An animal that hides under a rock to avoid predators is responding to a(n) stimulus.

The given blank can be filled with External.

The stimulus is a physical entity, which can provoke the response in the body of an organism. The hiding of the organism under the rock in response to the predator is and a type of external stimuli, as in this case, the organisms hide themselves inside the rock in response to the predator, which is present outside the body of the organism.

the fossil record provides evidence of a common ancestor to many species.