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A food web model is a network of food chains. Each food chain starts with a primary producer or autotroph, an organism, such as an alga or a plant, which is able to manufacture its own food. Next in the chain is an organism that feeds on the primary producer, and the chain continues in this way as a string of successive predators.
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 ...
The number of trophic links per consumer is a measure of food web connectance. Food chains are nested within the trophic links of food webs. Food chains are linear (noncyclic) feeding pathways that trace monophagous consumers from a base species up to the top consumer, which is usually a larger predatory carnivore. [8] [9] [10]
Trophic cascades are powerful indirect interactions that can control entire ecosystems, occurring when a trophic level in a food web is suppressed. For example, a top-down cascade will occur if predators are effective enough in predation to reduce the abundance, or alter the behavior of their prey, thereby releasing the next lower trophic level from predation (or herbivory if the intermediate ...
A diagram that sets out the intricate network of intersecting and overlapping food chains for an ecosystem is called its food web. [6] 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.
The tiny marine cyanobacterium Prochlorococcus, discovered in 1986, forms today part of the base of the ocean food chain and accounts for more than half the photosynthesis of the open ocean [23] and an estimated 20% of the oxygen in the Earth's atmosphere. [24]
The pelagic food web, showing the central involvement of marine microorganisms in how the ocean imports carbon and then exports it back to the atmosphere and ocean floor The biological pump (or ocean carbon biological pump or marine biological carbon pump ) is the ocean's biologically driven sequestration of carbon from the atmosphere and land ...
The strength of bottom-up controls on energy flow are determined by the nutritional quality, size, and growth rates of primary producers in an ecosystem. [ 14 ] [ 22 ] Photosynthetic material is typically rich in nitrogen (N) and phosphorus (P) and supplements the high herbivore demand for N and P across all ecosystems. [ 26 ]