Which of the following animal groups is entirely aquatic?
a) mollusca
b) crustacea
c) echinodermata
d) arthropoda
e) annelida

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.