The nervous and endocrine systems deal primarily with stimuli. a. intrinsic b. extrinsic c. both a and b d. none of the above

Which statements explains what the fossil records indicates? check all that apply. a) earth is 4.5 billion years old b) many organisms have become extinct c) mammals have always existed on earth d) mass extinctions have occurred several times on earth e) the amount of water on earth has decreased over time?