National League for Nursing (NLN PAX) Practice Exam

The expected behavior of paramecia in response to a drop of dilute ammonium hydroxide is to swim away from it. Paramecia are single-celled organisms that are sensitive to changes in their environment, particularly the chemical composition of water. Ammonium hydroxide is alkaline and can be harmful or irritating to these organisms.

When exposed to ammonium hydroxide, paramecia would typically react negatively due to the potential toxicity of the alkaline environment. They have the ability to sense chemical gradients in their surroundings and will often move away from harmful substances in what is referred to as a negative chemotactic response. This movement is a survival mechanism, as fleeing from detrimental conditions helps protect them from harm.

In contrast, swimming toward a harmful substance, showing no behavioral change, or all being instantly killed does not accurately depict the typical adaptive response of paramecia to a chemical they perceive as harmful.