National League for Nursing (NLN PAX) Practice Exam

What behavior of paramecia is expected if a drop of dilute ammonium hydroxide is introduced?

1. They will swim toward the ammonium hydroxide.

2. They will reproduce rapidly.

3. They will all eventually swim away from the ammonium hydroxide.

4. They will become immobile.

The correct answer is: They will all eventually swim away from the ammonium hydroxide.

Paramecia, like many other unicellular organisms, respond to changes in their environment, particularly the presence of chemicals. When a drop of dilute ammonium hydroxide is introduced, paramecia react negatively to this substance. The expected behavior of paramecia in this scenario is widespread avoidance of the ammonium hydroxide. This is due to ammonia being a substance that can be harmful or toxic to many aquatic microorganisms. The paramecia have sensory structures that allow them to detect chemical changes in their environment, which triggers a behavioral response. As a result, the paramecia will swim away from the area where the ammonium hydroxide is present. While other behaviors such as reproduction or becoming immobile might occur under different contexts or stimuli, they are not the primary response to the introduction of a chemical irritant like ammonium hydroxide. The avoidance reaction is a survival mechanism, allowing the organisms to escape potentially harmful conditions. Thus, the expectation of all paramecia swimming away from the ammonium hydroxide is consistent with their natural behavioral patterns and physiological responses.