The organisms spending most of the time in the transitional area between two communities are called

Options

A. Exotic species
B. Edge species
C. Keystone species
D. Critical link species

Explanation

To solve the question regarding the organisms that spend most of their time in the transitional area between two communities, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Terminology**:
- First, we need to understand what is meant by "transitional area between two communities." This area is known as an **ecotone**.

2. **Identifying Ecotone**:
- An ecotone is a region where two different ecosystems or communities meet and integrate. It often has unique environmental conditions and can support species from both communities as well as unique species that are adapted to the specific conditions of the ecotone.

3. **Identifying the Organisms**:
- The organisms that spend most of their time in this transitional area are referred to as **edge species**. These species thrive in the conditions created by the overlap of two different habitats.

4. **Eliminating Incorrect Options**:
- The options provided include exotic species, age species, keystone species, and critical link species.
- Exotic species are non-native species introduced to an area.
- Keystone species are those that have a disproportionately large effect on their environment relative to their abundance.
- Critical link species are those that play an essential role in the ecosystem but are not a standard term in ecology.

5. **Final Answer**:
- Based on the understanding of the terms and the definitions, the correct answer to the question is **edge species**.

### Final Answer:
**Edge species** are the organisms spending most of their time in the transitional area between two communities.

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