past life forms.
2. Some fossil records remain incomplete.
3. Anatomy, biochemistry and genetics also support evolution.

67. Why does homology indicate common ancestry?

Homology indicates common ancestry because structures share the same basic plan.

1. Functions may differ.
2. Origin and structure remain similar.
3. This pattern supports divergent evolution.

68. Why does analogy not prove common ancestry?

Analogy does not prove common ancestry because analogous organs differ in origin.

1. They perform similar functions.
2. Their basic structures differ.
3. They arise through convergent evolution.

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