competition drives natural selection, as individual members of a species compete with each other for limited natural resources. The Canada goose and its subspecies may be undergoing , the process of new species forming or becoming distinct. The of horses is comprehensive, and clearly shows the evolution of horses over millions of years.

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