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Food chain in a Swedish lake. Osprey feed on northern pike, which in turn feed on perch which eat bleak which eat crustaceans.. A food chain is a linear network of links in a food web, often starting with an autotroph (such as grass or algae), also called a producer, and typically ending at an apex predator (such as grizzly bears or killer whales), detritivore (such as earthworms and woodlice ...
A pyramid of energy or pyramid of productivity shows the production or turnover (the rate at which energy or mass is transferred from one trophic level to the next) of biomass at each trophic level. Instead of showing a single snapshot in time, productivity pyramids show the flow of energy through the food chain. Typical units are grams per ...
Decomposers are often left off food webs, but if included, they mark the end of a food chain. [6] Thus food chains start with primary producers and end with decay and decomposers. Since decomposers recycle nutrients, leaving them so they can be reused by primary producers, they are sometimes regarded as occupying their own trophic level.
In order to more efficiently show the quantity of organisms at each trophic level, these food chains are then organized into trophic pyramids. [1] The arrows in the food chain show that the energy flow is unidirectional, with the head of an arrow indicating the direction of energy flow; energy is lost as heat at each step along the way. [2] [3]
The USDA promoted eight basic food groups prior to 1943, then seven basic food groups until 1956, then four food groups. A food pyramid was introduced in 1992, then MyPyramid in 2005, followed by MyPlate in 2011. Dietary guidelines were introduced in 2015 and slated to be rereleased every five years.
A freshwater aquatic food web. The blue arrows show a complete food chain (algae → daphnia → gizzard shad → largemouth bass → great blue heron). A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community.
Consumer–resource interactions are the core motif of ecological food chains or food webs, [1] and are an umbrella term for a variety of more specialized types of biological species interactions including prey-predator (see predation), host-parasite (see parasitism), plant-herbivore and victim-exploiter systems.