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 regarding Ernst Mayr's concept of species, we will analyze each option provided and determine which one aligns with Mayr's definition.

### 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 breed with each other and produce fertile offspring, but they do not breed successfully with members of other species.

2. **Analyzing the Options**:
- **Option A**: "Species is a genetically open system."
- This statement is incorrect because Mayr's concept emphasizes reproductive isolation, meaning species are not genetically open but rather closed systems regarding gene flow with other species.

- **Option B**: "All organisms of a population have a common gene pool."
- This statement is correct. In a population, all organisms share a common gene pool, which consists of all the genetic information available within that population. This aligns with Mayr's definition as it reflects the genetic makeup of a species.

- **Option C**: "Species are interbreeding and interfertile."
- While this statement is partially true, it is somewhat vague. Mayr's definition emphasizes that species are interbreeding and interfertile but also highlights the importance of reproductive isolation from other species.

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

3. **Conclusion**:
- The correct option according to Ernst Mayr's concept of species is **Option B**: "All organisms of a population have a common gene pool."