Chapter 1: Reproduction in Organisms – Case-Based / Source-Based Questions with Answers
CBSE Class 12 Biology – Case-Based / Source-Based Questions with Answers
Unit I: Reproduction | Chapter 1: Reproduction in Organisms (NCERT Based)
Course & Examination Details
- Course: CBSE Class 12 Biology
- Prescribed By: Central Board of Secondary Education
- Syllabus Reference: NCERT
- Unit: Unit I – Reproduction
- Chapter: Chapter 1 – Reproduction in Organisms
- Exam Relevance: CBSE Class 12 Board Examinations (Competency-Based / Case-Based Questions)
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CBSE Class 12 Biology Chapter 1 Case-Based Questions – Reproduction in Organisms (NCERT)
Section A: Lifespan, Ageing, and Senescence
Case 1
A biologist observed that some insects live only for a few hours, whereas certain trees live for hundreds of years.
Q1. What term is used to describe the duration of life of an organism?
Ans: The duration of life of an organism from birth to natural death is called lifespan.
Q2. Why does lifespan vary among organisms?
Ans: Lifespan varies due to genetic makeup, metabolic rate, body complexity, and environmental adaptability.
Case 2
An old plant shows yellowing of leaves followed by leaf fall before death.
Q3. Identify the biological process involved.
Ans: The process involved is senescence, the final phase of ageing in plants.
Q4. State one significance of senescence in plants.
Ans: Senescence helps in nutrient recycling by transferring nutrients to growing or reproductive parts.
Section B: Types of Reproduction
Case 3
A unicellular organism divides repeatedly to increase its population rapidly under favourable conditions.
Q5. Which type of reproduction is involved?
Ans: Asexual reproduction is involved.
Q6. State one advantage of this type of reproduction.
Ans: It enables rapid multiplication without the need for a mating partner.
Case 4
A population of organisms shows high genetic variation and adaptability to changing environments.
Q7. Which mode of reproduction is responsible for this variation?
Ans: Sexual reproduction is responsible for genetic variation.
Q8. Why is this mode evolutionarily significant?
Ans: It introduces variation, enhancing adaptability and driving evolution.
Section C: Asexual Reproduction
Case 5
A microscopic organism divides into two identical individuals, each capable of independent life.
Q9. Name the process involved.
Ans: The process is binary fission.
Q10. Name one organism showing this process.
Ans: Amoeba shows binary fission.
Case 6
During unfavourable conditions, a protozoan divides its nucleus several times before forming many offspring.
Q11. Identify the reproductive method.
Ans: The method is multiple fission.
Q12. Name the organism commonly showing this process.
Ans: Plasmodium shows multiple fission.
Case 7
A small outgrowth develops on the body of an organism and later separates to form a new individual.
Q13. What is this method of reproduction called?
Ans: This method is called budding.
Q14. Name one organism reproducing by this method.
Ans: Hydra reproduces by budding.
Section D: Vegetative Propagation in Plants
Case 8
A farmer uses stem cuttings to grow identical plants with desirable traits.
Q15. Identify the method of reproduction.
Ans: The method is artificial vegetative propagation.
Q16. State one advantage of this method.
Ans: It preserves desirable traits and ensures uniform crop quality.
Case 9
Potato plants grow from underground stem structures called tubers.
Q17. Name this type of vegetative propagation.
Ans: It is natural vegetative propagation through tubers.
Q18. Why are plants produced genetically identical?
Ans: They arise from mitotic divisions without meiosis, producing clones.
Section E: Sexual Reproduction
Case 10
An organism produces male and female gametes that fuse to form a new individual.
Q19. What type of reproduction is described?
Ans: Sexual reproduction is described.
Q20. Which type of cell division forms these gametes?
Ans: Meiosis forms haploid gametes.
Case 11
In aquatic animals, fertilisation occurs outside the body.
Q21. Name this type of fertilisation.
Ans: This is called external fertilisation.
Q22. Mention one limitation of this type of fertilisation.
Ans: A large number of gametes are wasted, reducing survival chances.
Section F: Events in Sexual Reproduction
Case 12
Formation of gametes and their transfer occur before fusion.
Q23. Name these events collectively.
Ans: These are called pre-fertilisation events.
Q24. Name the two main pre-fertilisation processes.
Ans: Gametogenesis and gamete transfer.
Case 13
After fusion of gametes, a diploid cell undergoes repeated divisions.
Q25. Identify the diploid cell formed after fertilisation.
Ans: The diploid cell is called a zygote.
Section G: Post-Fertilisation Events
Case 14
A zygote develops into an embryo through mitotic divisions and differentiation.
Q26. Name this developmental process.
Ans: The process is called embryogenesis.
Case 15
Some animals lay eggs, while others give birth to young ones.
Q27. Name animals that lay eggs.
Ans: Such animals are called oviparous.
Q28. Name animals that give birth to young ones.
Ans: Such animals are called viviparous.
Section H: Reproductive Health (Basic Concepts)
Case 16
Poor nutrition in organisms leads to reduced reproductive success.
Q29. Which aspect of biology is affected here?
Ans: Reproductive health is affected.
Case 17
Environmental pollution disrupts reproductive processes in animals.
Q30. Mention one way environment affects reproduction.
Ans: Pollution can impair gamete formation and embryonic development.
Section I: Conceptual & Application-Based
Case 18
A population produced through asexual reproduction fails to survive sudden environmental changes.
Q31. Why does this happen?
Ans: Lack of genetic variation makes clones less adaptable to change.
Case 19
Reproductive capacity of organisms decreases in later stages of life.
Q32. Which life phase is responsible for this decline?
Ans: Senescence is responsible for reduced reproductive capacity.
Case 20
Sexually reproducing populations show better survival rates.
Q33. State one reason for better survival.
Ans: Genetic variation improves adaptability and resistance.
Section J: Higher-Order Case Analysis
Case 21
Planaria can regenerate lost parts and form complete organisms.
Q34. Name the biological process involved.
Ans: The process is regeneration.
Case 22
An organism produces identical offspring without fertilisation.
Q35. What term describes such offspring?
Ans: Such offspring are called clones.
Case 23
In flowering plants, pollination ensures transfer of male gametes.
Q36. Under which event is this classified?
Ans: It is a pre-fertilisation event.
Case 24
An embryo develops safely inside the mother’s body.
Q37. Name the type of fertilisation involved.
Ans: Internal fertilisation is involved.
Case 25
A species maintains its population size over generations.
Q38. Which biological process ensures this continuity?
Ans: Reproduction ensures continuity of species.
CBSE Board Exam Note
These Case-Based / Source-Based Questions with Answers are strictly NCERT-aligned, competency-focused, and ideal for CBSE Class 12 Biology board examinations, as per the latest assessment pattern.