Chapter 1: Reproduction in Organisms – Short Answer Type Questions

CBSE Class 12 Biology – Short Answer Type 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 Source: NCERT
• Unit: Unit I – Reproduction
• Chapter: Chapter 1 – Reproduction in Organisms
• Exam Relevance: CBSE Class 12 Board Examinations

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CBSE Class 12 Biology Chapter 1 Short Answer Questions – Reproduction in Organisms (NCERT)

Section A: Lifespan, Ageing, and Senescence

Q1. Explain the concept of lifespan in organisms.

Ans: Lifespan refers to the period from birth to natural death of an organism. It is genetically determined and differs among species. Environmental factors like nutrition, climate, and disease resistance may influence lifespan, but each species has a characteristic maximum lifespan.

Q2. Differentiate between ageing and senescence.

Ans: Ageing is a gradual, lifelong process involving decline in physiological efficiency, while senescence is the final phase of ageing marked by severe deterioration of functions. Senescence ultimately leads to death, whereas ageing begins soon after maturity.

Q3. Why do different organisms have different lifespans?

Ans: Lifespan variation occurs due to genetic makeup, metabolic rate, body complexity, and adaptability to environment. Simple organisms generally have shorter lifespans, while complex organisms with better repair mechanisms live longer.

Q4. How is senescence advantageous in population control?

Ans: Senescence removes old and weak individuals from populations, allowing younger, more fit individuals to survive. This helps maintain ecological balance and ensures availability of resources for actively reproducing members.

Q5. Does ageing affect reproductive capacity? Explain.

Ans: Yes, ageing reduces reproductive efficiency due to hormonal imbalance, reduced gamete quality, and decline in physiological functions, eventually leading to reproductive senescence.

Section B: Types of Reproduction

Q6. Define reproduction and state its biological significance.

Ans: Reproduction is the biological process by which organisms produce offspring of their own kind. It ensures continuity of species, maintains population size, and enables transfer of genetic material across generations.

Q7. Compare asexual and sexual reproduction briefly.

Ans: Asexual reproduction involves one parent and produces genetically identical offspring rapidly. Sexual reproduction involves gamete fusion, produces genetic variation, and supports evolution but is relatively slower and energy-intensive.

Q8. Why is sexual reproduction considered evolutionarily important?

Ans: Sexual reproduction introduces genetic variation through meiosis and fertilisation. This variation enhances adaptability to changing environments and forms the basis of natural selection and evolution.

Q9. Name the type of reproduction common in stable environments and justify.

Ans: Asexual reproduction is common in stable environments because it produces identical offspring well-adapted to existing conditions and allows rapid population growth.

Q10. What are clones? How are they formed?

Ans: Clones are genetically identical individuals produced by asexual reproduction. They arise from mitotic divisions without meiosis or fertilisation, maintaining the parent’s genetic makeup.

Section C: Asexual Reproduction

Q11. Explain binary fission with an example.

Ans: Binary fission is asexual reproduction where a unicellular organism divides into two identical daughter cells. In Amoeba, division can occur in any plane, producing two independent organisms.

Q12. Describe multiple fission.

Ans: In multiple fission, the nucleus divides repeatedly, forming many nuclei followed by cytoplasmic division. It occurs in Plasmodium during unfavourable conditions, producing numerous offspring at once.

Q13. What is budding? Explain with an example.

Ans: Budding involves formation of a small outgrowth on the parent body that develops into a new individual. Hydra reproduces by budding under favourable environmental conditions.

Q14. Explain fragmentation as a method of reproduction.

Ans: Fragmentation is asexual reproduction in which the parent organism breaks into fragments, each developing into a new individual. It is common in filamentous algae like Spirogyra.

Q15. What is regeneration? How does it differ from fragmentation?

Ans: Regeneration is the ability to regrow lost body parts, sometimes forming a whole organism. Unlike fragmentation, regeneration primarily serves repair, with reproduction as a secondary outcome.

Section D: Vegetative Propagation in Plants

Q16. Define vegetative propagation.

Ans: Vegetative propagation is asexual reproduction in plants using vegetative parts such as roots, stems, or leaves. It results in genetically identical plants.

Q17. Mention two natural methods of vegetative propagation.

Ans: Natural methods include propagation through tubers like potato and runners like grass, where vegetative structures develop into new plants.

Q18. Describe artificial vegetative propagation.

Ans: Artificial methods include cutting, layering, grafting, and tissue culture. These techniques are used in agriculture to propagate plants with desirable traits rapidly.

Q19. State two advantages of vegetative propagation.

Ans: It ensures rapid multiplication and preserves desirable genetic traits. It is especially useful for seedless plants and plants with poor seed viability.

Q20. Why do farmers prefer vegetative propagation?

Ans: Farmers prefer it because it produces uniform crops, ensures early maturity, and maintains quality traits of high-yielding varieties.

Section E: Sexual Reproduction

Q21. Define sexual reproduction.

Ans: Sexual reproduction involves formation and fusion of male and female gametes, resulting in genetically diverse offspring and contributing to evolution.

Q22. Explain the role of meiosis in sexual reproduction.

Ans: Meiosis produces haploid gametes and introduces genetic variation through crossing over and independent assortment, essential for sexual reproduction.

Q23. What are isogametes and heterogametes?

Ans: Isogametes are morphologically similar gametes, while heterogametes are dissimilar gametes, differing in size or form, as seen in higher organisms.

Q24. Why is sexual reproduction slower than asexual reproduction?

Ans: It involves gametogenesis, mating, and fertilisation, requiring more time and energy compared to direct division in asexual reproduction.

Q25. Name organisms showing external fertilisation.

Ans: Aquatic animals like fishes and frogs show external fertilisation, where gamete fusion occurs outside the body.

Section F: Events in Sexual Reproduction

Q26. What is gametogenesis?

Ans: Gametogenesis is the process of formation of male and female gametes by meiosis in sexually reproducing organisms.

Q27. Explain fertilisation.

Ans: Fertilisation is the fusion of haploid male and female gametes to form a diploid zygote, initiating development of a new organism.

Q28. Distinguish between internal and external fertilisation.

Ans: External fertilisation occurs outside the body, while internal fertilisation occurs inside the female body, offering better protection to developing embryos.

Q29. What is a zygote?

Ans: A zygote is the first diploid cell formed after fertilisation. It undergoes mitotic divisions to develop into an embryo.

Q30. Why is fertilisation essential?

Ans: Fertilisation restores diploid chromosome number and triggers embryonic development, ensuring genetic continuity.

Section G: Post-Fertilisation Events

Q31. Explain embryogenesis.

Ans: Embryogenesis is the development of an embryo from the zygote through mitotic divisions, differentiation, and organ formation.

Q32. What is meant by viviparous organisms?

Ans: Viviparous organisms give birth to young ones after internal development of the embryo, as seen in humans.

Q33. Define oviparous organisms.

Ans: Oviparous organisms lay eggs, and embryonic development occurs outside the mother’s body.

Q34. Why is post-fertilisation development important?

Ans: It ensures growth, differentiation, and formation of functional organs necessary for survival of the organism.

Q35. Which type of cell division occurs after fertilisation?

Ans: Mitotic division occurs after fertilisation, increasing cell number and enabling growth and development.

Section H: Reproductive Health (Basic Concepts)

Q36. What is reproductive health?

Ans: Reproductive health refers to proper functioning of reproductive organs and the ability to produce healthy offspring.

Q37. How does nutrition affect reproductive health?

Ans: Adequate nutrition ensures proper hormonal balance, gamete formation, and successful reproduction.

Q38. Mention environmental factors affecting reproduction.

Ans: Temperature, availability of food, water quality, and pollution can influence reproductive success.

Q39. Why is reproductive health important for species survival?

Ans: It ensures production of viable offspring and maintains population stability.

Q40. Is reproductive health relevant to all organisms? Explain.

Ans: Yes, all reproducing organisms require healthy reproductive systems for successful continuation of species.

Section I: Conceptual & Application-Based

Q41. Why is variation absent in asexual reproduction?

Ans: Asexual reproduction lacks meiosis and fertilisation, producing genetically identical offspring with no variation.

Q42. How does sexual reproduction promote adaptation?

Ans: Genetic variation produced helps organisms adapt to environmental changes, increasing survival chances.

Q43. Why is asexual reproduction common in unicellular organisms?

Ans: It is simple, rapid, and energy-efficient, suitable for unicellular organisms with short life cycles.

Q44. What happens to reproduction during senescence?

Ans: Reproductive capacity declines due to reduced physiological efficiency and hormonal imbalance.

Q45. Why is fertilisation external in aquatic animals?

Ans: Water facilitates movement and fusion of gametes, making external fertilisation effective in aquatic environments.

Section J: Higher-Order Understanding

Q46. Explain the importance of genetic continuity.

Ans: Genetic continuity ensures transfer of hereditary information across generations, maintaining species identity.

Q47. Why are clones disadvantageous in changing environments?

Ans: Lack of variation reduces adaptability, making clones vulnerable to environmental changes.

Q48. How does regeneration differ from reproduction?

Ans: Regeneration mainly repairs body parts, while reproduction produces new individuals.

Q49. Why is sexual reproduction absent in some organisms?

Ans: Simple organisms rely on efficient asexual methods suited to their structure and environment.

Q50. State the overall significance of reproduction.

Ans: Reproduction ensures species survival, genetic continuity, population maintenance, and evolutionary progress.

CBSE Board Exam Note

These Short Answer Type Questions (60–80 words each) are strictly NCERT-based, aligned with CBSE Class 12 Biology board exam standards, and ideal for 2–3 mark questions.