Chapter 7: Evolution – Very Short Answer Type Questions
CBSE Class 12 Biology Very Short Answer Questions (NCERT): Evolution
Course & Examination Details
- Course: CBSE Class 12 Biology
- Unit: Unit II – Genetics and Evolution
- Chapter: Chapter 7 – Evolution
- Prescribed Textbook: NCERT Biology Class XII
- Examination: CBSE Class 12 Board Examination
- Question Type: Very Short Answer Type (VSA)
- Answer Length: 20–30 words each
Section A: Origin of Life
Q1. What is meant by origin of life?
Answer: Origin of life refers to the process by which living organisms arose from non-living matter on the early Earth.
Q2. Name the theory explaining life originated from chemical substances.
Answer: The theory of chemical evolution explains the origin of life from inorganic and organic molecules.
Q3. Who proposed the theory of chemical evolution?
Answer: A. I. Oparin and J. B. S. Haldane proposed the theory of chemical evolution.
Q4. What type of atmosphere existed on early Earth?
Answer: Early Earth had a reducing atmosphere rich in methane, ammonia, hydrogen, and water vapour.
Q5. What did the Miller–Urey experiment prove?
Answer: It proved that organic molecules like amino acids could be formed abiotically under primitive Earth conditions.
Section B: Evidences for Evolution
Q6. What are homologous organs?
Answer: Homologous organs have the same basic structure and origin but perform different functions, indicating common ancestry.
Q7. Give one example of homologous organs.
Answer: Forelimbs of humans, whales, and bats are homologous organs.
Q8. What are analogous organs?
Answer: Analogous organs have different origin and structure but perform similar functions.
Q9. Give one example of analogous organs.
Answer: Wings of birds and wings of insects are analogous organs.
Q10. What do vestigial organs indicate?
Answer: Vestigial organs indicate evolutionary ancestry and loss of function over time.
Section C: Palaeontological and Molecular Evidence
Q11. What are fossils?
Answer: Fossils are preserved remains or impressions of ancient organisms found in sedimentary rocks.
Q12. Name one connecting link fossil.
Answer: Archaeopteryx is a connecting link between reptiles and birds.
Q13. What does embryological evidence suggest?
Answer: Similarities in early embryonic stages of vertebrates suggest common ancestry.
Q14. How does molecular biology support evolution?
Answer: Similarities in DNA and protein sequences indicate evolutionary relationships among organisms.
Q15. Name a protein used for molecular evolutionary studies.
Answer: Cytochrome c is commonly used to study evolutionary relationships.
Section D: Adaptive Radiation
Q16. What is adaptive radiation?
Answer: Adaptive radiation is the evolution of multiple species from a common ancestor adapted to different environments.
Q17. Name one classic example of adaptive radiation.
Answer: Darwin’s finches of the Galapagos Islands show adaptive radiation.
Q18. Which type of evolution is shown by adaptive radiation?
Answer: Adaptive radiation represents divergent evolution.
Q19. What is divergent evolution?
Answer: Divergent evolution is the development of different species from a common ancestor.
Q20. Give one example of adaptive radiation in mammals.
Answer: Australian marsupials exhibit adaptive radiation.
Section E: Theories of Biological Evolution
Q21. Who proposed the theory of inheritance of acquired characters?
Answer: Jean-Baptiste Lamarck proposed inheritance of acquired characters.
Q22. State Lamarck’s principle of use and disuse.
Answer: Organs used frequently develop, while unused organs degenerate over generations.
Q23. Why is Lamarckism rejected?
Answer: Acquired characters are not inherited, as proved by experimental evidence.
Q24. Who proposed the theory of natural selection?
Answer: Charles Darwin proposed the theory of natural selection.
Q25. What is natural selection?
Answer: Natural selection is the process by which better-adapted organisms survive and reproduce.
Section F: Mechanism of Evolution
Q26. What is mutation?
Answer: Mutation is a sudden heritable change in genetic material that creates new variations.
Q27. What is gene flow?
Answer: Gene flow is the transfer of alleles between populations due to migration.
Q28. What is genetic drift?
Answer: Genetic drift is random change in allele frequencies, significant in small populations.
Q29. Name two types of genetic drift.
Answer: Founder effect and bottleneck effect are types of genetic drift.
Q30. What is recombination?
Answer: Recombination is the formation of new gene combinations during meiosis.
Section G: Hardy–Weinberg Principle
Q31. What does the Hardy–Weinberg principle state?
Answer: Allele frequencies in a population remain constant across generations in the absence of evolutionary forces.
Q32. Write the Hardy–Weinberg equation.
Answer: The equation is p² + 2pq + q² = 1.
Q33. What do p and q represent?
Answer: p and q represent frequencies of dominant and recessive alleles in a population.
Q34. Name one condition for Hardy–Weinberg equilibrium.
Answer: Random mating is essential for maintaining Hardy–Weinberg equilibrium.
Q35. What does deviation from Hardy–Weinberg equilibrium indicate?
Answer: Deviation indicates that evolution is occurring in the population.
Section H: Human Evolution
Q36. What is human evolution?
Answer: Human evolution is the gradual development of modern humans from ancestral primates.
Q37. Name an ape-like ancestor of humans.
Answer: Dryopithecus was an ape-like ancestor of humans.
Q38. Name the earliest tool-using human.
Answer: Homo habilis was the earliest tool-using human.
Q39. Which human ancestor used fire?
Answer: Homo erectus used fire and lived an upright life.
Q40. Name the species to which modern humans belong.
Answer: Modern humans belong to the species Homo sapiens.
Section I: Trends in Human Evolution
Q41. Mention one trend in human evolution.
Answer: Increase in brain size is a major trend in human evolution.
Q42. What change occurred in jaw size during evolution?
Answer: Jaw size gradually reduced with evolution.
Q43. Which continent is considered the cradle of human evolution?
Answer: Africa is considered the cradle of human evolution.
Q44. What evidence supports African origin of humans?
Answer: Fossil and molecular evidence support African origin of humans.
Q45. What is the significance of bipedalism?
Answer: Bipedalism freed forelimbs for tool use and improved vision.
Section J: Integrated Concepts
Q46. What is stabilising selection?
Answer: Stabilising selection favours average individuals and eliminates extreme phenotypes.
Q47. What is directional selection?
Answer: Directional selection favours individuals with traits at one extreme.
Q48. What is disruptive selection?
Answer: Disruptive selection favours both extreme phenotypes over intermediate forms.
Q49. What role does natural selection play in evolution?
Answer: Natural selection drives adaptation and speciation by favouring advantageous traits.
Q50. Why is evolution important in biology?
Answer: Evolution explains the origin, diversity, and adaptation of life on Earth.