Reproductive isolation is

Options

A. Inability to interbreed
B. Ability to interbreed
C. Breeding in isolation
D. Intraspecific breeding

Answer

### Step-by-Step Text Solution:

1. **Definition of Reproductive Isolation (RI)**:
- Reproductive Isolation refers to the inability of a species to breed successfully with related species. This means that even if two species are closely related, they cannot produce viable offspring together.

2. **Understanding the Inability**:
- The term emphasizes "inability," which indicates that reproductive isolation is not about the ability to breed, but rather the barriers that prevent successful breeding.

3. **Causes of Reproductive Isolation**:
- There are various factors that contribute to reproductive isolation, including:
- **Geographical Barriers**: Physical separation of species due to geographical features like mountains, rivers, or distances.
- **Behavioral Differences**: Variations in mating rituals or behaviors that prevent species from recognizing each other as potential mates.
- **Genetic Barriers**: Differences in genetic makeup that lead to incompatibility in reproduction.

4. **Analysis of Options**:
- The question provides multiple options regarding the definition of reproductive isolation.
- **Intraspecific Breeding**: This refers to breeding within the same species, which does not define reproductive isolation.
- **Breeding in Isolation**: This does not accurately describe reproductive isolation as it does not specify the inability to breed with related species.
- **Ability to Interbreed**: This is incorrect since reproductive isolation is about the inability to interbreed.

5. **Conclusion**:
- The correct understanding of reproductive isolation is that it is the inability of a species to breed successfully with related species due to various differences.