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26-454: The food chain in ecology is a chain of trophic relations. Food chain can refer to the food system , the complex economic and ecological systems that bring food to consumers. Food chain may also refer to: Food chain Food chain studies play an important role in many biological studies. Food chain stability is very important for the survival of most species. When only one element

52-532: A food web , which are non-linear and depict interconnecting pathways of consumption and energy transfer . Food chain models typically predict that communities are controlled by predators at the top and plants ( autotrophs or producers) at the bottom. Thus, the foundation of the food chain typically consists of primary producers . Primary producers, or autotrophs , utilize energy derived from either sunlight or inorganic chemical compounds to create complex organic compounds, such as starch, for energy. Because

78-478: A food chain is a continuous variable providing a measure of the passage of energy and an index of ecological structure that increases through the linkages from the lowest to the highest trophic (feeding) levels. Food chains are directional paths of trophic energy or, equivalently, sequences of links that start with basal species, such as producers or fine organic matter, and end with consumer organisms. Food chains are often used in ecological modeling (such as

104-494: A food chain within said ecosystem. Sea otters, a keystone species in Pacific coastal regions, prey on sea urchins. Without the presence of sea otters, sea urchins practice destructive grazing on kelp populations which contributes to declines in coastal ecosystems within the northern pacific regions. The presence of sea otters controls sea urchin populations and helps maintain kelp forests, which are vital for other species within

130-451: A food chain, except the first organism, are consumers. Secondary consumers eat and obtain energy from primary consumers, tertiary consumers eat and obtain energy from secondary consumers, etc. At the highest trophic level is typically an apex predator , a consumer with no natural predators in the food chain model. When any trophic level dies, detritivores and decomposers consume their organic material for energy and expel nutrients into

156-414: A producer, which is eaten by a primary consumer. The primary consumer may be eaten by a secondary consumer, which in turn may be consumed by a tertiary consumer. The tertiary consumers may sometimes become prey to the top predators known as the quaternary consumers. For example, a food chain might start with a green plant as the producer, which is eaten by a snail, the primary consumer. The snail might then be

182-444: A salad than an animal which ate lettuce. A keystone species is a singular species within an ecosystem that others within the same ecosystem, or the entire ecosystem itself, rely upon. Keystone species' are so vital for an ecosystem that without their presence, an ecosystem could transform or stop existing entirely. One way keystone species impact an ecosystem is through their presence in an ecosystem's food web and, by extension,

208-446: A three-species food chain). They are simplified abstractions of real food webs, but complex in their dynamics and mathematical implications. In its simplest form, the length of a chain is the number of links between a trophic consumer and the base of the web. The mean chain length of an entire web is the arithmetic average of the lengths of all chains in the food web. The food chain is an energy source diagram. The food chain begins with

234-447: Is a pesticide known to biomagnify, which is one of the most significant reasons it was deemed harmful to the environment by the EPA and other organizations. DDT is one of the least soluble chemicals known and accumulates progressively in adipose tissue, and as the fat is consumed by predators, the amounts of DDT biomagnify. A well known example of the harmful effects of DDT biomagnification is

260-465: Is important because the amount of energy transferred decreases as trophic level increases; generally only ten percent of the total energy at one trophic level is passed to the next, as the remainder is used in the metabolic process . There are usually no more than five tropic levels in a food chain. Humans are able to receive more energy by going back a level in the chain and consuming the food before, for example getting more energy per pound from consuming

286-400: Is removed from the food chain it can result in extinction or immense decreases of survival of a species. Many food chains and food webs contain a keystone species , a species that has a large impact on the surrounding environment and that can directly affect the food chain. If a keystone species is removed it can set the entire food chain off balance. The efficiency of a food chain depends on

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312-401: Is the opposite of biomagnification, thus when a pollutant gets smaller in concentration as it progresses up a food web. Many chemicals that bioaccumulate are highly soluble in fats ( lipophilic ) and insoluble in water ( hydrophobic ). For example, though mercury is only present in small amounts in seawater , it is absorbed by algae (generally as methylmercury ). Methylmercury is one of

338-482: The adults, a situation more often seen in aquatic and amphibious environments, e.g., in insects and fishes. This complexity was denominated metaphoetesis by G. E. Hutchinson , 1959. Ecologists have formulated and tested hypotheses regarding the nature of ecological patterns associated with food chain length, such as length increasing with ecosystem volume, limited by the reduction of energy at each successive level, or reflecting habitat type. Food chain length

364-1098: The ban on DDT use in agriculture is testament to the importance of recognizing and responding to biomagnification. Two common groups that are known to biomagnify are chlorinated hydrocarbons , also known as organochlorines, and inorganic compounds like methylmercury or heavy metals . Both are lipophilic and not easily degraded. Novel organic substances like organochlorines are not easily degraded because organisms lack previous exposure and have thus not evolved specific detoxification and excretion mechanisms, as there has been no selection pressure from them. These substances are consequently known as " persistent organic pollutants " or POPs. Metals are not degradable because they are chemical elements . Organisms, particularly those subject to naturally high levels of exposure to metals, have mechanisms to sequester and excrete metals. Problems arise when organisms are exposed to higher concentrations than usual, which they cannot excrete rapidly enough to prevent damage. Persistent heavy metals , such as lead , cadmium , mercury , and arsenic , can have

390-543: The base of the food chain in regions with little to no sunlight. Regardless of where the energy is obtained, a species that produces its own energy lies at the base of the food chain model, and is a critically important part of an ecosystem. Higher trophic levels cannot produce their own energy and so must consume producers or other life that itself consumes producers. In the higher trophic levels lies consumers ( secondary consumers , tertiary consumers , etc.). Consumers are organisms that eat other organisms. All organisms in

416-461: The ecosystem. Biomagnification Biomagnification , also known as bioamplification or biological magnification , is the increase in concentration of a substance, e.g a pesticide, in the tissues of organisms at successively higher levels in a food chain . This increase can occur as a result of: Biological magnification often refers to the process whereby substances such as pesticides or heavy metals work their way into lakes, rivers and

442-458: The energy first consumed by the primary producers. This energy then moves through the trophic levels. Food Chains were first discussed by al-Jahiz , a 10th century Arab philosopher. The modern concepts of food chains and food webs were introduced by Charles Elton . A food chain differs from a food web as a food chain follows a direct linear pathway of consumption and energy transfer. Natural interconnections between food chains make

468-429: The environment in their waste. Decomposers and detritivores break down the organic compounds into simple nutrients that are returned to the soil. These are the simple nutrients that plants require to create organic compounds. It is estimated that there are more than 100,000 different decomposers in existence. Models of trophic levels also often model energy transfer between trophic levels. Primary consumers get energy from

494-724: The most harmful mercury molecules. It is efficiently absorbed, but only very slowly excreted by organisms. Bioaccumulation and bioconcentration result in buildup in the adipose tissue of successive trophic levels: zooplankton , small nekton , larger fish, etc. Anything which eats these fish also consumes the higher level of mercury the fish have accumulated. This process explains why predatory fish such as swordfish and sharks or birds like osprey and eagles have higher concentrations of mercury in their tissue than could be accounted for by direct exposure alone. For example, herring contains mercury at approximately 0.01 parts per million (ppm) and shark contains mercury at greater than 1 ppm. DDT

520-524: The ocean, and then move up the food chain in progressively greater concentrations as they are incorporated into the diet of aquatic organisms such as zooplankton , which in turn are eaten perhaps by fish, which then may be eaten by bigger fish, large birds, animals, or humans. The substances become increasingly concentrated in tissues or internal organs as they move up the chain. Bioaccumulants are substances that increase in concentration in living organisms as they take in contaminated air, water, or food because

546-493: The organic forms of mercury and arsenic do biomagnify in nature. For other contaminants, bioconcentration and bioaccumulation account for their high concentrations in organism tissues. More recently, Gray reached a similar substances remaining in the organisms and not being diluted to non-threatening concentrations. The success of top predatory-bird recovery ( bald eagles , peregrine falcons ) in North America following

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572-399: The prey of a secondary consumer such as a frog, which itself may be eaten by a tertiary consumer such as a snake which in turn may be consumed by an eagle. This simple view of a food chain with fixed trophic levels within a species -species A is eaten by species B, B is eaten by C…- is often contrasted by the real situation in which the juveniles of a species belong to a lower trophic level than

598-449: The producer and pass it to the secondary and tertiary consumers. Food chains are vital in ecotoxicology studies, which trace the pathways and biomagnification of environmental contaminants . It is also necessary to consider interactions amongst different trophic levels to predict community dynamics; food chains are often the base level for theory development of trophic levels and community/ ecosystem investigations. The length of

624-518: The significant decline in North American populations of predatory birds such as bald eagles and peregrine falcons due to DDT caused eggshell thinning in the 1950s. DDT is now a banned substance in many parts of the world. In a review, a large number of studies, Suedel et al. concluded that although biomagnification is probably more limited in occurrence than previously thought, there is good evidence that DDT , DDE , PCBs , toxaphene , and

650-434: The substances are very slowly metabolized or excreted. Although sometimes used interchangeably with " bioaccumulation ", an important distinction is drawn between the two, and with bioconcentration. Thus, bioconcentration and bioaccumulation occur within an organism, and biomagnification occurs across trophic (food chain) levels. Biodilution is also a process that occurs to all trophic levels in an aquatic environment; it

676-564: The sun's light is necessary for photosynthesis , most life could not exist if the sun disappeared. Even so, it has recently been discovered that there are some forms of life, chemotrophs , that appear to gain all their metabolic energy from chemosynthesis driven by hydrothermal vents , thus showing that some life may not require solar energy to thrive. Chemosynthetic bacteria and archaea use hydrogen sulfide and methane from hydrothermal vents and cold seeps as an energy source (just as plants use sunlight) to produce carbohydrates; they form

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