How does the food chain work?
The chain of organisms existing in any natural community, through which energy is transferred, is called a food chain. It involves the transfer of energy from the source in plants through a series of organisms (the sequential interdependence of one trophic level over the others, forms a food chain). Check out Biology Doubts section of Physics Wallah to find more Questions related to Biology.
Food is the common word used to describe the various nutrients that all living heterotrophic organisms must ingest in order to obtain energy and sustain life. A food chain represents the sequence of organisms that are dependent on one another for their source of food. One organism is eaten by another, which is eaten in turn by a third one, and so on. Thus energy is transferred through a series of organisms.
Every predator food chain begins with the autotrophic organisms (mainly the green plants) that constitute producers of the ecosystem. Any organism that cannot produce its own food and depends on another for its nutrition is called a consumer. Every organism unless consumed by another organism ends with the decomposers, the organisms such as bacteria and fungi that degrade the complex organic materials to simple substances, which are reusable by the producers.
The successive levels in the food chains of a community are referred to as trophic levels. Thus, as mentioned earlier all the producers together constitute the first trophic level and the primary consumers (herbivores) constitute the second trophic level. The carnivores dependent on the herbivores constitute the third trophic level. The predators, which depend on the primary carnivores, constitute the secondary carnivores. There are usually four or five trophic levels in food chains. The top-order carnivores are called climax carnivores. The figure 8.12 explains the flow of energy through a typical food chain.
Two types of food chains are present in ecosystems. They are the grazing food chain and the detritus food chain.
Grazing food chain
Grazing animals play an important role in the transfer of energy to the carnivores in this type of food chain, hence the name grazing food chain. Green plants in the terrestrial ecosystems and phytoplankton in the aquatic ecosystems are the producers. The primary consumers are the cattle, sheep, rabbits, deer, insects, and snails which feed on the green plants in the terrestrial ecosystems and the zooplankton, fishes and animals which feed on phytoplankton in the aquatic ecosystems. 20 to 30% of net primary production is consumed by the herbivores. In the soil the unconsumed dead organisms and biological wastes become the food for the detritivores of the detritus food chain. Herbivores (the primary consumers) are eaten by the secondary consumers or primary carnivores. Similarly secondary consumers are eaten by the tertiary consumers or secondary carnivores. Energy flows through these different trophic levels in a grazing food chain. The grazing food chains are linear and are usually with 4 to 5 trophic levels in the chain.