A process in which the fitness of one species is significantly decreased in the presence of another species is

Options

A. mutualism
B. proto-cooperation
C. competition
D. commensalism

Answer

To solve the question, "A process in which the fitness of one species is significantly decreased in the presence of another species is," we need to analyze the options provided and understand the definitions of each term.

### Step-by-Step Solution:

1. **Understanding the Question**: The question is asking for a biological interaction where one species suffers a decrease in fitness due to the presence of another species.

2. **Analyzing the Options**:
- **A. Mutualism**: This is a type of interaction where both species benefit from each other. Therefore, it does not fit the description of one species' fitness decreasing.
- **B. Protocorporation**: This is a form of mutualism where both species benefit, but their survival is not dependent on each other. Again, this does not fit the description.
- **C. Competition**: This is an interaction where two species compete for limited resources (like food or territory). In this scenario, the fitness of the weaker species decreases in the presence of the stronger species. This fits the description perfectly.
- **D. Commensalism**: In this interaction, one species benefits while the other is neither helped nor harmed. This does not match the question's requirement of decreased fitness.

3. **Conclusion**: Based on the analysis, the correct answer is **C. Competition**. This is because competition leads to a decrease in the fitness of one species due to the presence of another species competing for the same resources.

### Final Answer:
C. Competition