Which of the following defines a population distribution? •The number of members of a population in a glven area
•Statistics that describe a population
•The number of individuals in a population
•The way in which members of a population are dispersed in their environment

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.

and after water is usually warmed by the sun the water temperature raises and then evaporates .

a bird that nests only in a particular tree species.