ecosystem ecosystem an ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact.: 458 these biotic and abiotic components are linked together through nutrient cycles and energy flows. energy enters the system through photosynthesis and is incorporated into plant tissue. by feeding on plants and on one another, animals play an important role in the movement of matter and energy through the system. they also influence the quantity of plant and microbial biomass present. by breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and microbes. left: coral reef ecosystems are highly productive marine systems. right: temperate rainforest, a terrestrial ecosystem. part of a series onbiologyscience of life index outline glossary history (timeline) key components cell theory ecosystem evolution phylogeny properties of life adaptation energy processing growth order regulation reproduction response to environment domains and kingdoms of life archaea bacteria eukarya (animals, fungi, plants, protists) branches anatomy biotechnology botany cell biology ecology evolutionary biology genetics marine biology microbiology molecular biology mycology neuroscience paleontology phycology physiology protistology virology zoology research biologist (list) list of biology awards list of journals list of research methods list of unsolved problems applications agricultural science biomedical sciences health technology pharming biology portal category ecosystems are controlled by external and internal factors. external factors such as climate, parent material which forms the soil and topography, control the overall structure of an ecosystem but are not themselves influenced by the ecosystem. internal factors are controlled, for example, by decomposition, root competition, shading, disturbance, succession, and the types of species present. while the resource inputs are generally controlled by external processes, the availability of these resources within the ecosystem is controlled by internal factors. therefore, internal factors not only control ecosystem processes but are also controlled by them. ecosystems are dynamic entities—they are subject to periodic disturbances and are always in the process of recovering from some past disturbance. the tendency of an ecosystem to remain close to its equilibrium state, despite that disturbance, is termed its resistance. the capacity of a system to absorb disturbance and reorganize while undergoing change so as to retain essentially the same function, structure, identity, and feedbacks is termed its ecological resilience. ecosystems can be studied through a variety of approaches—theoretical studies, studies monitoring specific ecosystems over long periods of time, those that look at differences between ecosystems to elucidate how they work and direct manipulative experimentation. biomes are general classes or categories of ecosystems. however, there is no clear distinction between biomes and ecosystems. ecosystem classifications are specific kinds of ecological classifications that consider all four elements of the definition of ecosystems: a biotic component, an abiotic complex, the interactions between and within them, and the physical space they occupy. ecosystems provide a variety of goods and services upon which people depend. ecosystem goods include the "tangible, material products" of ecosystem processes such as water, food, fuel, construction material, and medicinal plants. ecosystem services, on the other hand, are generally "improvements in the condition or location of things of value". these include things like the maintenance of hydrological cycles, cleaning air and water, the maintenance of oxygen in the atmosphere, crop pollination and even things like beauty, inspiration and opportunities for research. many ecosystems become degraded through human impacts, such as soil loss, air and water pollution, habitat fragmentation, water diversion, fire suppression, and introduced species and invasive species. these threats can lead to abrupt transformation of the ecosystem or to gradual disruption of biotic processes and degradation of abiotic conditions of the ecosystem. once the original ecosystem has lost its defining features, it is considered "collapsed". ecosystem restoration can contribute to achieving the sustainable development goals. definition an ecosystem (or ecological system) consists of all the organisms and the abiotic pools (or physical environment) with which they interact.: 5 : 458 the biotic and abiotic components are linked together through nutrient cycles and energy flows. "ecosystem processes" are the transfers of energy and materials from one pool to another.: 458 ecosystem processes are known to "take place at a wide range of scales". therefore, the correct scale of study depends on the question asked.: 5 origin and development of the term the term "ecosystem" was first used in 1935 in a publication by british ecologist arthur tansley. the term was coined by arthur roy clapham, who came up with the word at tansley's request. tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.: 9 he later refined the term, describing it as "the whole system, ... including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment". tansley regarded ecosystems not simply as natural units, but as "mental isolates". tansley later defined the spatial extent of ecosystems using the term "ecotope". g. evelyn hutchinson, a limnologist who was a contemporary of tansley's, combined charles elton's ideas about trophic ecology with those of russian geochemist vladimir vernadsky. as a result, he suggested that mineral nutrient availability in a lake limited algal production. this would, in turn, limit the abundance of animals that feed on algae. raymond lindeman took these ideas further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. hutchinson's students, brothers howard t. odum and eugene p. odum, further developed a "systems approach" to the study of ecosystems. this allowed them to study the flow of energy and material through ecological systems.: 9 processes rainforest ecosystems are rich in biodiversity. this is the gambia river in senegal's niokolo-koba national park. flora of baja california desert, cataviña region, mexico external and internal factors ecosystems are controlled by both external and internal factors. external factors, also called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem. on broad geographic scales, climate is the factor that "most strongly determines ecosystem processes and structure".: 14 climate determines the biome in which the ecosystem is embedded. rainfall patterns and seasonal temperatures influence photosynthesis and thereby determine the amount of energy available to the ecosystem.: 145 parent material determines the nature of the soil in an ecosystem, and influences the supply of mineral nutrients. topography also controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. for example, ecosystems can be quite different if situated in a small depression on the landscape, versus one present on an adjacent steep hillside.: 39 : 66 other external factors that play an important role in ecosystem functioning include time and potential biota, the organisms that are present in a region and could potentially occupy a particular site. ecosystems in similar environments that are located in different parts of the world can end up doing things very differently simply because they have different pools of species present.: 321 the introduction of non-native species can cause substantial shifts in ecosystem function. unlike external factors, internal factors in ecosystems not only control ecosystem processes but are also controlled by them.: 16 while the resource inputs are generally controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading. other factors like disturbance, succession or the types of species present are also internal factors. primary production global oceanic and terrestrial phototroph abundance, from september 1997 to august 2000. as an estimate of autotroph biomass, it is only a rough indicator of primary production potential and not an actual estimate of it. primary production is the production of organic matter from inorganic carbon sources. this mainly occurs through photosynthesis. the energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels. it also drives the carbon cycle, which influences global climate via the greenhouse effect. through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen. the photosynthesis carried out by all the plants in an ecosystem is called the gross primary production (gpp).: 124 about half of the gross gpp is respired by plants in order to provide the energy that supports their growth and maintenance.: 157 the remainder, that portion of gpp that is not used up by respiration, is known as the net primary production (npp).: 157 total photosynthesis is limited by a range of environmental factors. these include the amount of light available, the amount of leaf area a plant has to capture light (shading by other plants is a major limitation of photosynthesis), the rate at which carbon dioxide can be supplied to the chloroplasts to support photosynthesis, the availability of water, and the availability of suitable temperatures for carrying out photosynthesis.: 155 energy flow energy and carbon enter ecosystems through photosynthesis, are incorporated into living tissue, transferred to other organisms that feed on the living and dead plant matter, and eventually released through respiration.: 157 the carbon and energy incorporated into plant tissues (net primary production) is either consumed by animals while the plant is alive, or it remains uneaten when the plant tissue dies and becomes detritus. in terrestrial ecosystems, the vast majority of the net primary production ends up being broken down by decomposers. the remainder is consumed by animals while still alive and enters the plant-based trophic system. after plants and animals die, the organic matter contained in them enters the detritus-based trophic system. ecosystem respiration is the sum of respiration by all living organisms (plants, animals, and decomposers) in the ecosystem. net ecosystem production is the difference between gross primary production (gpp) and ecosystem respiration. in the absence of disturbance, net ecosystem production is equivalent to the net carbon accumulation in the ecosystem. energy can also be released from an ecosystem through disturbances such as wildfire or transferred to other ecosystems (e.g., from a forest to a stream to a lake) by erosion. in aquatic systems, the proportion of plant biomass that gets consumed by herbivores is much higher than in terrestrial systems. in trophic systems, photosynthetic organisms are the primary producers. the organisms that consume their tissues are called primary consumers or secondary producers—herbivores. organisms which feed on microbes (bacteria and fungi) are termed microbivores. animals that feed on primary consumers—carnivores—are secondary consumers. each of these constitutes a trophic level. the sequence of consumption—from plant to herbivore, to carnivore—forms a food chain. real systems are much more complex than this—organisms will generally feed on more than one form of food, and may feed at more than one trophic level. carnivores may capture some prey that is part of a plant-based trophic system and others that are part of a detritus-based trophic system (a bird that feeds both on herbivorous grasshoppers and earthworms, which consume detritus). real systems, with all these complexities, form food webs rather than food chains. decomposition