Q.In a pond ecosystem, the sequence phytoplankton to zooplankton to small fish to large fish is an example of

A food chain is a straight-line sequence of organisms in which each feeds on the one before it. A grazing food chain (GFC) begins with living green plants (e.g. grass to grasshopper to frog to snake to hawk); a detritus food chain (DFC) begins instead with dead organic matter, processed by detritivores and decomposers. The grazing food chain is usually the dominant energy pathway, though the detritus food chain can dominate in some ecosystems, such as densely vegetated wetlands.

In nature, individual food chains rarely stand in isolation, because many consumers, especially omnivores, feed on more than one type of organism and are preyed upon by more than one predator. When multiple grazing and detritus food chains interconnect in this way, the resulting branching network is called a food web, which gives a more realistic picture of feeding relationships than any single chain and confers greater ecological stability, since the loss of one food source does not necessarily starve a consumer that has alternative feeding links.