All of the following have an internal skeleton except
a. sand dollars.
b. sand fleas.
c. sea stars.
d. sea lilies.

Mike has a problem with his testosterone. he is unable to produce enough. which will most likely be affected by his inability to produce testosterone? check all that apply.

Penelope studies how the structure and function of the nervous system is related to behavior. she is a psychologist

The large increase in atmospheric carbon dioxide in the last 50 years most likely comes from a. an increase in cellular respiration b. increased decomposition by bacteria c. an increase in the burning of fossil fuels d. an increase in photosynthesis