Senility is unhealthy state of Paramecium in which overall activities of the animalcule be- come sluggish and Paramecium is likely to die. It is due to

Options

A. repeated conjugation
B. repeated binary fission
C. repeated endomixis
D. repeated autogamy

Answer

To solve the question regarding the unhealthy state of Paramecium known as senility, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Senility**:
- Senility refers to a decline in physical and mental functions, typically associated with aging. In the context of Paramecium, it indicates a state where the organism's activities become sluggish, leading to a higher risk of death.

2. **Identifying the Cause**:
- The question asks for the reason behind senility in Paramecium. We need to analyze the options provided: repeated conjugation, repeated binary fission, repeated endomixes, and repeated autogamy.

3. **Analyzing Reproductive Methods**:
- **Repeated Binary Fission**: This is the primary asexual reproduction method in Paramecium, where the organism divides into two. Over time, excessive binary fission can lead to a decline in vitality and sluggishness, contributing to senility.
- **Repeated Conjugation**: This is a sexual reproduction process involving the temporary union of two Paramecium organisms. It does not lead to senility but rather promotes genetic diversity.
- **Repeated Endomixes**: This involves internal nuclear reorganization and does not directly cause senility.
- **Repeated Autogamy**: This is a form of self-fertilization that occurs under certain conditions, such as starvation, but it is not the primary cause of senility.

4. **Conclusion**:
- After analyzing all the options, the most likely cause of senility in Paramecium is **repeated binary fission**. This process, when repeated excessively, leads to a decline in the organism's overall health and activity.

### Final Answer:
The unhealthy state of senility in Paramecium is due to **repeated binary fission**.

---