An ecosystem consists of:

  • non-living component of a certain environment, or physical environment and climate-related parameters
  • living component of a certain environment, ie all living organisms
  • system of relationships that links the elements of the various components, or defines the ecological relationships:

Habitat relationship, organism-environment relationship
Trophic relationship, relationship among organisms

Animals to get themselves the necessary nutrients eat plants or other animals that in turn have eaten plants. When an herbivore eats a plant, and then a carnivore eats the herbivore, the sequence of events is called food chain (or trophic sequence).

In a food chain can be distinguished:

  • Producers
  • Primary consumers – herbivores / frugivores
  • Secondary consumers – insectivores and carnivores (predators)

Among the living organisms of an ecosystem can be built numerous food chains. The same organism (producers and consumers) can appear in more chains.
Different animals have often shared food source; this causes competition between them. Numerous predators, occupying the last part of the longest food chains, have a varied diet. The bind of more linear food sequences defines a food network.