(a) List three distinguishing features between sexual and asexual types of reproduction. (b) Explain why variations are observed in the offsprings of sexually reproducing organisms?
(a) List three distinguishing features between sexual and asexual types of reproduction. (b) Explain why variations are observed in the offsprings of sexually reproducing organisms?
(a) Distinguishing features between Asexual and Sexual Reproduction:
| Feature | Asexual Reproduction | Sexual Reproduction |
|---|---|---|
| Number of Parents | Involves only a single parent. | Involves two parents (male and female). |
| Gamete Formation | No gametes (germ-cells) are formed or fused. | Involves the formation and fusion of male and female gametes. |
| Genetic Variation | Offspring are genetically identical or highly similar to the parent (clones). | Offspring show significant genetic variations due to mixing of parental DNA. |
(b) Why variations are observed in the offspring of sexually reproducing organisms:
- Inaccuracies in DNA Copying: The biochemical reactions involved in copying DNA during cell division are not accurate. These minor copying errors introduce subtle variations.
- Combination of DNA from Two Parents: In sexual reproduction, DNA from two different individuals (each with their own unique set of accumulated variations from previous generations) is combined. This mixing of two distinct genomes creates a completely novel and unique combination of traits in the offspring, greatly accelerating the rate of variation.
Marking Scheme
- 1Three correct distinguishing features between asexual and sexual reproduction (0.5 mark each): 1.5 Marks
- 2Explanation of variations due to DNA copying errors (0.75 mark) and combination of DNA from two parents (0.75 mark): 1.5 Marks
Hint
For part (a), compare the number of parents, involvement of gametes, and variation levels. For part (b), think about DNA copying errors and the effect of combining DNA from two different individuals.
Quick Oral Answer
Asexual reproduction involves one parent and no gametes, while sexual reproduction involves two parents and gamete fusion. Variations occur in sexual reproduction because DNA from two different parents is combined, along with minor copying errors.
Analysis & Explanation
Asexual reproduction relies solely on mitosis, meaning offspring inherit DNA from a single source, limiting variation to rare copying errors. Sexual reproduction involves meiosis (which shuffles genes) and fertilisation (which combines two different genetic blueprints), resulting in unique offspring.
Common Mistakes
- 1Writing that asexual reproduction has absolutely zero variation (some variation exists due to DNA copying errors).
- 2Confusing the terms 'gamete' and 'zygote'.
Interesting Facts
Because sexual reproduction combines DNA from two individuals, every single human being (except identical twins) has a completely unique DNA sequence that has never existed before in the history of the earth!
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2013?
This question carries 3 marks in the CBSE Class 10 Science 2013 examination.
Which chapter does this question come from in Science?
This question is from the chapter "How do Organisms Reproduce?" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Asexual vs Sexual Reproduction & Significance of Variation" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2013 paper?
This is a Short Answer question from Section A in the CBSE Class 10 Science 2013 paper.