The animal in which testis descent into scrotum only during breeding season

Options

A. Frog
B. Kan garoo
C. Shrew
D. Bat.

Answer

To solve the question regarding which animal has testis that descends into the scrotum only during the breeding season, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Testis and Scrotum**:
- The testis is an organ responsible for producing sperm and male hormones.
- The scrotum is a pouch that holds the testis and helps maintain a lower temperature (about 2 degrees Celsius lower than the body temperature) which is essential for sperm production (spermatogenesis).

2. **Identifying the Function of Testis Descent**:
- The descent of the testis into the scrotum is crucial for maintaining the optimal temperature for sperm production.
- In many mammals, the testis descends into the scrotum during specific periods, particularly during breeding seasons.

3. **Analyzing the Options**:
- We have four options: frog, kangaroo, shrew, and bat.
- Frogs do not have a scrotum; they have external fertilization and do not require temperature regulation in the same way.
- Kangaroos have a different reproductive strategy and do not exhibit seasonal testis descent.
- Shrews are small mammals, but they typically do not exhibit this specific behavior.

4. **Identifying the Correct Animal**:
- Bats are known to have testis that descend into the scrotum only during the breeding season. This adaptation allows them to regulate temperature for optimal sperm production during the time they are mating.

5. **Conclusion**:
- Based on the analysis, the correct answer to the question is **bat** (option 4).

### Final Answer:
The animal in which testis descend into the scrotum only during the breeding season is the **bat**.

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