Biological Concept of species is mainly based on

Options

A. Morphology and methods of reproduction
B. Methods of reproduction only
C. Morphological features only
D. Reproductive isolation

Answer

### Step-by-Step Solution:

1. **Understanding the Biological Concept of Species**: The biological concept of species refers to a group of organisms that can interbreed and produce fertile offspring. This concept emphasizes the importance of reproduction in defining species.

2. **Identifying Key Terms**: The term "reproductive isolation" is crucial in this context. It refers to mechanisms that prevent different species from interbreeding, thereby maintaining distinct species.

3. **Role of Reproductive Isolation**: Reproductive isolation is responsible for maintaining morphological differences between species. This means that even if two species live in the same area, they will not mate with each other due to various barriers (such as behavioral, temporal, or mechanical barriers).

4. **Evaluating the Options**: The options provided are:
- Morphology and methods of reproduction
- Methods of reproduction only
- Morphological features only
- Reproductive isolation

5. **Selecting the Correct Answer**: According to the biological concept of species as proposed by Mayr, the correct answer is **reproductive isolation**. This is because it is the primary mechanism that defines and maintains the integrity of species.

6. **Conclusion**: Therefore, the biological concept of species is mainly based on reproductive isolation.