All the reproductive methods of living organisms are broadly categorized into two types : 1. Asexual reproduction, and 2. Sexual reproduction.
Asexual reproduction involves the participation of a single parent without the formation of gametes, fertilisation and transfer of genetic material. This method is a common means of rapidly increasing offsprings under favourable conditions.
Generated by claude-sonnet-4-6 · 2026-06-15 06:43 · grounding stimulus
Model Answer
(a) In Leishmania, binary fission occurs in a definite orientation (longitudinal). In Plasmodium, multiple fission (schizogony) occurs.
(b) Sexual reproduction introduces variation in offspring due to combination of genetic material from two parents, which helps in evolution and better adaptability.
(c)
(i) Yeast cells require sugar (glucose) as a nutrient source for energy to carry out budding. Plain water provides no nutrients, so yeast cannot multiply in it.
(ii) Rhizopus (bread mould) requires moisture for spore germination and growth. A dry bread slice lacks sufficient water, so Rhizopus cannot grow on it.
Source: Chapter – How do Organisms Reproduce?, Asexual Reproduction section
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Explanation
- (a): Examiners expect students to distinguish between the two organisms — Leishmania = binary fission (longitudinal), Plasmodium = multiple fission.
- (b): The key phrase is "variation" leading to adaptability/evolution — this is the standard NCERT-expected answer.
- (c)(i) & (ii): Both answers hinge on conditions needed for reproduction — nutrients for yeast and moisture for Rhizopus. Mentioning the specific missing condition is essential for full marks.