Toiduahel

Toiduahel, or food chain, is the sequence of organisms in an ecosystem linked by feeding relationships, through which energy and nutrients flow from one organism to another.

Producers such as plants or algae capture energy via photosynthesis. Primary consumers, usually herbivores, feed on producers. Secondary and higher-level consumers prey on the lower levels. Energy transfer between successive trophic levels is typically around 10%, with the remainder lost as heat or used in metabolism.

In nature, chains are not isolated; many species feed on more than one food source, producing a food web. Detritus-based chains begin with dead organic matter and are sustained by decomposers and detritivores who recycle nutrients.

The length and structure of a food chain are influenced by energy availability and ecosystem constraints; removal or decline of a key species can cause cascading changes; apex predators can regulate populations and maintain diversity.

The concept emerged in early 20th-century ecology, with Charles Elton introducing the food web idea and Lindeman (1942) describing energy transfer and the 10% rule. Common illustrative chains include grass → grasshopper → frog → snake → hawk, and algae → small fish → larger fish.