Which best describes biogeographic isolation

a. it always leads to the formation of new species.

b. it cannot lead to evolution.

c. it is a mechanism for evolution.

d. it occurs only through geographic forces.

(options)

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.