What Is a Trophic Level

Food chains show the flow of energy from energy producers to energy consumers in a hierarchy within an ecosystem. The trophic pyramid depicts this energy flow graphically. Within the trophic pyramid, there five trophic levels, each of which represents a group of organisms that obtain energy in the same way. The transfer of energy from organisms that make their own food to those who obtain their energy from consuming other organisms is fundamental to the level hierarchy. These levels make up the trophic pyramid. Trophic Pyramid The trophic pyramid is a graphical way to show the movement of energy throughout the food chain. The amount of available energy decreases as we move up the trophic levels. This process is not the most efficient. It is estimated that only approximately 10% of the energy consumed ends up as biomass as we move up each trophic level. While some organisms (autotrophs) can produce energy, others (heterotrophs) must consume other organisms to meet their energy needs. Trophic levels enable us to see the general energy relationship between different organisms as well as how that energy flows through the food chain. Trophic Levels The first trophic level is composed of algae and plants. Organisms on this level are called producers, as they make their own food by using photosynthesis to convert light energy into chemical energy. These organisms are known as autotrophs. Examples include seaweed, trees, and various plants. The second trophic level is composed of herbivores: animals that eat plants. They are considered primary consumers, since they are the first to eat the producers that make their own food. Examples of herbivores include cows, deer, sheep, and rabbits, all of which consume a variety of plant material. The third trophic level is composed of carnivores and omnivores. Carnivores are animals that eat other animals, while omnivores are animals that eat other animals and plants. This group is considered secondary consumers, since they eat the animals that eat the producers. Examples include snakes and bears. The fourth tropic level is also composed of carnivores and omnivores. Unlike the third level, however, these are animals that eat other carnivores. Therefore, they are known as tertiary consumers. Eagles are tertiary consumers. The fifth trophic level is composed of apex predators. These are animals that do not have natural predators and are thus at the top of the trophic pyramid. Lions and cheetahs are apex predators. When organisms die, other organisms called decomposers consume them and break them down so that the cycle of energy continues. Fungi and bacteria are examples of decomposers. Organisms called detrivores also contribute to this energy cycle. Detrivores are organisms that consume dead organic material. Examples of detrivores include vultures and worms.