Which of the following is not dioecious?

Options

A. Ascaris
B. Neries
C. Dentalium
D. Fasciola

Answer

To determine which of the following organisms is not dioecious, we need to understand the definitions of dioecious and monoecious organisms.

### Step-by-Step Solution:

1. **Define Dioecious and Monoecious**:
- Dioecious organisms are those that have distinct male and female individuals. This means that one individual will have only male reproductive organs, while another will have only female reproductive organs.
- Monoecious organisms, on the other hand, possess both male and female reproductive organs within the same individual.

2. **List the Organisms Provided**:
- The organisms mentioned in the question are Ascaris, Nereis, Dentalium, and Fasciola.

3. **Identify the Reproductive Strategy of Each Organism**:
- **Ascaris**: This is a type of roundworm and is known to be dioecious, meaning it has separate male and female individuals.
- **Nereis**: Also a dioecious organism, Nereis is a type of polychaete worm that has distinct male and female individuals.
- **Dentalium**: This organism is classified as dioecious as well, belonging to the class of mollusks.
- **Fasciola**: This is a type of flatworm (specifically a liver fluke) and is classified as monoecious, meaning it has both male and female reproductive organs in the same individual.

4. **Conclusion**:
- Based on the classifications, Fasciola is the organism that is not dioecious, as it possesses both male and female reproductive organs.

### Final Answer:
Fasciola is the organism that is not dioecious.

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