An ecologist is studying the egrets, herons, marsh crabs and marsh grass but not the water or the amount of salt in the water of the salt marsh. What level of ecological organization is he studying? *

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.

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.