AIPMT Biology Aspirants, read out the next topic AIPMT Biology Study material/ Notes of Ecosystem: Food Chain and Food Web, important for AIPMT Biology.

In ecosystem, energy flows through each trophic level in food chains and webs.

• Food Chain is a sequence of organisms, in which each organism serves as a source of food or energy for the next organism. It shows possible pathway of energy flow among trophic levels in an ecosystem.
• It determines how chemical energy and nutrients move from one organism to another through the trophic levels in an ecosystem.

Food Chain

• Complex network of interconnected food chains is called as food web. As most consumers feed on a variety of different organisms and at multiple trophic levels, food chains are embedded in more complex food webs.

Food Web

• Energy and nutrient flows from one organism to next organism in trophic level, as first is eaten by later. Energy constantly gets lost as heat to the environment during this transfer, but nutrients continue to cycle. Thus, continuous inflow of energy from sun is essential to run the ecosystem.
• Trophic levels are assigned same in food webs just as in food chains.
• Food chains and webs show how producers, consumers, and decomposers are connected to one another as energy flows through trophic levels in an ecosystem.
• Two examples of food chains are Grazing Food Chain(GFC) and a Detrius Food Chain/ Decomposer Food Chain (DFC).

Trophic Levels in Grazing and Detritus Food Chains

• Grazing food chain can be as simple as Grass (Producer) eaten by Goat (Primary Consumer), Goat eaten by Man (Secondary Consumer).
• Detritus food chain (DFC) begins with dead organic matter. It is made up of decomposers which are heterotrophic organisms, mainly fungi and bacteria.
• At the second trophic level, the decomposer food chain has a primary decomposer, which feeds on detritus, rather than a primary consumer.
• At higher trophic levels, the grazing and decomposer food chains often merge. For example, Bird functions as a secondary consumer in the grazing food chain and a tertiary consumer in the decomposer food chain.
• It is common for consumers like humans and birds to feed at multiple trophic levels.

• In an aquatic ecosystem, GFC is the major source of energy flow, while in terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the GFC.
• Detritus food chain may be connected with the grazing food chain at some levels as some of the organisms of DFC are prey to the GFC animals, as we see in figure of Food web, maggots and earthworm of DFC are prey to lizard of GFC.