Trophic levels

Organisms occupy hierarchical positions in an ecosystem related to the way they obtain energy. It's important to note that every trophic level receives less energy than the level below it, so they need to eat more in order to get enough energy.

The trophic levels mainly go as follows:

Producers

Plants such as grass, and some plankton, are producers, the first trophic level. They create organic food molecules by using inorganic molecules from the surroundings and energy from the sun. Turn chemical energy into energy usable by other organisms. Also called autotrophs or "self-feeders" because they don't need to eat any organism.

First level consumers (herbivores)

First level consumers, such as moose, fish and cows, eat the producers. Along with other consumers, they're called heterotrophs because they eat other organisms. The energy they get from the plants is less than the original energy produced by them.

Second and third level consumers (carnivores)

Second and third level consumers eat other consumers. As they're a high trophic level, they get a very small amount of the original energy that their prey obtained from producers, so they need to have more food. Also called heterotrophs.

Decomposers or saprobes

Decomposers, such as bacteria or fungi, break down dead or decaying organisms in a process called decomposition. In this process, nutrients are returned to the soil to be used by producers, so the cycle completes.