(A)_____ affects reproduction in seasonal breeders, both plants and animals

Answer

**Step-by-Step Text Solution:**

1. **Understanding Seasonal Breeders**: Seasonal breeders are organisms that reproduce during specific seasons of the year. Both plants and animals have adapted their reproductive cycles to align with environmental conditions.

2. **Identifying the Key Factor**: The question asks for a factor that affects reproduction in both plants and animals. The key factor here is "photoperiod," which refers to the length of day and night.

3. **Impact on Plants**:
- Plants rely on sunlight for photosynthesis and reproduction.
- The photoperiod influences flowering and fruiting in many plant species.
- Some plants require longer daylight hours (long-day plants) to flower, while others need shorter daylight hours (short-day plants).

4. **Impact on Animals**:
- In animals, the photoperiod affects hormonal changes that regulate reproduction.
- For example, changes in light exposure can influence the secretion of melatonin, a hormone that plays a crucial role in regulating the reproductive cycle in many species.
- This hormonal regulation helps synchronize breeding with favorable environmental conditions.

5. **Conclusion**: The factor that affects reproduction in seasonal breeders, both plants and animals, is the "photoperiod."

**Final Answer**: (A) Photoperiod affects reproduction in seasonal breeders, both plants and animals.

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