Sympatric speciation is caused by

Options

A. Genetic isolation
B. Interbreeding
C. Geographical isolation
D. Reproductive isolation.

Answer

### Step-by-Step Solution:

1. **Understanding Sympatric Speciation**:
- Sympatric speciation is a process where new species arise from a single ancestral species while inhabiting the same geographic region. This means that unlike allopatric speciation, there is no physical barrier separating the populations.

2. **Role of Reproductive Isolation**:
- In sympatric speciation, reproductive isolation occurs within a population. This means that a subpopulation becomes reproductively isolated from the main population, leading to speciation without geographical separation.

3. **Evaluating the Options**:
- The question provides several options to identify what causes sympatric speciation. We need to analyze each option:
- **Genetic Isolation**: This is not a primary factor in sympatric speciation, as it does not involve geographical separation.
- **Embedding**: This refers to mating between closely related individuals, which would not lead to reproductive isolation.
- **Geographical Isolation**: By definition, sympatric speciation does not involve geographical isolation, so this option is incorrect.
- **Reproductive Isolation**: This is the correct answer, as it is the key mechanism that allows a subpopulation to diverge and form a new species while still in the same geographical area.

4. **Conclusion**:
- The primary cause of sympatric speciation is reproductive isolation of subpopulations from their parental population.

### Final Answer:
Sympatric speciation is caused by **reproductive isolation**.