*Question*: A change in the environment that causes a response is known as a
*Answer*: stimulus

*Question*: Comparing the skeletons of which of the following fish would best show the evolution of a fish species?
*Answer*: a fish that lived recently and a fish that lived a long time ago

*Question*: What is the smallest unit of an element that still has the properties of that element?
*Answer*:
an atom