Isogamy is found in

Options

A. Hydra
B. Monocystis
C. Plasmodium
D. Planaria

Answer

To determine where isogamy is found, we need to analyze the options provided: hydra, monocystis, plasmodium, and planaria.

### Step-by-Step Solution:

1. **Understand Isogamy**:
- Isogamy refers to the fusion of similar motile gametes. This means that the gametes involved in reproduction are morphologically similar, although they may differ physiologically.

2. **Analyze Each Option**:
- **A. Hydra**:
- Hydra primarily reproduces asexually through budding. It does not exhibit isogamy.
- **B. Monocystis**:
- Monocystis is known to exhibit isogamy. It is an endoparasite of earthworms and has motile gametes that are similar in form.
- **C. Plasmodium**:
- Plasmodium, the causative agent of malaria, undergoes sexual reproduction but does not exhibit isogamy. It has distinct male and female gametes.
- **D. Planaria**:
- Planaria can reproduce sexually and asexually, but it does not exhibit isogamy as it has distinct male and female gametes.

3. **Conclusion**:
- Based on the analysis, the only organism that exhibits isogamy is **Monocystis**. Therefore, the correct answer is **B. Monocystis**.

### Final Answer:
**Isogamy is found in B. Monocystis.**