Which of the following is correct, according to Ernst Mayr's concept of species?

Options

A. Species is a genetically open system
B. All organisms of a population have a common gene pool
C. Species are inter-breeding and inter-fertile
D. Two species are not reproductively isolated

Answer

To solve the question about Ernst Mayr's concept of species, let's analyze each option based on his definition of species.

### Step-by-Step Solution:

1. **Understanding Ernst Mayr's Concept of Species**:
- Ernst Mayr defined a species as a group of interbreeding natural populations that are reproductively isolated from other such groups. This means that members of a species can mate and produce fertile offspring, while they are isolated from other species in terms of reproduction.

2. **Analyzing the Options**:
- **Option A**: "Species is a genetically open system."
- This is incorrect. Mayr's concept emphasizes reproductive isolation, which implies that species are not genetically open systems but rather closed systems in terms of gene flow with other species.

- **Option B**: "All organisms of a population have a common gene pool."
- This is correct. According to Mayr, all individuals within a species share a common gene pool, which is the sum of all genetic information available in that population.

- **Option C**: "Species are interbreeding and interfertile."
- This is partially correct but misleading. While species are interbreeding, the term "interfertile" suggests that they can breed with any other species, which is not true according to Mayr's definition. Species are interbreeding but are reproductively isolated from other species.

- **Option D**: "Two species are not reproductively isolated."
- This is incorrect. Mayr's concept emphasizes that species are reproductively isolated from one another, which is a key aspect of his definition.

3. **Conclusion**:
- Based on the analysis, the correct answer according to Ernst Mayr's concept of species is **Option B**: "All organisms of a population have a common gene pool."