USA Biology Olympiad (USABO) Practice Exam

What is the best example of habituation in organisms?

1. Birds learning new songs

2. Hydra initially contracting when touched, but stopping afterwards

3. Frogs adapting to seasonal changes

4. Trees losing leaves in winter

The correct answer is: Hydra initially contracting when touched, but stopping afterwards

Habituation is a form of learning in which an organism decreases or ceases its response to a stimulus after repeated exposure to that stimulus. The best example of this concept is observed in the hydra. Initially, when a hydra is touched, it contracts as a reflexive response, but with continued or repeated touches, it learns to ignore the stimulus and no longer contracts. This demonstrates how the hydra has adapted its behavior to distinguish between harmful and non-harmful stimuli, reflecting a clear example of habituation. The other examples, while involving some form of learning or adaptation, do not exemplify habituation in the same way. Birds learning new songs involves more complex cognitive processing and is not a straightforward case of reduced responsiveness to a repeated stimulus. Frogs adapting to seasonal changes pertains to physiological and behavioral adjustments to environmental factors rather than repeated exposure to a specific stimulus. Trees losing leaves in the winter is a seasonal adaptation responding to environmental conditions rather than a learned behavior following repeated exposure.