Read the following passage and answer the questions that follow:
A biology student observes two different organisms under a microscope. In the first organism, the single cell simply splits into two equal halves, with the division occurring in any plane. In the second organism, the cell develops multiple nuclei, and then each nucleus is surrounded by a small amount of cytoplasm to produce many daughter cells simultaneously. The student notes that the first organism has no specific body orientation, whereas a third organism similar to the first shows division only along a specific axis due to a structural feature at one end of its body.
(i) Identify the type of reproduction shown by the first organism and name one example of such an organism. (1 mark)
(ii) What is the mode of reproduction shown by the second organism? Name one example of this organism and state one situation in nature when this mode is particularly advantageous. (1 mark)
(iii) Name the 'structural feature' that causes the third organism to divide along a specific axis and name one organism that shows this. (1 mark)
(iv) All the above are forms of asexual reproduction. State one key difference between asexual and sexual reproduction in terms of the number of parents and genetic variation in offspring. (1 mark)
Generated by claude-sonnet-4-6 · 2026-06-26 01:02 · grounding rag
Model Answer
(i) The first organism shows binary fission. Example: Amoeba (splits into two equal halves in any plane).
(ii) The second organism shows multiple fission. Example: Plasmodium (malarial parasite). It is advantageous during unfavourable conditions (e.g., scarcity of food/water), as many daughter cells are produced at once, improving survival chances.
(iii) The structural feature is the whip-like structure (flagellum) at one end of the cell, which causes division along a definite axis. Organism: Leishmania (causes kala-azar).
(iv) Asexual reproduction requires one parent and produces offspring with no genetic variation (genetically identical). Sexual reproduction requires two parents and produces offspring with greater genetic variation due to combination of DNA from both parents.
Source: Chapter 7, Section 7.2.1 Fission; Section 7.3 Sexual Reproduction
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Explanation
- Binary vs Multiple fission: The key distinction is two daughter cells (any plane) vs many daughter cells simultaneously — examiners expect both features stated clearly.
- Leishmania's flagellum: This is the specific term; "whip-like structure" is also acceptable but naming it as flagellum shows stronger understanding.
- For (iv), examiners award the mark for both contrasting points — number of parents AND genetic variation. Stating only one may lose the mark.
- Always name the organism when asked; a description alone is insufficient for full credit.