How did primitive heterotrophs produce energy? A. Aerobic respiration
B. chemical fermentation
C. photosynthesis

as resources become scarce because of population growth, the growth decreases after few years due to lack of resources and food.

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.

the correct answer to this question is #5