Spirogyra reproduces by fragmentation, while Rhizopus reproduces by spore formation. (a) What is the key advantage spore formation has over fragmentation when environmental conditions become unfavourable? (b) Why can neither of these asexual methods work effectively for reproduction in complex multicellular animals?
Generated by claude-sonnet-4-6 · 2026-06-26 01:04 · grounding rag
Model Answer
(a) Spores are covered by thick protective walls that help them survive unfavourable conditions (lack of moisture, heat, etc.). When conditions improve, they germinate and grow into new individuals. Fragmentation, by contrast, offers no such protection — exposed fragments cannot withstand harsh environments.
(b) Complex multicellular animals have specialised cells organised into tissues and organs placed at definite positions in the body. Simple cell-by-cell division (fragmentation) or single-cell spore formation cannot regenerate this organised body plan, making these asexual methods impractical for such organisms.
Source: Chapter 7, sections 7.2.2 Fragmentation and 7.2.6 Spore Formation
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Explanation
- Part (a) is worth ~1 mark: the key word examiners look for is "thick-walled spores" surviving unfavourable conditions — don't just say "spores are better," explain why (protective walls).
- Part (b) is worth ~2 marks: the textbook's exact logic is that complex organisms have cells organised into tissues → organs → definite positions, so neither simple fragmentation nor spore formation can reconstruct that complexity. Use the textbook phrasing ("specialised cells," "tissues," "organs") for full credit.
- Avoid generic statements like "they are too big" — the examiner wants the organisational complexity argument directly from the passage.