On the rocky sea coasts of Scotland, the larger and competitively superior barnacle Balanus dominates the intertidal area and excludes the smaller barnacle Cathamalus from that zone. Which kind of interaction is being depicted by this example ?

Options

A. Predation
B. Parasitism
C. Commensalism
D. Competition

Explanation

To determine the kind of interaction depicted by the example of the barnacles Balanus and Cathamalus on the rocky sea coasts of Scotland, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Species**: The two barnacle species mentioned are Balanus and Cathamalus. Balanus is described as the larger and competitively superior barnacle, while Cathamalus is the smaller barnacle.

2. **Understand the Competitive Dynamics**: The question states that Balanus dominates the intertidal area and excludes Cathamalus from that zone. This indicates that Balanus is able to outcompete Cathamalus for resources in that habitat.

3. **Define Competition**: In ecology, competition refers to the interaction between organisms where both species are harmed as they vie for the same resources (such as space, food, etc.). In this case, both barnacle species are competing for space on the rocky shore.

4. **Analyze the Impact of Competition**: Since Balanus is competitively superior, it restricts the distribution of Cathamalus. This means that Cathamalus cannot thrive in the same area as Balanus due to the competitive exclusion principle, which states that two species competing for the same resource cannot coexist at constant population values.

5. **Conclude the Type of Interaction**: Given that both species are negatively impacted by their interaction due to competition for limited resources, the interaction depicted in this example is competition.

### Final Answer:
The kind of interaction being depicted by this example is **competition**.

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