Generated by claude-sonnet-4-6 · 2026-06-15 06:52 · grounding rag
Model Answer
(a) Sex of offspring is not always genetically determined in all animals. In some animals, environmental factors decide sex:
- Snails – social factors can determine sex.
- Lizards/Turtles – temperature during incubation of eggs determines the sex of offspring.
Thus, factors other than sex chromosomes can determine sex in certain animals.
(b)
| Feature | Female | Male |
|---|---|---|
| Sex chromosomes | XX (two X chromosomes) | XY (one X, one Y chromosome) |
| Gametes produced | All eggs carry X | 50% sperms carry X, 50% carry Y |
The Y chromosome in males is smaller and carries fewer genes than the X chromosome.
Explanation
- Part (a) is 2 marks — give two distinct examples with a brief explanation each. Snails (social/environmental), lizards/turtles (temperature) are standard NCERT examples. The key point is that environmental factors, not genes, determine sex here.
- Part (b) is 1 mark — a simple comparison: Female = XX, Male = XY. One crisp differentiating point is sufficient. Don't over-explain.
- The source passages provided are unrelated (Chemistry/Physics), so this answer is based on NCERT Class 10 Biology (Chapter: Heredity and Evolution), as required by the question.