21. Explain how the wing structures of the kiwi bird and the ostrich are different from the wing structure of the eagle. (Hint: Take a look at the bird skeleton pictures and reflect on the size of the wings in each organism.)

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

In general, are there any major differences that you can see? explain

When is your breathing likely to speed up? a. when your white blood cells increase b. when your cells need more energy c. when your heart cells need more carbon dioxide d. when your blood cells have too much oxygen