Marchantia is considered heterothallic because it is

Options

A. Heterogametic
B. Bisexual
C. Monoecious
D. Dioecious.

Answer

To determine why Marchantia is considered heterothallic, we can analyze the options provided and understand the definitions related to reproduction in organisms.

### Step-by-Step Solution:

1. **Understanding Heterothallism**:
- Heterothallism refers to a reproductive strategy where an organism has distinct male and female individuals. This leads to cross-fertilization, which increases genetic diversity.

2. **Analyzing the Options**:
- **A. Heterogametic**: This term refers to organisms that produce different types of gametes (e.g., male and female gametes). This does not specifically indicate whether they are from the same or different individuals.
- **B. Bisexual**: This term indicates that an organism has both male and female reproductive structures. This would imply that the organism is capable of self-fertilization, which does not align with heterothallism.
- **C. Monoecious**: Monoecious organisms have both male and female reproductive organs on the same individual. This again does not support the concept of heterothallism.
- **D. Dioecious**: Dioecious organisms have distinct male and female individuals. This means that for reproduction to occur, a male and a female must come together, which aligns with the definition of heterothallism.

3. **Conclusion**:
- Since Marchantia has separate male and female individuals, it is classified as dioecious. This characteristic is what makes it heterothallic, as it relies on cross-fertilization between different individuals for reproduction.

### Final Answer:
Marchantia is considered heterothallic because it is **D. dioecious**.

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