Read the following and answer the questions:
In a village, a farmer noticed that in his field of sugarcane, all the plants looked almost identical. However, in a nearby herd of cattle that reproduce sexually, significant differences in coat colour, size and horn shape were visible among individuals. The farmer's son, who studies biology, told him that this difference in variation is directly related to the mode of reproduction.
(i) Why do the sugarcane plants in the field show very little variation compared to the cattle? (1 mark)
(ii) What is the primary source of variation in organisms that reproduce asexually? (1 mark)
(iii) Explain how sexual reproduction in cattle generates greater variation than asexual reproduction in sugarcane. (1 mark)
(iv) Why is the presence of variation in the herd of cattle beneficial for the long-term survival of the species? (1 mark)
Generated by claude-sonnet-4-6 · 2026-06-26 01:04 · grounding rag
Model Answer
(i) Sugarcane reproduces asexually (vegetative propagation), producing offspring from a single parent through DNA copying. Since no mixing of genetic material occurs, the plants are nearly identical to each other.
(ii) The primary source of variation in asexually reproducing organisms is errors/inaccuracies during DNA copying (replication).
(iii) In sexual reproduction, genetic material from two different individuals (parents) combines. This mixing produces new combinations of traits, generating greater variation. Asexual reproduction in sugarcane involves only one parent, so offspring inherit identical DNA with minimal variation.
(iv) Variation ensures that if the environment changes drastically (e.g., a new disease or climate change), at least some individuals with favourable traits will survive, preventing the entire species from being wiped out.
Source: Chapter 7, Section 7.1.1 – The Importance of Variation; Chapter 8 – Introduction
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Explanation
- (i) & (iii): The key concept is one parent vs. two parents — asexual reproduction copies one genome; sexual reproduction mixes two, creating diversity.
- (ii): Many students write "mutation" — that is acceptable, but the textbook specifically says variation in asexual reproduction arises from DNA copying errors/inaccuracies.
- (iv): Always link variation → survival during environmental change → stability of the species. This is directly from Section 7.1.1 and is a favourite examiner point.
- Keep each answer to 1–2 lines since each carries only 1 mark.