What happens during gas exchange?

a. red blood cells exchange carbon dioxide for oxygen.
b. white blood cells enter the bronchioles.
c. alveoli enter the nuclei of red blood cells.
d. hemoglobin moves from red to white blood cells.

Arafura file snakes are large, aquatic, non-venomous snakes found in the flood-plains of australian rivers. they feed only on fish found in the rivers. it has been observed that heavy rainfall in the wet season in one year leads to prolonged inundation of the floodplains lasting a year or longer. it has also been observed that these snakes remain in good physical condition after a flood. explain how the file snake population in a region is likely to be affected by the prolonged inundation of a flood-plain.

Amino acids contain the elements carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. of the 20 amino acids found in humans, 11 are called "nonessential" because they can be manufactured by the body when needed. which elements in these 11 amino acids are commonly obtained from the metabolism of sugar molecules?

The distant ancestors of tigers may have had bodies without stripes. use the theory of natural selection to explain how tigers may have evolved to have stripes.