Final answer:
In the experiment with pregnant big brown bats, the treatment group would be composed of the bats that are exposed to different temperatures to understand their preferences or physiological responses.
Step-by-step explanation:
In the context of experiments studying the behavior or physiology of animals, the treatment group typically refers to the subjects that receive the specific condition or variable being tested. For an experiment on temperature selection among pregnant big brown bats, the treatment group would be the bats that are exposed to varying temperatures chosen by the scientists to understand their preferences or physiological responses.
Considering different experiments, for example, those studying yellow buntings with butterflies, or experiments related to fruit flies and their fecundity under different conditions, the treatment groups receive the specific intervention being tested whereas the control group does not but is otherwise managed exactly like the treatment group.
This allows researchers to compare the results and draw conclusions about the effects of the treatment on the behavior or physiology of the subjects in question.