Amensalism is an association between two species where

Options

A. one species is harmed and other is benefitted
B. one species is harmed and other is unaffected
C. one species is benefitted and other is unaffected
D. both the species are harmed

Explanation

### Step-by-Step Solution:

1. **Definition of Amensalism**: Amensalism is a type of ecological interaction between two species where one species is harmed while the other is unaffected. This means that in this relationship, one organism suffers negative effects, while the other organism does not experience any benefit or harm.

2. **Characteristics of Amensalism**:
- One species is negatively impacted (harmed).
- The other species remains neutral (unaffected).
- This relationship does not provide any benefit to the unaffected species.

3. **Example of Amensalism**: A classic example of amensalism is the interaction between penicillin (produced by the mold Penicillium) and bacteria. In this case:
- The Penicillium mold secretes penicillin, which inhibits the growth of bacteria.
- The bacteria are harmed or killed by the presence of penicillin.
- The Penicillium mold is unaffected by the bacteria.

4. **Conclusion**: Amensalism is an important ecological interaction that illustrates how different species can affect each other in various ways. In this case, the harmful effect on one species (the bacteria) occurs without any reciprocal benefit or harm to the other species (the mold).