Food chains, also called food webs, describe the eating relationships between species within an ecosystem An ecosystem is a natural unit consisting of all plants, animals and micro-organisms in an area functioning together with all of the physical (abiotic) factors of the environment. An ecosystem is a unit of interdependent organisms which share the same habitat. Ecosystems usually form a number of food webs which show the interdependence of the or a particular living place. Organisms In biology, an organism is any living thing . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homeostasis as a stable whole. An organism may either be unicellular (single-celled) or be composed of, as in humans, many billions of cells grouped into specialized tissues are connected to the organisms they consume by lines representing the direction of organism or energy transfer. It also shows how the energy In physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law. Eight different forms of energy exist to explain all known natural phenomena. These forms include (but are not limited to) kinetic, potential, thermal, from the producer is given to the consumer A Heterotroph is an organism that uses organic substrates to get its chemical energy for its life cycle. This contrasts with autotrophs such as plants which are able to directly use sources of energy such as light to produce organic substrates from inorganic carbon dioxide. The Cyanobacteria Synechocystis sp. PCC 6803 is an example of an autotroph. Typically a food chain or food web refers to a graph where only connections are recorded, and a food network or ecosystem network refers to a network where the connections are given weights representing the quantity of nutrients or energy being transferred.

Sometimes, on a food chain, each animal is separated with an arrow. If it is pointing right, it means "is eaten by" or "is consumed by".

Organisms represented in food chains

Energy enters the food chain from the sun. Some energy and/or biomass is lost at each stage of the food chain as; faeces (solid waste), movement energy and heat energy (especially by warm-blooded creatures). Therefore, only a small amount of energy and biomass is incorporated into the consumer's body and transferred to the next feeding level, thus showing a Pyramid of Biomass.

Primary producers, commonly forming autotrophs, produce complex organic substances (essentially "food") from an energy source and materials. These organisms are typically photosynthetic Photosynthesis[α] is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria. With the exception of some bacteria, all use water and carbon dioxide as initial substrates and release oxygen as a waste product plants, which use sunlight as their energy source. A few, such as those organisms forming the base of deep-sea vent food webs, are chemotrophic Chemotrophs are organisms that obtain energy by the oxidation of electron donating molecules in their environments. These molecules can be organic or inorganic (lithotrophs). The chemotroph designation is in contrast to phototrophs which utilize solar energy. Chemotrophs can be either autotrophic or heterotrophic, using chemical energy instead. Organisms that get their energy by organic substances are called heterotrophs. Heterotrophs include herbivores Herbivory is a form of predation in which an organism, known as a herbivore, consumes principally autotrophs such as plants, algae and photosynthesizing bacteria. By that definition, many fungi, some bacteria, many animals, some protists and a small number of parasitic plants can be considered herbivores. However, herbivory is generally restricted, which obtain their energy by consuming live plants Plants are living organisms belonging to the kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. About 350,000 species of plants, defined as seed plants, bryophytes, ferns and fern allies, are estimated to exist currently. As of 2004, some 287,655 species had been; carnivores A carnivore , meaning 'meat eater' (Latin carne meaning 'flesh' and vorare meaning 'to devour'), is an animal that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of vertebrate and/or invertebrate animal tissue, whether through predation or scavenging. Animals that depend solely on animal flesh for their, which obtain energy from eating live animals Animals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and independently. Most animals are also. Ultimately detritivores Detritivores, also known as detritus feeders or saprophages, are heterotrophs that obtain nutrients by consuming detritus . By doing so, they contribute to decomposition and the nutrient cycles, scavengers and decomposers Decomposers are organisms that consume dead or decaying organisms, and, in doing so, carry out the natural process of decomposition. Like herbivores and predators, decomposers are heterotrophic, meaning that they use organic substrates to get their energy, carbon and nutrients for growth and development. Decomposers use deceased organisms and non- may predate living or consume dead biomass.

An animal which eats plants is a herbivore.An animal which eats other animals is a carnivore.An animal which eats plants and other animals is an omnivore. Food webs are more detailed then food chains

Flow of food chains

A food chain is the flow of energy from one organism to the next and to the next and so on. Organisms in a food chain are grouped into trophic levels In ecology, trophic dynamics is the system of trophic levels , which describe the position that an organism occupies in a food chain — what an organism eats, and what eats the organism, based on how many links they are removed from the primary producers Primary producers are those organisms in an ecosystem that produce biomass from inorganic compounds . In almost all cases these are photosynthetically active organisms (plants, cyanobacteria and a number of other unicellular organisms; see article on photosynthesis). However, there are examples of archea (unicellular organisms) that produce. Trophic levels In ecology, trophic dynamics is the system of trophic levels , which describe the position that an organism occupies in a food chain — what an organism eats, and what eats the organism may contain either a single species or a group of species that are presumed to share both predators and prey. They usually start with a plant and end with a carnivore. The diagram below is a food chain from a Swedish lake. Osprey The Osprey , sometimes known as the sea hawk, is a diurnal, fish-eating bird of prey. It is a large raptor, reaching 60 centimeters (24 in) in length with a 1.8 metre (6 ft) wingspan. It is brown on the upperparts and predominantly greyish on the head and underparts, with a black eye patch and wings feed on northern pike The northern pike , Esox lucius, is a species of carnivorous fish of the genus Esox (the pikes). They are typical of brackish and freshwaters of the northern hemisphere (i.e. holarctic in distribution). They are also known by the literal translation of their Latin name, "water wolf" that feed on perch Perca is the genus of fish referred to as perch or, sometimes, yellow perch, a group of freshwater fish belonging to the family Percidae. Perch, of which there are three species in different geographical areas, lend their name to a large order of vertebrates: the Perciformes, from the Greek perke meaning perch, and the Latin forma meaning shape that eat bleak that feed on freshwater shrimp Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important food source for larger animals from fish to whales. Though unshown, the primary producers of this food chain are probably autotrophic phytoplankton Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words phyton, or "plant", and πλαγκτος , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high enough numbers, they may. Phytoplankton and algae Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds. They are photosynthetic, like plants, and "simple" because they lack the many distinct organs found in land plants. For that reason they are form the base of most freshwater food chains. It is often the case that biomass Biomass, as a renewable energy source, refers to living and recently dead biological material that can be used as fuel or for industrial production. In this context, biomass is commonly plant matter grown to generate electricity or produce heat. For example, forest residues , yard clippings and wood chips may be used as biofuel. However, biomass of each trophic level In ecology, trophic dynamics is the system of trophic levels , which describe the position that an organism occupies in a food chain — what an organism eats, and what eats the organism decreases from the base of the chain to the top. This is because energy is lost to the environment with each transfer. On average, only 10% of the organism's energy is passed on to its predator. The other 90% is used for the organism's life processes or it is lost as heat to the environment. Graphic representations of the biomass or productivity at each tropic level are called trophic pyramids An ecological pyramid is a graphical representation designed to show the biomass or productivity at each trophic level in a given ecosystem. Biomass pyramids show the abundance or biomass of organisms at each trophic level, while productivity pyramids show the production or turnover in biomass. Ecological pyramids begin with producers on the. In this food chain for example, the biomass of osprey is smaller than the biomass of pike, which is smaller than the biomass of perch. Some producers, especially phytoplankton, are so productive and have such a high turnover rate that they can actually support a larger biomass of grazers. This is called an inverted pyramid, and can occur when consumers live longer and grow more slowly than the organisms they consume. In this food chain, the productivity of phytoplankton is much greater than that of the zooplankton consuming them. The biomass of the phytoplankton, however, may actually be less than that of the copepods. Directly linked to this are pyramids of numbers, which show that as the chain is traveled along, the number of consumers at each level drops very significantly, so that a single top consumer (e.g. a Polar Bear The polar bear is a bear native to the Arctic Ocean and its surrounding seas. It is the world's largest carnivore species found on land. It's also the largest bear, together with the omnivore Kodiak bear which is approximately the same size, but which is a subspecies of the brown bear that is normally smaller than the polar bear. An adult male) will be supported by literally millions of separate producers (e.g. Phytoplankton Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words phyton, or "plant", and πλαγκτος , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high enough numbers, they may). There are many types of food chains or(webs)depending on the certain habitat or environment.

Food web

A food web extends the food chain concept from a simple linear pathway to a complex network of interactions.

Food chains are overly simplistic as representatives of what typically happens in nature. The food chain shows only one pathway of energy and material transfer. Most consumers feed on multiple species and are, in turn, fed upon by multiple other species. The relations of detritivores and parasites are seldom adequately characterized in such chains as well. The food chain has a producer, consumer, herbivore, carnivore, omnivore, decomposer.

A food web is a set of interconnected food chains by which energy and materials circulate within an ecosystem (see Ecology Ecology is the interdisciplinary scientific study of the distribution and abundance of organisms and their interactions with their environment. The environment of an organism includes all external factors, including abiotic ones such as climate and geology, and biotic factors, including members of the same species (conspecifics) and other species). The food web is divided into two broad categories: the grazing web, which typically begins with green plants, algae, or photosynthesizing plankton, and the detrital web, which begins with organic debris. These webs are made up of individual food chains. In a grazing web, materials typically pass from plants to plant eaters (herbivores) to flesh eaters (carnivores). In a detrital web, materials pass from plant and animal matter to bacteria and fungi (decomposers), then to detrital feeders (detritivores), and then to their predators (carnivores).

Generally, many interconnections exist within food webs. For example, the fungi that decompose matter in a detrital web may sprout mushrooms that are consumed by squirrels, mice, and deer in a grazing web. Robins are omnivores, that is, consumers of both plants and animals, and thus are in both detrital and grazing webs. Robins typically feed on earthworms, which are detritivores that feed upon decaying leaves.

Herbivores Herbivory is a form of predation in which an organism, known as a herbivore, consumes principally autotrophs such as plants, algae and photosynthesizing bacteria. By that definition, many fungi, some bacteria, many animals, some protists and a small number of parasitic plants can be considered herbivores. However, herbivory is generally restricted, consumers of green plants, belong to the second trophic level. Carnivores, predators feeding upon the herbivores, belong to the third. Omnivores, consumers of both plants and animals, belong to the second and third. Secondary carnivores, which are predators that feed on predators, belong to the fourth trophic level. As the trophic levels rise, the predators become fewer, larger, fiercer, and more agile. At the second and higher levels, decomposers of the available materials function as herbivores or carnivores depending on whether their food is plant or animal material.

III Energy Flow Through these series of steps of eating and being eaten, energy flows from one trophic level to another. Green plants or other photosynthesizing organisms use light energy from the sun to manufacture carbohydrates for their own needs. Most of this chemical energy is processed in metabolism and dissipated as heat in respiration. Plants convert the remaining energy to biomass, both above ground as woody and herbaceous tissue and below ground as roots. Ultimately, this material, which is stored energy, is transferred to the second trophic level, which comprises grazing herbivores, decomposers, and detrital feeders. Most of the energy assimilated at the second trophic level is again lost as heat in respiration; a fraction becomes new biomass. Organisms in each trophic level pass on as biomass much less energy than they receive. Thus, the more steps between producer and final consumer, the less energy remains available. Seldom are there more than four links, or five levels, in a food web. Eventually, all energy flowing through the trophic levels is dissipated as heat Heat is the transfer of thermal energy between two bodies which are at different temperatures. The SI unit for heat is the joule. The process whereby energy loses its capacity to do work is called entropy.

The earliest food webs were published by Victor Summerhayes and Charles Elton Charles Sutherland Elton was an English zoologist and animal ecologist. His name is associated with the establishment of modern population and community ecology, including studies of invasive organisms in 1923 and Hardy in 1924. Summerhayes and Elton's Charles Sutherland Elton was an English zoologist and animal ecologist. His name is associated with the establishment of modern population and community ecology, including studies of invasive organisms (above) depicted the interactions of plants Plants are living organisms belonging to the kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. About 350,000 species of plants, defined as seed plants, bryophytes, ferns and fern allies, are estimated to exist currently. As of 2004, some 287,655 species had been, animals Animals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and independently. Most animals are also and bacteria The bacteria [bækˈtɪərɪə] (singular: bacterium)[α] are a large group of unicellular microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals. Bacteria are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste, water, and deep on Bear Island, Norway Norway (pronounced /ˈnɔɹweɪ/ ; Norwegian: Norge (Bokmål) or Noreg (Nynorsk)), officially the Kingdom of Norway, is a country in Northern Europe occupying the western portion of the Scandinavian Peninsula, as well as Jan Mayen and the Arctic archipelago of Svalbard under the Spitsbergen Treaty. The majority of the country shares a border to.^[1]

The direct steps as shown in the food chain example above seldom reflect reality. This web makes it possible to show much bigger animals (like a seal) eating very small organisms (like plankton). Food sources of most species in an ecosystem are much more diverse, resulting in a complex web of relationships as shown in the figure on the right. In this figure, the grouping of Algae Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds. They are photosynthetic, like plants, and "simple" because they lack the many distinct organs found in land plants. For that reason they are → Protozoa While there is no exact definition of the term "protozoan", most scientists use the word to refer to a unicellular heterotrophic protist, such as an amoeba or a ciliate. The term algae is used for microorganisms that photosynthesize. However, the distinction between protozoa and algae is often vague. For example, the alga Dinobryon has → Oligochaeta Oligochaeta is a subclass in the biological phylum Annelida and includes various earthworms. Specifically, it contains the terrestrial megadrile earthworms (some of which are semi- or fully aquatic), and freshwater or semi-terrestrial microdrile forms including the tubificids, pot worms and ice worms (Enchytraeidae), blackworms (Lumbriculidae) and → Northern Eider Eiders are large seaducks in the genus Somateria. Steller's Eider, despite its name, is in a different genus → Arctic Fox The Arctic Fox , also known as the White Fox or Snow Fox, is a small fox native to cold Arctic regions of the Northern Hemisphere and is common throughout the Arctic tundra biome. Although it is often assigned to its own genus Alopex, the definitive mammal taxonomy list, as well as genetic evidence places it in Vulpes with the majority of the is a chain; the whole complex network is a food web.

See also

• Balance of Nature The Balance of nature refers to the theory that ecological systems are usually in a stable equilibrium, which is to say that a small change in some particular parameter (the size of a particular population, for example) will be corrected by some negative feedback that will bring the parameter back to its original "point of balance" with
• Biodiversity Biodiversity is the variation of life forms within a given ecosystem, biome, or for the entire Earth. Biodiversity is often used as a measure of the health of biological systems. The biodiversity found on Earth today consists of many millions of distinct biological species, which is the product of nearly 3.5 billion years of evolution
• Ecology Ecology is the interdisciplinary scientific study of the distribution and abundance of organisms and their interactions with their environment. The environment of an organism includes all external factors, including abiotic ones such as climate and geology, and biotic factors, including members of the same species (conspecifics) and other species
• Ecosystem An ecosystem is a natural unit consisting of all plants, animals and micro-organisms in an area functioning together with all of the physical (abiotic) factors of the environment. An ecosystem is a unit of interdependent organisms which share the same habitat. Ecosystems usually form a number of food webs which show the interdependence of the
• Earth Science Earth science , is an all-embracing term for the sciences related to the planet Earth. It is arguably a special case in planetary science, the Earth being the only known life-bearing planet. There are both reductionist and holistic approaches to Earth science. There are four major disciplines in earth sciences, namely geography, geology,
• Food supply chains
• Food systems The term "food system" is used frequently in discussions about nutrition, food, health, community economic development and agriculture. A food system includes all processes involved in feeding a population: growing, harvesting, processing, packaging, transporting, marketing, consumption, and disposal of food and food-related items. It
• Natural environment The natural environment, commonly referred to simply as the environment, is a term that encompasses all living and non-living things occurring naturally on Earth or some region thereof
• Nature Nature, in the broadest sense, is equivalent to the natural world, physical world or material world. "Nature" refers to the phenomena of the physical world, and also to life in general. It ranges in scale from the subatomic to the cosmic
• List of feeding behaviours Feeding is the process by which organisms, typically animals, obtain food. Terminology often uses either the suffix -vore from Latin vorare, meaning 'to devour', or phagy, from Greek φαγειν, meaning 'to eat'
• Antipredator adaptations Antipredator adaptations are evolutionary adaptations developed over time, which assist prey organisms in their constant struggle against their predators. There are several ways antipredator adaptations can be classified, such as behavioral or non-behavioral or by taxonomic groups

References

Notes

1. ^ Summerhayes VS, Elton CS (1923) Contributions to the Ecology of Spitsbergen and Bear Island. Interactions of herring Herring are small, oily fish of the genus Clupea found in the shallow, temperate waters of the North Pacific and the North Atlantic, including the Baltic Sea. Two species of Clupea are currently recognized, the Atlantic herring and the Pacific herring (Clupea pallasii), each of which may be divided into subspecies. Herrings are forage fish which and plankton Plankton consist of any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. Plankton are defined by their ecological niche rather than their phylogenetic or taxonomic classification. They provide a crucial source of food to more familiar aquatic organisms such as fish in the North Sea

Bibliography

• "Food chain" A Dictionary of Zoology. Ed. Michael Allaby. Oxford University Press, 1999. Oxford Reference Online. Oxford University Press. University of Utah. 22 November 2007 [http://www.oxfordreference.com/views/ENTRY.html?subview=Main&entry=t8.e3348

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