Scientist think that all of life on earth originated from which type of organisms?
a. single-cell prokaryotes
b. single-cell eukaryotes
c. multicell animals
d. stromatolites

Which statement describes a way in which the digestive and excretory systems work together? a. the nephrons absorb nutrients from food going to the large intestine. b. the excretory system balances blood gases in the small intestine. c. the intestinal villi filter blood and send wastes to the bladder. d. the excretory system balances the salts and water obtained from digested food