Isogamy takes place in

Options

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

Answer

To determine where isogamy takes place, we need to analyze the given options based on the definition and characteristics of isogamy.

### Step-by-Step Solution:

1. **Understand Isogamy**:
- Isogamy is a form of sexual reproduction that involves the fusion of gametes that are similar in size and shape. This typically occurs in many unicellular organisms.

2. **Evaluate the Options**:
- **Option A: Plasmodium**:
- Plasmodium reproduces both sexually and asexually. It has distinct male and female gametocytes, which means the gametes are not similar in morphology. Therefore, this option is not isogamous.

- **Option B: Hydra**:
- Hydra primarily reproduces asexually through budding. There is no fusion of gametes involved in this process, so it does not represent isogamy.

- **Option C: Monocystis**:
- Monocystis is a parasite that has isogamous gametes. The gametes can unite to form a zygote, which is characteristic of isogamy. This option fits the definition.

- **Option D: Planaria**:
- Planaria reproduce asexually through regeneration. They do not have isogamous gametes, as they do not engage in the fusion of similar gametes.

3. **Conclusion**:
- Based on the analysis, the correct answer is **Monocystis** (Option C), as it is the organism where isogamy takes place.

### Final Answer:
Isogamy takes place in **Monocystis**.