Title: key concepts
Course: What can WE do for biodiversity? The European Strategies for habitat conservation > Section: 1_A tale of succes: behind the Iberian lynx tracks

The interaction among organisms aimed at getting food are called feeding or trophic relationships. In an ecosystem, some organisms produce their own food from the non-living environment and some others feed on other organisms. Depending on how they get their food, the organisms of an ecosystem are grouped into trophic levels:

Producers

Autotrophs are the producers in an ecosystem. These organisms take inorganic matter from their environment and produce their own food by using an external energy source. In most ecosystem, producers are typically plants, algae (unicellular and multicellular), or cyanobacteria. These organisms get energy from sunlight and transform inorganic matter – their food – through photosynthesis. Producers are the source of organic matter that, directly or indirectly, will feed all consumers and decomposers

Consumers:

Heterotrophs are the consumers in an ecosystem. These organisms need to feed on other organisms or on the matter these organisms produce.

- Primary consumers are consumers that feed on producers – mostly herbivores, animals that feed on plants.

- Secondary consumers are consumers that feed on primary consumers – mostly carnivores, or omnivores if these animals also feed on producers.

- Tertiary consumers are predators that feed on secondary consumers, while quaternary consumers feed on tertiary consumers, and so on.

Decomposers

Decomposers are heterotrophs that eat the remains and wastes of other organisms: non-living plant matter, excrement, dead animals, etc. Decomposers are essential to all ecosystems: they cause the transformation of organic matter into inorganic or mineral matter. Without this matter, producers wouldn’t be able to produce food. In land ecosystems, decomposers live in the soil. There, the action of tiny invertebrates (earthworms, insects, etc.) on wastes precedes the action by bacteria and fungi, ultimately responsible for the transformation of organic matter into inorganic matter.