FIGURE 5.3 The role of energy in a natural system. The amount of energy in a natural system determines which organisms can live in it. (a) A tropical rainforest such as this one in Costa Rica has abundant energy available from the Sun and enough moisture for plants to make use of that energy. (b) Arctic tundra, for example this area in Denali National Park, Alaska, has much less energy available, so plants grow more slowly there and do not reach large sizes. (c) The energy supporting this deep-ocean vent community in the Pacific Ocean comes from chemicals emitted from the vent. Bacteria convert the chemicals into forms of energy that other organisms, such as tube worms, can use.

(a: Steffen Foerster/Shutterstock; b: NancyS/Shutterstock; c: Emory Kristof/National Geographic Stock)