A(n) is substance in which one or more atoms have the same number of protons (i. e. the same atomic number).

what statement best describes the difference between the sympathetic and parasympathetic nervous systems?

the sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response. the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.

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