The transfer of energy from organism to organism forms a series called a food chain. All the possible feeding relationships that exist in a biome make up its food web. In lakes and ponds, as elsewhere, the food web consists of producers, consumers, and decomposers. These three types of organisms transfer energy within the biome.

Algae are the primary producers in lakes and ponds. They produce organic materials from inorganic chemicals and outside sources of energy, primarily the Sun.

Animals are consumers. Those that eat only plants, such as snails, are primary consumers in the lake or pond food web. Secondary consumers, such as certain fish, eat the plant-eaters. Tertiary consumers are the predators, like turtles and snakes. Humans fall into the predator category. Humans are also omnivores, organisms that eat both plants and animals.

Decomposers feed on dead, organic matter. These organisms convert...