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ecology

 
Dictionary: e·col·o·gy   (ĭ-kŏl'ə-jē) pronunciation
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n., pl., -gies.
    1. The science of the relationships between organisms and their environments. Also called bionomics.
    2. The relationship between organisms and their environment.
  2. The branch of sociology that is concerned with studying the relationships between human groups and their physical and social environments. Also called human ecology.
  3. The study of the detrimental effects of modern civilization on the environment, with a view toward prevention or reversal through conservation. Also called human ecology.

[German Ökologie : Greek oikos, house + German -logie, study (from Greek -logiā, -logy).]

ecological ec'o·log'i·cal (ĕk'ə-lŏj'ĭ-kəl, ē'kə-) or ec'o·log'ic (-ĭk) adj.
ecologically ec'o·log'i·cal·ly adv.
ecologist e·col'o·gist n.

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Britannica Concise Encyclopedia: ecology
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Study of the relationships between organisms and their environment. Physiological ecology focuses on the relationships between individual organisms and the physical and chemical features of their environment. Behavioral ecologists study the behaviours of individual organisms as they react to their environment. Population ecology is the study of processes that affect the distribution and abundance of animal and plant populations. Community ecology studies how communities of plant and animal populations function and are organized; it frequently concentrates on particular subsets of organisms such as plant communities or insect communities. Ecosystem ecology examines large-scale ecological issues, ones that often are framed in terms of measures such as biomass, energy flow, and nutrient cycling. Applied ecology applies ecological principles to the management of populations of crops and animals. Theoretical ecologists provide simulations of particular practical problems and develop models of general ecological relevance. See also systems ecology.

For more information on ecology, visit Britannica.com.

Sci-Tech Encyclopedia: Ecology
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The subdiscipline of biology that concentrates on the relationships between organisms and their environments; it is also called environmental biology. Ecology is concerned with patterns of distribution (where organisms occur) and with patterns of abundance (how many organisms occur) in space and time. It seeks to explain the factors that determine the range of environments that organisms occupy and that determine how abundant organisms are within those ranges. It also emphasizes functional interactions between co-occurring organisms. In addition to being a unique component of the biological sciences, ecology is both a synthetic and an integrative science since it often draws upon information and concepts in other sciences, ranging from physiology to meteorology, to explain the complex organization of nature.

Environment is all of those factors external to an organism that affect its survival, growth, development, and reproduction. It can be subdivided into physical, or abiotic, factors, and biological, or biotic, factors. The physical components of the environment include all nonbiological constituents, such as temperature, wind, inorganic chemicals, and radiation. The biological components of the environment include the organisms. A somewhat more general term is habitat, which refers in a general way to where an organism occurs and the environmental factors present there. See also Environment.

A recognition of the unitary coupling of an organism and its environment is fundamental to ecology; in fact, the definitions of organism and environment are not separate. Environment is organism-centered since the environmental properties of a habitat are determined by the requirements of the organisms that occupy that habitat. For example, the amount of inorganic nitrogen dissolved in lake water is of little immediate significance to zooplankton in the lake because they are incapable of utilizing inorganic nitrogen directly. However, because phytoplankton are capable of utilizing inorganic nitrogen directly, it is a component of their environment. Any effect of inorganic nitrogen upon the zooplankton, then, will occur indirectly through its effect on the abundance of the phytoplankton that the zooplankton feed upon. See also Phytoplankton; Zooplankton.

Just as the environment affects the organism, so the organism affects its environment. Growth of phytoplankton may be nitrogen-limited if the number of individuals has become so great that there is no more nitrogen available in the environment. Zooplankton, not limited by inorganic nitrogen themselves, can promote the growth of additional phytoplankton by consuming some individuals, digesting them, and returning part of the nitrogen to the environment.

Ecology is concerned with the processes involved in the interactions between organisms and their environments, with the mechanisms responsible for those processes, and with the origin, through evolution, of those mechanisms. It is distinguished from such closely related biological subdisciplines as physiology and morphology because it is not intrinsically concerned with the operation of a physiological process or the function of a structure, but with how a process or structure interacts with the environment to influence survival, growth, development, and reproduction.

Major subdivisions of ecology by organism include plant ecology, animal ecology, and microbial ecology. Subdivisions by habitat include terrestrial ecology, the study of organisms on land; limnology, the study of fresh-water organisms and habitats; and oceanography, the study of marine organisms and habitats.

The levels of organization studied range from the individual organism to the whole complex of organisms in a large area. Autecology is the study of individuals, population ecology is the study of groups of individuals of a single species or a limited number of species, synecology is the study of communities of several populations, and ecosystem, or simply systems, ecology is the study of communities of organisms and their environments in a specific time and place. See also Population ecology; Systems ecology.

Higher levels of organization include biomes and the biosphere. Biomes are collections of ecosystems with similar organisms and environments and, therefore, similar ecological properties. All of Earth's coniferous forests are elements in the coniferous forest biome. Although united by similar dynamic relationships and structural properties, the biome itself is more abstract than a specific ecosystem. The biosphere is the most inclusive category possible, including all regions of Earth inhabited by living things. It extends from the lower reaches of the atmosphere to the depths of the oceans. See also Biome; Biosphere.

The principal methodological approaches to ecology are descriptive, experimental, and theoretical. Descriptive ecology concentrates on the variety of populations, communities, and habitats throughout Earth. Experimental ecology involves manipulating organisms or their environments to discover the underlying mechanisms governing distribution and abundance. Theoretical ecology uses mathematical equations based on assumptions about the properties of organisms and environments to make predictions about patterns of distribution and abundance.

Dental Dictionary: ecology
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n

The study of the interaction between living organisms and their environment.

Geography Dictionary: ecology
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This term, coined by E. Haeckel in 1866, describes the study of the interrelationships between organisms and their surrounding, outer world; the study of animals and plants in relation to each other and to their habitats. Life forms, including man, are intimately linked with their environment. Production ecology, or community ecology, is the study of the structure of communities in terms of the throughput of energy and chemical compounds; key concepts are primary production, trophic levels, and nutrient cycles.

‘Ecology’, in everyday use, is linked with environmentalism, or the Green movement, perhaps because most ecological thinking is in favour of preservation of ecological processes, habitats, and species.

Political Dictionary: ecology
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From the Greek roots meaning ‘house study’. The German writer Ernst Haeckel defined ecology as ‘the science of relations between organisms and their environment’, a general definition which has remained acceptable. He first published the word Oekologie in his Generalle Morphologie in 1866.

The concept of ecology has always had three separate dimensions. (1) Overtly, it refers to an intellectual pursuit, the study of the system of interactions involving living things. (2) But it is also used to refer to the system itself: the reality of causal relationships between species. (3) Finally, ‘ecology’ has always been used by some people, though not generally by professional ecologists, to mean a substantive morality and a political programme inspired by the perception of the existence of an ecological system. Typically, the morality criticizes current human practice for its destruction of ecological systems and seeks to (re)create harmony between man and nature. Whether these objectives are possible (or even coherent) and what their relations are with the perceptions of scientific ecology form the central questions of political ecology.

The political (as opposed to the scientific) use of the term only became established after the period of intense environmental awareness in the Western world in the late 1960s and early 1970s. This period also diverted the attention of moral philosophers, in particular, the Norwegian philosopher Arne Naess, to the implications of the idea of ecology. Naess distinguished ‘Deep Ecology’ which was not ‘anthropocentric’ and which recognized principles of ‘biospherical egalitarianism’, ‘diversity and symbiosis’, and decentralization, from ‘Shallow Ecology’, the merely anthropocentric environmentalism which sought to conserve the earth's resources (whether beauty or fossil fuels) for man's use. The suggestion was that man must shift to the outlook of ‘Deep Ecology’ even to attain the more modest aims of shallow ecology. On Naess's own account the distinction and the key principles of ‘Deep Ecology’ were far from clear, but this essay, among others, struck an important chord in the concerns of the time and stimulated the growth of ‘green philosophy’, which has existed and developed at popular, polemical, and academic levels since.

There is a fundmental problem for ecological political theory, in that scientific studies of ecology do not offer a model of ecological stability nor an idea of a harmonious role for Homo sapiens within the ecological system. Rather, they develop the Darwinian model of an unstable, evolving system in which man, though not only man, crucially modifies the conditions of life for most other species, affecting their chances of survival, some for the worse, but perhaps even more for the better. Man cannot live in harmony with nature, if that means that his ecological role must be inert; nor can he fail to, in the sense that it is part of the role of all species within an ecological system to modify that system as an environment for other species.

Individual and collective choices cannot be ecologically right or ecologically wrong per se. However, there are powerful arguments for the looser suggestions that we should consider not only the detailed ecological consequences of our decisions, but also the nature of ecology, in considering the ‘environmental’ aspects of policy.

— Lincoln Allison

Encyclopedia of Judaism: Ecology
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The interaction between organisms and the environment. Judaism has always been concerned with the environment. An early reference to the need for conservation may be found in Deuteronomy 20:19-20, which states that when an army besieges a city it may not cut down fruit-bearing trees. Only non-fruit- bearing trees may be cut down to build bulwarks. Sifré specifically extends this rule to water resources, which may not be polluted---even in pursuit of war aims. R. Samson Raphael Hirsch, in his commentary on the Torah, understood the law regarding fruit-bearing trees as a paradigm, expressing a basic injunction against unwarranted destruction as such. Indeed, there is a specific law, generally known as Bal Tashḥit, which forbids the wanton destruction of any object.

When the 48 cities of the Levites were established, each was required to have a "green belt" of a thousand cubits around it, surrounded by another belt of 2,000 cubits of agricultural land (Num. 35:2-5). This belt of land could not be sold for any purpose. As Rashi points out, the green belt could not be used for building or farming. By analogy, Maimonides asserts that the same applies to any other city in Israel.

In addition, to protect the quality of life in the cities, abattoirs, cemeteries, threshing floors, and tanneries must be located outside city limits. Where odors might be offensive, such as in the case of a tannery, the installation must be located on the leeward side of the city. Thus the Talmud states that in Erets Israel, where the wind blows from the west, tanneries must be located to the east of the city.

To preserve the countryside, there was a rabbinic injunction against raising sheep or goats in Erets Israel, because their close grazing can leave the land denuded. Finally, the biblical requirement that an army bury its waste (Deut. 23:13-15) surely reflects ecological concern of the highest degree.

Philosophy Dictionary: ecology
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The science which investigates interacting systems of biological organisms.

Archaeology Dictionary: ecology
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[Ge]

The study of animals and plants in relation to their environment. Human ecology deals with human communities in relation to their environment. In archaeology, the ecological approach involves starting with the natural environment and examining the place of human communities within it. Such an approach has most utility for the Palaeolithic and Mesolithic periods.
Buddhism Dictionary: ecology
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This is a subject of modern concern about which classical Buddhist sources have little to say. Heightened by the interest in Engaged Buddhism, efforts are currently being made to develop a Buddhist ecology, with varying degrees of success. The main approaches draw upon traditional values such as compassion, (karuṇā), and less anthropocentric notions of the relationship between humans and nature than those found in the West. Due to the doctrine of rebirth, the relationship between man and animals is seen as closer, and Buddhists do not believe that the world was created for man's use and enjoyment, or that he stands in the position of divinely appointed steward over the rest of creation. Certain Mahāyāna interpretations of the doctrine of Dependent Origination (pratītya-samutpāda), particularly of the kind that arose in east Asia which see the universe as a cosmic network within which all phenomena are interrelated, also provide a foundation for ecological concern (see Indra's net). On the other hand, Buddhist ecology is hampered by the negative value Buddhism seems to place on the world in the First Noble Truth which teaches that life is suffering (duḥkha). Rather than a place to be cared for and preserved, the world is depicted in this strand of teaching as a place of woe and sorrow from which one should flee to the only form of durable happiness that exists, namely the transcendent state of nirvāṇa. Discussion of these issues is still at a rudimentary stage and it remains to be seen if a viable, critical Buddhist ecology can be established.

 
Columbia Encyclopedia: ecology
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ecology, study of the relationships of organisms to their physical environment and to one another. The study of an individual organism or a single species is termed autecology; the study of groups of organisms is called synecology.

The Ecosystem

Within the biosphere-the total expanse of water, land, and atmosphere able to sustain life-the basic ecological unit is the ecosystem. An ecosystem may be as small as a tidal pool or a rotting log or as large as an ocean or a continent-spanning forest. Each ecosystem consists of a community of plants and animals in an environment that supplies them with raw materials for life, i.e., chemical elements and water. The ecosystem is delimited by the climate, altitude, water and soil characteristics, and other physical conditions of the environment.

The Food Web and Other Vital Cycles

The energy necessary for all life processes reaches the earth in the form of sunlight. By photosynthesis green plants convert the light energy into chemical energy, and carbon dioxide and water are transformed into sugar and stored in the plant. Herbivorous animals acquire some of the stored energy by eating the plants; those animals in turn serve as food for, and so pass the energy to, predatory animals. Such sequences, called food chains, overlap at many points, forming so-called food webs. For example, insects are food for reptiles, which are food for hawks. But hawks also feed directly on insects and on other birds that feed on insects, while some reptiles prey on birds. Since a severe loss of the original energy occurs with each transfer from species to species, the ecologist views the food (energy) structure as a pyramid: Each level supports a smaller number and mass of organisms. Thus in a year's time it would take millions of plants weighing tons to feed the several steer weighing a few tons that could support one or two people. The ecological conclusion is that if human beings would eat more plants and fewer animals, food resources would stretch much further. Once the energy for life is spent, it cannot be replenished except by the further exposure of green plants to sunlight.

The chemical materials extracted from the environment and elaborated into living tissue by plants and animals are continually recycled within the ecosystem by such processes as photosynthesis, respiration, nitrogen fixation, and nitrification. These natural processes of withdrawing and returning materials are variously called the carbon cycle, the oxygen cycle, and the nitrogen cycle. Water is also cycled. Evaporation from lakes and oceans forms clouds; the clouds release rain that is taken up by the soil, absorbed by plants, and passed on to feeding animals-which also drink directly from pools and lakes that catch the rain. The water in plant and animal wastes and dead tissue then evaporates and can be recycled. Interference with these vital cycles by disturbance of the environment-for example, by pollution of the air and water-may disrupt the workings of the entire ecosystem. The cycles are facilitated when an ecosystem has a sufficient biological diversity of species to fill its so-called ecological niches, the different functional sites in the environment where organisms can act as producers of energy, consumers of energy, or decomposers of wastes. Such diversity tends to make a community stable and self-perpetuating.

Climax Communities

A climax community is one that has reached the stable stage. When extensive and well defined, the climax community is called a biome. Examples are tundra, grassland, desert, and the deciduous, coniferous, and tropical rain forests. Stability is attained through a process known as succession, whereby relatively simple communities are replaced by those more complex. Thus, on a lakefront, grass may invade a build-up of sand. Humus formed by the grass then gives root to oaks and pines and lesser vegetation, which displaces the grass and forms a further altered humus. That soil eventually nourishes maple and beech trees, which gradually crowd out the pines and oaks and form a climax community. In addition to trees, each successive community harbors many other life forms, with the greatest diversity populating the climax community.

Similar ecological zonings occur among marine flora and fauna, dependent on such environmental factors as bottom composition, availability of light, and degree of salinity. In other respects, the capture by aquatic plants of solar energy and inorganic materials, as well as their transfer through food chains and cycling by means of microorganisms, parallels those processes on land.

The early 20th-century belief that the climax community could endure indefinitely is now rejected because climatic stability cannot be assumed over long periods of time. In addition nonclimatic factors, such as soil limitation, can influence the rate of development. It is clear that stable climax communities in most areas can coexist with human pressures on the ecosystem, such as deforestation, grazing, and urbanization. Polyclimax theories stress that plant development does not follow predictable outlines and that the evolution of ecosystems is subject to many variables.

Bibliography

See E. P. Odum, Fundamentals of Ecology (3d ed. 1971); R. L. Smith, ed., The Ecology of Man: An Ecosystem Approach (1971); P. A. Colinvaux, Introduction to Ecology (1973); R. M. Darnell, Ecology and Man (1973); T. C. Emmel, An Introduction to Ecology and Population Biology (1973); D. B. Sutton and N. P. Harman, Ecology: Selected Concepts (1973); K. E. F. Watt, Principles of Environmental Science (1973); D. Worster, Nature's Economy (1977); R. Brewer, The Science of Ecology (1988).

Science Dictionary: ecology
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The study of living things, their environment, and the relation between the two.

Veterinary Dictionary: ecologist
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A person skilled in ecology.

Essay: Ecology and sociobiology
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Ecology is the science of the relationship between organisms and their environment. Some aspects were studied as early as 1789 or perhaps even earlier. The word itself was coined in 1866 (it means "study of the house"). But ecology really came into its own after World War II.

One reason for this is certainly the environmental movement that began seriously in 1962 with Rachel Carson's book Silent Spring and intensified in the 1970s. The popularity of environmental causes attracted people to ecology, sometimes in the mistaken belief that ecology is the science of avoiding pollution. Biologists might date their own environmental movement from publication in 1967 of The Theory of Island Biogeography by Robert MacArthur and Edward O. Wilson, which explored stability and fragility of species in restricted habitats.

Another reason for gains in ecology in the 1960s and 1970s has been the postwar development of the computer. Ecology is very much concerned with numbers and mathematical models, since it treats a great many individuals interacting with each other and with their physical surroundings all at once. Prewar models of how populations behave were computed by hand or with mechanical calculators. By the mid-1970s, an ecologist could feed a formula into a computer and see how a population stabilized, became periodic, or exploded depending on the choice of a single parameter. With such a tool in hand, much of the work in ecology during the 1960s and 1970s concentrated on finding how competition among species or individuals for niches -- ways of living -- affect populations. Energy distribution in populations also became easier to determine.

The realization in 1964 that apparently altruistic traits in species could be explained by the mathematics of Mendelian heredity led to sociobiology as a controversial offshoot of ecology. Calculations showed that among the social bees and ants a worker passes along more of her genetic heritage when the queen has all the children than when each worker has some of them (bee and ant workers are always female). Generalizing from this special example, Edward O. Wilson, a specialist in ants as well as biogeography, and others argued that many different types of social behavior in animals can be explained as mechanisms designed to transmit genes. Wilson's 1975 book Sociobiology: The New Synthesis aroused great controversy. People who believe that altruism in humans originates from nonbiological considerations fought against the precepts of sociobiology.

For a time, sociobiology was widely discussed, but popular interest in it faded. However, sociobiological ideas continue to influence much of the research on animal behavior (and some on human behavior). One scientific journal, for example, deals with Behavioral Ecology and Sociobiology. And while controversy over sociobiology is no longer in the popular press, thoughtful articles supporting or attacking the concepts continue to be a part of scientific discourse.

Gardener's Dictionary: ecology
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  1. The scientific study of the relationships between plants, animals, and their environment.
  2. The study of the detrimental effects of modern civilization on the environment, with a view toward prevention or reversal through conservation.


Word Tutor: ecology
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pronunciation

IN BRIEF: The science that deals with the relations between all living things and the conditions that surround them.

pronunciation An ecology professor visited our school today to demonstrate what we can do to protect the natural environment.

Quotes About: Ecology
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Quotes:

"We cannot cheat on DNA. We cannot get round photosynthesis. We cannot say I am not going to give a damn about phytoplankton. All these tiny mechanisms provide the preconditions of our planetary life. To say we do not care is to say in the most literal sense that we choose death." - Dame Barbara Ward

"How to be green? Many people have asked us this important question. It's really very simple and requires no expert knowledge or complex skills. Here's the answer. Consume less. Share more. Enjoy life." - Derek Wall

"The universe is like a safe to which there is a combination. Bit the combination is locked up in the safe." - Peter De Vries

"And he gave it for his opinion, that whoever could make two ears of corn, or two blades of grass, to grow upon a spot of ground where only one grew before, would deserve better of mankind, and do more essential service to his country, than the whole race of politicians put together." - Jonathan Swift

"Guns have metamorphosed into cameras in this earnest comedy, the ecology safari, because nature has ceased to be what it always had been -- what people needed protection from. Now nature tamed, endangered, mortal -- needs to be protected from people." - Susan Sontag

"The nation that destroys its soil destroys itself." - Franklin D. Roosevelt

See more famous quotes about Ecology

Wikipedia: Ecology
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For other uses, see Ecology (disambiguation).

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Blue Linckia Starfish.JPG Male lion on savanna.jpg

Hawk eating prey.jpg European honey bee extracts nectar.jpg

The science of ecology includes everything from global processes (above), the study of various marine and terrestrial habitats (middle) to individual interspecific interactions like predation and pollination (below).

Ecology (from Greek: οἶκος, "house" ; -λογία, "study of") is the interdisciplinary scientific study of the interactions between organisms and their environment.[1] Ecology is also the study of ecosystems. Ecosystems describe the web or network of relations among organisms at different scales of organization. Since ecology refers to any form of biodiversity, ecologists can conduct research on the smallest bacteria to the the global flux of atmospheric gases that are regulated by photosynthesis and respiration as organisms breath in and out of the biosphere. Ecology is a recent discipline that emerged from the natural sciences in the late 19th century. Ecology is not synonymous with environment, environmentalism, or environmental science.[1][2][3]

Like many of the natural sciences, a conceptual understanding of ecology is found in the broader details of study, including:

Ecology is distinguished from natural history, which deals primarily with the descriptive study of organisms. It is a sub-discpline of biology, which is the study of life.

There are many practical applications of ecology in conservation biology, wetland management, natural resource management (agriculture, forestry , fisheries), city planning (urban ecology), community health, economics, basic & applied science and it provides a conceptual framework for understanding and researching human social interaction (human ecology).[4][5][6][7]

Contents

Levels of organization and study

See also: Biological organisation

Ecology is challenged by a constant analytical problem of how to deal with different scales of pattern in space and time. Ecological processes can take decades and even hundreds of years to mature and cover broad geographic areas. Ecologists study ecosystems by sampling a certain number of individuals that are representative of a population. Long-term ecological studies, such as sites managed by the Long Term Ecological Network [1] including the Hubbard Brook study in operation since 1960 [2], provide important ecological track records. Most studies, however, cover only a fraction of the life-span in the development of an ecosystem, such as the different seral stages leading up to an old-growth forest. Ecology is also complicated by the fact that small scale patterns do not necessarily explain large scale phenomena, otherwise captured in the expression 'the sum is greater than the parts'.[8] These emergent phenomena operate at different environmental scales of influence, ranging from molecular to galactic spheres, and require different sets of scientific explanation.[9][10]

To simplify and place the study of ecology into a manageable framework of understanding, the biological world is conceptually organized as a nested hierarchy of individuality, ranging in scale from genes, to cells, to tissues, to organs, to organisms, to species and up to the level of the biosphere.[11] Ecosystems are primarily researched at (but not restricted to) three key levels of organization, including (1) organisms, (2) populations, and (3) communities. Ecosystems consist of communities containing different species of organisms. Communities consist of organisms living in different populations. [12][13] Ecosystem diversity is a part of biodiversity. Biodiversity includes all the varieties and processes of life, including organisms and their genetic differences that are evolutionarily classified into hierarchical, branching and coalescing dimensions.[14][15][16]

Ecological niche

Main article: Ecological niche
See also: Niche construction
We are not here concerned with an imaginary ecology based upon a hypothetical environment inhabited by fancied organisms evolved in some vaguely conceived system of life [...] Instead of dealing with imaginary situations, we are confronted by the ecology of the Earth as we know it, populated by organisms that have evolved here from the basis furnished principally by water, carbon dioxide, and their elements, together with nitrogen.
—Allee et al.[2]:73

The ecological niche is a central concept in ecology. There are many definitions of the niche dating back to 1917[17], but George Evelyn Hutchinson made conceptual advances on the concept in 1957[18][19] and introduced the most widely accepted definition:

"The niche is the set of biotic and abiotic conditions in which a species is able to persist and maintain stable population sizes."[17]:519

There are two differentiated kinds of ecological niche known as the fundamental and the realized niche. The fundamental niche describes the abiotic conditions under which a species is able to persist. The realized niche is the set of conditions under which a species persists in the context of other resource competitors or predators.[19][17][12] Organisms fit into a particular ecological niche according to their functional traits. A trait is a measurable property of an individual that strongly influences its performance.[20] Moreover, species become specialized within their niche and competitively exclude other species from living in the same geographic area if they fit into the same ecological niche. This is called the competitive exclusion principle.[21] Equally important to the concept of niche is habitat. The habitat describes the environment over which a species is known to occur and the type of community that is formed as a result.[22] For example, habitat might refer to an aquatic versus terrestrial environment that can be further categorized as montane or alpine.

Some of the biodiversity of a coral reef

Organisms are subject to environmental pressures, but they are also modifiers of their habitats. The regulatory feedback relationship between organisms and their environment can significantly modify conditions from a local scale (e.g., a pond) to global scale (e.g., Gaia) and they can also modify conditions over time even after an organism has passed away, such as the remnants of an old beaver dam or silica skeleton deposits from marine organisms.[23] This process of ecosystem engineering has also been called niche construction. Ecosystem engineers are defined as:

"...organisms that directly or indirectly modulate the availability of resources to other species, by causing physical state changes in biotic or abiotic materials. In so doing they modify, maintain and create habitats." [24]:373

Although it has long been understood that organisms modify their environment, the ecological engineering concept has stimulated a new appreciation for the degree of modification and the influence organisms have on the ecosystem and evolutionary process.[25][26] The niche construction concept highlights a previously under appreciated feedback mechanism of natural selection imparting forces on the abiotic niche.

"For example, many ant and termite species regulate temperature by plugging nest entrances at night or in the cold, by adjusting the height or shape of their mounds to optimize the intake of the sun’s rays, or by carrying their brood around their nest to the place with the optimal temperature and humidity for the brood’s development."[26]:10242

Population ecology

Main article: Population ecology

The first journal publication of the Society of Population Ecology, titled Population Ecology (originally called Researches on Population Ecology), was released in 1952.[3] Population ecology is concerned with the study of groups of organisms that live together in time and space. One of the first laws of population ecology is the Thomas Malthus' exponential law of population growth.[27] This law states that:

"...a population will grow (or decline) exponentially as long as the environment experienced by all individuals in the population remains constant."[27]:18

This simplified premise in population ecology provides the basis for formulating predictive theories and tests that follow. Simplified models in population ecology usually start with four key variables including death, birth, immigration, and emigration. The ecology of populations are simplified in the mathematical models that calculate changes in population demographics and evolution under the assumption (or null hypothesis) of no external influence. Some models can become more mathematically complex where "...several competing hypotheses are simultaneously confronted with the data."[28] For example, in a closed system where immigration and emigration does not take place, the per capita rates of change in a population can be mathematically described as:

dN / dT = B − D = bN − dN = (b − d)N = rN,

where N is the total number of individuals in the population, B is the number of births, D is the number of deaths, b and d are the per capita rates of birth and death respectively, and r is the per capita rate of population change. In simple terms, this formula can be understood as the rate of change in the population (dN/dT) is equal to births minus deaths (B - D).[27][29]

Using these techniques, Malthus' population principal of growth was later transformed into a mathematical model known as the logistic equation:

dN / dT = aN(1 − N / K),

where N is the biomass density, a is the maximum per-capita rate of change, and K is the carrying capacity of the population. The formula can be read as follows, the rate of change in the population (dN/dT) is equal to growth (aN) that is limited by carrying capacity (1-N/K). From these basic mathematical principals the discipline of population ecology expands into a field of investigation that queries the demographics of real populations and tests these results against those of various statistical models. Beyond these, the field of population ecology often uses data on life history and matrix algebra to develop projection matrices on fecundity and survivorship. This kind of information can be used for managing wildlife stocks and harvest quotas [30][29]

These mathematical models introduce two important variables that are commonly invoked in population ecology, namely r (intrinsic rate of natural increase in population size, density independent) and K (carrying capacity of a population, density dependent).[12] These two variables where used in development of the concept of r and K selection. An r-selected species (e.g., many kinds of insects, such as aphids[31]) is one that has high rates of fecundity, low levels of parental investment in the young, and high rates of mortality before individuals reach maturity. In r-selected species evolution favors productivity. In contrast, a K-selected species (such as humans) has low rates of fecundity, high levels of parental investment in the young, and low rates of mortality as individuals develop toward maturity. Evolution in K-selected species favors efficiency in the conversion of resources into fewer offspring.[32][33]

Community ecology

Main article: Community ecology
Community ecology examines how interactions among species and their environment affect the abundance, distribution and diversity of species within communities. Most theoretical and empirical studies within community ecology ignore genetic variation and evolutionary change within species, and instead assume that species comprise homogeneous non-evolving populations.
—Johnson & Stinchcomb[34]:250

Ecosystems are most generally studied at the local or effective community scale, such as measuring primary production in a wetland in relation to decomposition and consumption rates[35] or the analysis of predator-prey dynamics affecting amphibian biomass[36]. The vast majority of research into community ecology examines population dynamics of pairs of species to understand how entire communities function. Two conceptual models that have been used in understanding community ecology include food webs and trophic levels.[37][38]

Food webs

Main article: Food webs
Salamander Food Web
A schematic illustration of a salamander food-web in a pond.

Early naturalists in the 16th-18th century realized the importance of food and feeding as an agent of transfer for energy and nutrients among species. They determined that the supply ultimately depended upon plants converting energy from the sun into organic matter. Food webs are a type of concept map that is used for understanding real pathways in the series of ecological events usually starting with solar energy being photosynthesized in plants. Plants grow and accumulate nutrients that are in turn eaten by grazing herbivores and step by step the lines are drawn and until the web of life is illustrated.[39][40]

The first person to fully elaborate and place the concept of food chains into a scientific framework was Charles Elton in his classical book 'Animal Ecology'.[41] Elton[41] defined ecological relations using concepts of food-chains, food-cycles, food-size, and described numerical relations among different functional groups and their relative abundance. Elton's term 'food-cycle' was replaced by 'food-web' in a subsequent ecological text[42]. Elton's book broke conceptual ground by illustrating complex ecological relations through simpler food-web diagrams.[39] Food-webs are an effective way to conceptually illustrate and teach about the interactive links among species in a community.[43][44]

There are different dimensions in ecological communities that can be used to create more complicated food-webs, including: species composition (type of species), richness (number of species), biomass (the dry weight of plants and animals), productivity (rates of conversion of energy and nutrients into growth), and stability (food-webs over time). A food-web diagram illustrating species composition shows how a change in one single species can directly and indirectly influence many others. Microcosm studies are used to simplify food-web research into semi-isolated units such as small springs, decaying logs and cowpats. Principals gleaned from these food-web microcosm studies are used to extrapolate smaller dynamic concepts to larger systems.[45] Food-chain length is an important parameter in describing larger food-web dynamics and is defined as:

"The number of transfers of energy or nutrients from the base to the top of a food web..."[46]:269

There are different ways of calculating food-chain length depending on what parameters of the food-web dynamic are being considered: connectance, energy, or interaction.[46] Hence, in a simple predator-prey example a deer is one step removed from the plants it eats (chain length = 1) and a wolf that eats the deer is two steps removed (chain length = 2). The relative amount or strength of influence that these parameters have on the food-web are used to address questions about:

  • the identity or existence of a few dominant species (called strong interactors or keystone species)
  • the total number of species and food-chain length (including many weak interactors) and
  • how community structure, function and stability is determined.[45]

Trophic dynamics

Main article: Trophic dynamics
List of ecological functional groups, definitions and examples
Functional Group Definition and Examples
Producers or Autotrophs Usually plants or cyanobacteria that are capable of photosynthesis but could be other organisms such as the bacteria near ocean vents that are capable of chemosynthesis.
Consumers or Heterotrophs Animals, which can be primary consumers (herbivorous), or secondary or tertiary consumers (carnivorous and omnivores).
Decomposers or Detritivores Bacteria, fungi, and insects which degrade organic matter of all types and restore nutrients to the environment. The producers will then consume the nutrients, completing the cycle.

Links in food-webs relate of primary importance to feeding relations or trophism (The Greek root of the word troph, τροφή, trophē, means food or feeding). Elton[41] noted how important an influence the feeding relations had on ecosystem structure. He proposed that ecosystems naturally sort into a ‘pyramid of numbers’ when the relative abundance of each functional group is stacked into their respective trophic levels.

Functional groups are broadly categorized as autotrophs (e.g., plants), heterotrophs (e.g., deer, wolves), and detrivores (e.g., bacteria, fungi). It is not always entirely clear what creatures belong in what group. Some organisms are omnivores, meaning they eat both plant and animal tissues and don't fit neatly into a category. However, it has been suggested that omnivores have a greater functional ecosystem influence as predators because relative to herbivores they are comparatively inefficient at grazing.[47]

Trophic levels are part of the holistic or systems view of ecosystems. Each trophic level contains different species that share common ecological functions. Different species, such as ferns and lillys, are grouped very differently from an evolutionary view of their ecology, but functionally they both photosynthesize the sun's energy and classified as autotrophs. Grouping these functionaly similar species into a trophic system gives a macroscopic image of the larger functional design. Trophic levels are abstractions of the system, but they explain real phenomena. For example, the autotrophs have the highest global proportion of biomass, followed closely behind by microbes (prokaryotes - decomposers), then heterotrophs.[48][49] Functional trophic groups sort out hierarchically into pyramidic trophic levels because it requires specialized adaptations to become a photosynthesizer or a predator, but rarely are their organisms having a skillful combination of both functional abilities. Hence, functional adaptations to trophism (feeding) organizes different species into emergent functional groups.[47]

Two reconstructions of fossilized food-web ecosystems also illustrating trophic levels sorted vertically. Primary producers are at the base as red spheres, predator's are at the top as yellow spheres, and the lines represent feeding links. Original food-webs (on the left) are simplified on the right panels by aggregating groups that feed on the same foods into trophic species. S: number of species (nodes). L: number of trophic links. C: connectance; L/S2. MaxTL: maximum trophic level of a species in the web.[50]
A trophic pyramid

Functional groups are usually depicted in hierarchical schemes with three or more trophic levels including primary producers (autotrophs) and levels of heterotrophic consumers including the herbivores (primary consumers), predators (secondary consumers), predators that eat predators (tertiary consumers), and ultimately ending at the detrivores in the soil ecosystems.[51] The pyramidal arrangement of trophic levels is a consistent feature across ecosystems with the primary producers having the larger base and consumer densities and amounts of energy decreasing as species become further removed from the photosynthetic source of production.[52] The size of each level in the pyramid generally represents biomass, which is often measured as the dry weight of an organism.[51] Trophic levels and food webs can be used to depict and calculate mathematical and statistical parameters such as those used in other kinds of network analysis, including graph theory.[53]

Food-web links point to direct trophic relationships among species, but there are also indirect effects that can alter the abundance, distribution, or biomass in the trophic levels. For example, predators eating herbivores indirectly influence the control and regulation of primary production in plants. Although the predators do not eat the plants directly, they regulate the population of herbibores that are directly linked to plant trophism. The net effect of direct and indirect relations is called trophic cascades. Trophic cascades are separated into species-level cascades, where only a subset of the food-web dynamic is impacted by a change in population numbers, and community-level cascades, where a change in population numbers has a dramatic effect on the entire food-web, such as the distribution of plant biomass.[54]

The keystone species concept is closely aligned to species-level cascades, where a single species occupies a particularly strong node in the food-web and its removal results in the collapse of the food-web structure and extinction of other species. Sea otters (Enhydra lutris) are the classical example of a keystone species because they limit the density of urchins that feed on kelp. If sea otters are removed from the system, the urchins graze until the kelp beds disappear and this has a dramatic effect on community structure.[55] Hunting of sea otters, for example, is thought to have indirectly lead to the extinction of the Steller's Sea Cow (Hydrodamalis gigas).[56] While the keystone species concept has been used extensively as a conservation tool, it has been criticized for being poorly defined. Different ecosystems express different complexities and so it is unclear how applicable and general the keystone species model can be applied. To better understand the keystone species and trophic cascade models, ecologists conduct removal experiments to measure the relative impact, strength and influence of interaction among different species on community dynamics.[54][55]

Biosphere

The largest scale of ecological organization is the total sum of every ecosystem on the planet and the atmosphere it regulates, which is called the biosphere. Ecological relations regulate the flux of energy, nutrients, and climate all the way up to the planetary scale. For example, the dynamic history of the planetary CO2 and O2 composition of the atmosphere has been largely regulated by the biogenic flux of gases coming from respiration and photosynthesis with levels fluctuating in time and in relation to the ecology and evolution of plants and animals.[57] When sub-component parts, such as the full variety of ecosystems diversifying the planet, are organized into a whole there are oftentimes identifiable properties or characteristics that describe the nature of the system under investigation. Ecological theory has been used to explain self emergent regulatory phenomena at the planetary scale. This is known as the Gaia hypothesis[10]. The Gaia hypothesis is an example of holism in ecology because it tests for principals relating to an evolving and self regulating planetary ecosystem that requires different explanations than those governing ecosystems at a smaller scale.[58]

Ecology and evolution

Ecology and evolution are considered sister disciplines. Ecology and evolution are academic branches of the life sciences. Natural selection, life history, development, adaptation, populations, and inheritance all play an prominent conceptual roles in ecological as well as evolutionary theory. Both disciplines also employ genetics in their investigations. For example, morphological, behavioural and/or genetic traits can be mapped onto evolutionary trees to study principals of inheritance that relates back to the ecology of adaptations. Ecology and evolution are scientifically connected because they both study hierarchies, networks, relations, and kinship among genes, cells, individuals, communities, species, and the biosphere.[59] The two disciplines often appear together, such as in the title of the journal Trends in Ecology and Evolution.[60] There is no sharp dichotomous boundary that separates ecology from evolution and differ more in their areas of applied focus. Both disciplines discover and explain emergent and unique properties and processes operating across different spatial or temporal scales of organization.[61][10][62] While the boundary between ecology and evolution is not always clear, it is understood that ecology studies the abiotic and biotic factors that influence the evolutionary process.[2][51]

Behavioral ecology

Main article: Behavioral ecology

Behavioural ecology is the field of study concerned with ethology and its implications to broader ecological theory. Adaptation is the central unifying concept in behavioral ecology.[4] Behaviors can be recorded as traits and inherited in much the same way that eye and hair color can. As such, behaviors are subject to the forces of natural selection.[63] Hence, behaviors can be adaptive in nature, meaning that they evolved and serve a functional utility such as enhancing ones opportunity to successfully reproduce and increase fitness.[64] Fitness is measured in terms of reproductive success. An animal with behaviors that afford it some degree of leverage in the struggle for existence such that it survives to pass on its heritable traits to its offspring is considered fit if the adaptation succeeds and propagates more of its kind in subsequent generations. A measure of fitness is the numerical differential and representation in frequency of a trait over subsequent generations.[63]

Predator-prey interactions are a fundamental and introductory concept in food-web studies as well as behavioural ecology.[65] Prey species can exhibit different kinds of behavioural adaptations to predators, such as avoid, flee or defend. Many prey species are faced with multiple predators that differ in the degree of danger posed. To be adapted to their environment and predatory threats, organisms must balance their energy budgets as they invest in different aspects of their life history, such as feeding, mating, socializing, or modifying their habitat. Hypotheses posited in behavioural ecology are generally based on adaptive principals of conservation or efficiency. For example,

"The threat-sensitive predator avoidance hypothesis predicts that prey should assess the degree of threat posed by different predators and match their behavior according to current levels of risk."[66]

"The optimal flight initiation distance occurs where expected postencounter fitness is maximized, which depends on the prey’s initial fitness, benefits obtainable by not fleeing, energetic escape costs, and expected fitness loss due to predation risk."[67]

The behaviour of long-toed salamanders (Ambystoma macrodactylum) present another example in this context. When threatened, the long-toed salamander will defend itself by waving its tail and secreting a white milky fluid.[68][69] The excreted fluid is distasteful, toxic and adhesive, but it is also used for nutrient and energy storage during hibernation. Hence, salamanders subjected to frequent predatory attack will be energetically compromised as they use up their energy stores.[70] [71] Some species are also able to avoid predators altogether, such as small velvet gecko's (Oedura lesueurii). This species is specially adapted to smell the body chemicals of snakes that linger after they pass through an area, even though snakes rarely pose a significant danger.[66]

A often quoted hypothesis in behavioural ecology is known as Lack's brood reduction hypothesis, which posits an evolutionary and ecological explanation as to why birds often lay a series of eggs with an asynchronous delay such that the young are of mixed age and weights. According to Lack, this brood-reducation behaviour is a sort of ecological insurance that allows some birds to survive in poor years and all birds to survive when food is plentiful.[72][73]

"The clutch size of each species of bird is characteristic, and in general seems adapted to correspond with the largest number of young which can be successfully raised. Probably there is a small hereditary variation, which is explicable through rather larger clutches being favoured in some years and rather smaller clutches in other years."[74]:333

Elaborate sexual displays and posturing are often encountered in the behavioural ecology of animals. Many birds, for example, display elaborate ornaments during courtship. These displays serve a dual purpose of signalling healthy or well-adapted individuals and good genes. The elaborate displays are driven by sexual selection as the displays serve as an advertisment of quality traits in sexual partners.[75]

Biogeography

Main article: Biogeography

As the name implies, biogeography is an amalgamation of the words biology and geography. The word was first coined by the German geographer, Friedrich Ratzel in 1891.[76] The Journal of Biogeography was established in 1974 and publishes "...papers dealing with all aspects of spatial, ecological and historical biogeography."[5]Biogeography and ecology share much of the same disciplinary roots. For example, the theory of island biogeography, elucidated by Robert MacArthur and E. O. Wilson in 1967[32] is considered one of the fundamentals of ecological theory.[77]

Biogeography has a long and rich history in the natural sciences where questions arise concerning the spatial distribution of plants and animals. Ecology and evolution provides the explanatory context for biogeographical studies.[76] Biogeographical patterns result from ecological processes that influences dispersal (or dispersion)[77] and from historical processes that split populations or species into different areas.[78] The biogeographic processes that result in the natural splitting of species explains much of the modern distribution of the Earth's biota. This area of focus is called vicariance biogeography and it is a sub-discipline of biogeography. It is a separate discipline because it specifically studies the branching, phylogenetic, or speciation process in evolutionary studies and explains much of the patterns in biodiversity across the globe.[78][79][80]

There are many applications in the field of biogeography that concern ecological systems and processes. For example, the range and distribution of biodiversity and invasive species responding to climate change is a serious concern and active area of research in context of global warming. [81] [82]

Molecular Ecology

Main article: Molecular ecology

There has long been an understanding of the important relationship between ecology and genetic inheritance.[2] This branch of research became more feasible with the development of genetic technologies, such as the polymerase chain reaction (PCR), and through the publication Molecular Ecology starting in 1992.[83] Molecular ecology uses various analytical techniques to study genes in evolutionary and ecological context. In 1994, professor John Avise played a leading role in popularizing this field of study through the publication of his book, Molecular Markers, Natural History and Evolution .[84] Newer genetic technologies made genetic sampling of organisms simpler and engendered a new and collaborative research paradigm that investigates and probes ecological questions that were otherwise intractable. Molecular ecology revealed previously obscured details in the intricacies of nature and improved resolution into probing questions about behavioural and biogeographical ecology. For example, molecular ecology revealed promiscuous sexual behaviour that is driven by female choice in pocket gophers [85] and multiple male partners in tree swallows previously thought to be socially monogamous.[86] In a biogeographical context, the marriage between genetics, ecology and evolution created a new sub-discipline called phylogeography.[87]

Ecology and the environment

The environment is external yet interlinked directly with ecology. Chemistry, temperature, pressure, gravity, energy, and sunlight are properties of Earth's environment that are relevant to ecology. Environmental and ecological relations are often studied through conceptually and practically manageable parts. However, once the effective environmental components are understood they conceptually link as a holocoenotic[6] system.

Ecology is often misused as a synonym for environment, but it differs from environmental studies, for example, because it is one of the few academic disciplines dedicated to holism.[9] The environment describes all factors and scales of study that are external to an organism, including abiotic factors such as temperature, radiation, light, chemistry, climate and geology, and biotic factors, including genes, cells, organisms, members of the same species (conspecifics) and other species that share a habitat.[88] In contrast, ecology focuses on biological relations and studies how these relate to the environment.[9] Ecosystem processes are consistent with the laws of thermodynamics. Armed with an understanding of metabolic and thermodynamic principles, a complete accounting of energy and material flow can be traced through an ecosystem.[89]

Metabolism and the early atmosphere

Metabolism – the rate at which energy and material resources are taken up from the environment, transformed within an organism, and allocated to maintenance, growth and reproduction – is a fundamental physiological trait.
—Ernst et al.[90]:991

The Earth's environment has not always remained at a constant temperature and the atmosphere has changed significantly as a result of the gross metabolic activity of life on Earth. There is an evolving feedback loop between the ecological processes of life, geochemistry, and Earth's atmosphere. Proceeding through the early stages of life, major ecological transitions modified the Earth's geochemical cycles. The Earth formed approximately 4.5 billion years ago[91] and environmental conditions were too extreme for life to form for the first 500 million years. During this early Hadean period, the Earth started to cool allowing time for a crust and oceans to form. Environmental conditions were unsuitable for the origins of life until approximately 1 billion years after the Earth formed. The Earth's atmosphere transformed from hydrogen dominant, to one composed mostly of methane, and ammonia. Over the next billion years the metabolic activity of life transformed the atmosphere to higher concentrations of carbon dioxide, nitrogen, and water vapor. These gases changed the way that light from the sun hit the Earth's surface and greenhouse effects trapped in heat. There were untapped sources of free energy within the mixture of reducing and oxidizing gasses that set the stages for primitive ecosystems to evolve and, in turn, the atmosphere also evolved.[92]

The leaf is the primary site of photosynthesis in plants.

One of the earliest organisms was likely an anaerobic methanogen microbe that would have converted atmospheric hydrogen into methane (4H2 + CO2 → CH4 + 2H2O). Anoxygenic photosynthesis converting hydrogen sulfide into other sulfur compounds or water (2H2S + CO2 → hv → CH2O → H2O → + 2S or 2H2 + CO2 + hv → CH2O + H2O), as occurs in deep sea hydrothermal vents today, would have also reduced hydrogen and increased atmospheric methane. Early forms of fermentation would have also been a component of the primitive ecology producing higher levels of atmospheric methane. The transition to an oxygen dominant atmospheric transition did not begin until approximately 2.4-2.3 billion years ago, but photosynthetic processes had started 0.3 to 1 billion years prior. Hence, the transition to an oxygen environment was ecologically latent.[93] The evolution of the Earth's ecosystems demonstrates how smaller scale metabolic processes of life can regulate larger scale environmental phenomena, such as the Earth's atmosphere. This relationship has led to the development of the Gaia hypothesis, which states that there is a feedback process generated by living organisms that maintains the temperature of the Earth and atmospheric conditions within a narrow self-regulating range of tolerance. Hence, the gross ecology of the planet acts as a single regulatory or holistic unit called Gaia.[10]

Radiation: light, heat, and temperature

Almost all aspects of functional ecology is effected indirectly or directly by radiant energy from the sun. There are different wavelengths of electromagnetic energy emanating from the sun that provides inputs into the ecological energy budget of the planet. Radiant energy from the sun generates heat, provides photons of light measured as active energy in the chemical reactions of life, and also acts as a catalyst for genetic mutation.[2][51][89]

The biology of life operates within a certain range of temperatures. Heat is a form of energy that regulates temperature. Heat affects growth rates, activity, behaviour and primary production. Temperature is largely dependent on the incidence of solar radiation. The latitudinal and longitudinal spatial variation of temperature greatly affects climates and consequently the distribution of biodiversity and levels of primary production in different ecosystems or biomes across the planet. Heat and temperature also relate importantly and differently affects two metabolic divisions in animals, poikilotherms, having a body temperature that is largely regulated and dependent on the temperature of the external environment, and homeotherms, having a body temperature that is internally regulated and maintained by expending metabolic energy.[2][51][89]

Light is the primary source of energy on the planet. Plants, algae, and some bacteria absorb light and assimilate the energy through photosynthesis. Organisms capable of assimilating energy by photosynthesis or through inorganic fixation of H2S are autotrophs. Autotrophs are responsible for primary production and the assimilation of light energy that becomes metabolically stored as potentional energy in biochemical enthalpic bonds. Heterotrophs feed on autotrophs for their supply of energy and nutrients. Hence, there is a relationship between light, production, and supplies of energy that affects the distribution, composition and structure of ecosystem dynamics across the planet.[2][51][89]

Physical environments

Water

Main article: Aquatic ecosystem

The rate of diffusion of carbon dioxide and oxygen is approximately 10,000 times slower in water than it is in air. When soils become flooded, they quickly loose oxygen from low-concentration (hypoxic) to an (anoxic) environment where anaerobic bacteria thrive among the roots[94]. Aquatic plants exhibit a wide variety of morphological and physiological adaptations that allow them to survive, compete and diversify these environments. For example, the roots and stems develop large cellular air spaces to allow for the efficient transportation gases (for example, CO2 and O2) used in respiration and photosynthesis. In drained soil, microorganisms use oxygen during respiration. In aquatic environments, anaerobic soil microorganisms use nitrate, manganic ions, ferric ions, sulfate, carbon dioxide and some organic compounds. The activity of soil microorganisms and the chemistry of the water reduces the oxidation-reduction potentials of the water. Carbon dioxide, for example, is reduced to methane (CH4) by methanogen bacteria. Salt water also requires special physiological adaptations to deal with water loss. Salt water plants (or halophytes) are able to osmo-regulate their internal salt (NaCl) concentrations or develop special organs for shedding salt away.[94]. The physiology of fish is also specially adapted to deal with high levels of salt through osmoregulation. Their gills form electrochemical gradients that mediate salt excrusion in salt water and uptake in fresh water.[95]

Wetland conditions such as shallow water, high plant productivity, and anaerobic substrates provide a suitable environment for important physical, biological, and chemical processes. Because of these processes, wetlands play a vital role in global nutrient and element cylcles.:29[94]

Gravity

The shape and energy of the land is affected to a large degree by gravitational forces. On a larger scale, the distribution of gravitational forces on the earth are uneven and influence the shape and movement of tectonic plates as well as having an influence on geomorphic processes such as orogeny and erosion. These forces govern some of the geo-physical properties and distributions of biomes across the Earth. On a organism scale, gravitational forces provide directional cues for plant and fungal growth (gravitropism), orientation cues for animal migrations, and influences the biomechanics and size of animals.[2]

Pressure

Pressure effects the environment and the organism. It acts as a mechanical force with close connections to gravity causing increased levels of pressure moving toward the Earth. Pressure exerts significant influence over the atmosphere, climate, water environments, and on smaller scale there are osmotic forces at work. Organisms are physiologically sensitive and adapted to atmospheric and osmotic water pressures.[2] Water transportation through trees, for example, is an important eco-physiological parameter.[96][97] Water pressure in the depths of oceans requires adaptations to deal with the different living conditions. Mammals, such as whales, dolphins and seals require special adaptations to deal with the change in sound due to water pressure differences.[98] Climatic and osmotic pressure places physiological constraints on organisms, such as flight and respiration at high altitudes, or diving to deep ocean depths. These constraints influence vertical limits of ecosystems in the biosphere.[2]

Wind and turbulence

Turbulent forces in air and water have significant effects on the environment and ecosystem distribution, form and dynamics. On a planetary scale, ecosystems are affected by circulation patterns in the global trade winds. Locally, wind power and the turbulent forces it creates can influence heat, nutrient, and biochemical profiles of ecosystems.[2] For example, winds running over the surface of lakes winds creates turbulence that stirs the water column and influences the environmental profile to create thermally layered zones that partially governs how the fish, algae, and other parts of the aquatic ecology are structured.[99][100] Wind speed and turbulence also exert influence on rates of evapotranspiration rates and energy budgets in plants and animals [94][101]

Fire

Main article: Fire ecology

Plants spew oxygen into the atmosphere. Approximately 350 million years ago the photosynthetic process brought atmospheric oxygen levels above 17% in concentration, which allowed for the combustion of fire.[102] Fire releases CO2 and converts fuel into ash and tar. Fire is a significant ecological parameter that raises many issues pertaining to its control and suppression in management.[103] While the issue of fire in relation to ecology and plants has been recognized for a long time[104], Charles Cooper brought attention to the issue of forest fires in relation to the ecology of forest fire suppression and management in the 1960s.[105][106] The association for fire ecology launched a journal, "Fire Ecology", in 2005 that is specifically devoted to the study of fire ecology and management.[7].

Fire creates environmental mosaics and a patchiness to ecosystem age and canopy structure. Native North Americans were among the first to influence fire regimes by controlling their spread near their homes or by lighting fires to stimulate the production of herbaceous foods and basketry materials.[107] Most ecosystem are adapted to some level of natural fire cycles. Plants, for example, are equipped with a variety of special adaptations to deal with forest fires. The altered state of soil nutrient supply and cleared canopy structure creates a new niche for seedling establishment.[108][109] Some species (e.g., Pinus halepensis) cannot germinate until after their seeds have lived through a fire. This environmental trigger for seedlings is called serotiny.[110] Some compounds from smoke also promote seed germination.[111]

Biogeochemistry

Main article: Biogeochemistry

Ecologists study and measure nutrient budgets to understand how these materials are regulated and flow through the environment.[2][51][89] This research has led to an understanding that there is a global feedback between ecosystems and the physical parameters of this planet including minerals, soil, pH, ions, water and atmospheric gases. There are six major elements, including H (hydrogen), C (carbon), N (nitrogen), O (oxygen), S (sulfur), and P (phosphorus) that form the constitution of all biological macromolecules and feed into the Earth's geochemical processes. From the smallest scale of biology the combined effect of billions upon billions of ecological processes amplify and ultimately regulate the biogeochemical cycles of the Earth. Understanding the relations and cycles mediated between these elements and their ecological pathways has significant bearing toward understanding global biogeochemistry.[112]

The ecology of global carbon budgets gives one example of the linkage between biodiversity and biogeochemistry. For starters, the ocean is estimated to hold 40,000 Gt carbon, vegetation and soil is estimated to hold 2070 Gt carbon, and fossil fuel emissions are estimated to emit an annual flux of 6.3 Gt carbon.[113] At different times in the Earth's history there has been major restructuring in these global carbon budgets that was regulated to a large extent by the ecology of the land. For example, through the early-mid Eocene volcanic out gassing, the oxidation of methane stored in wetlands, seafloor gases and/or combinations thereof increased CO2 concentrations to levels as high as 3500 ppm.[114] In the Oligocene, from 25 to 32 million years ago, there was another significant restructuring in the global carbon cycle as grasses evolved a special type of C4 photosynthesis and expanded their ranges. This new photosynthetic pathway evolved in response to the drop in atmospheric CO2 concentrations below 550 ppm.[115] Ecosystem functions such as these feed back significantly into global atmospheric models for carbon cycling. Loss in the abundance and distribution of biodiversity causes global carbon cycle feedbacks that are expected to increase rates global warming in the next century.[116] Global warming melting large sections of permafrost creates a new mosaic of flooded areas where decomposition emits methane (CH4). Hence, there is a relationship between global warming, decomposition and respiration in soils and wetlands producing significant climate feedbacks and alters global biogeochemical cycles.[117][118] There is concern over methane increases in the atmosphere in context of the carbon cycle, because methane is also a greenhouse gas that is 23 times more effective at absorbing long-wave radiation on a 100 year time scale.[119]

Historical roots of ecology

Main article: History of ecology

In the early 20th century, ecology was called scientific natural history and was influenced by the analytical precision of Newtonian sciences.[120] A comprehensive historical account of ecology is a complicated task because ecology is one of the most diverse of the scientific disciplines.[121] Several published books provide extenstive coverage of the classics.[122][123] The term "ecology" (German: Oekologie) is a more recent scientific development and was first coined by the German biologist Ernst Haeckel in his book Generelle Morpologie der Organismen (1866). The definition offered by Haeckel appeared in the frontispiece of the classical text Principles of Animal Ecology.[2]

By ecology we mean the body of knowledge concerning the economy of nature-the investigation of the total relations of the animal both to its inorganic and its organic environment; including, above all, its friendly and inimical relations with those animals and plants with which it comes directly or indirectly into contact-in a word, ecology is the study of all those complex interrelations referred to by Darwin as the conditions of the struggle of existence.
—Haeckel's definition quoted in Esbjorn-Hargens[124]:6

ErnstHaeckel.jpg Warming,Eug1879.jpg

Ernst Haeckel (left) and Eugenius Warming (right), two early founders of ecology.

While some mark Haeckel's definition as the beginning of ecology, others posit that the science of ecology began with Carl Linnaeus' research principals on the economy of nature that matured in the early 18th century.[125][39] The works of Carl Linnaeus influenced Darwin as evidenced by his reference to ecology through his adopted usage of Linnaeus' phrase economy or polity of nature in The Origin of Species.[126] Ernst Haeckel was strongly influenced by Darwin's work, defined ecology in reference to the economy of nature and this has lead some to question if ecology is synonymous with Linnaeus' concepts for the economy of nature.[125] Some have suggested that ecology started with Alexander von Humbolt (1809-1882), who was also admired by Charles Darwin.[120] Baron Humbolt was among the first to recognize ecological gradients and alluded to the modern law of species to area relationships in ecology.[127][128]

The modern synthesis of ecology is a young science that flourished and attracted much research attention around the same time as evolutionary studies at the end of the 19th century. However, many observations, interpretations and discoveries relating to ecology extend back to much earlier studies in natural history. For example, the concept on the balance or regulation of nature can be traced back to Herodotos (died c. 425 BC) who described an early account of mutualism along the Nile river where crocodiles open their mouths to beneficially allow sandpipers safe access to pluck leaches away.[121]. In the broader contributions to the historical development of the ecological sciences, Aristotle is considered one of the earliest naturalists who had a highly influential role in the philosophical development of ecological sciences. One of Aristotle's students, Theophrastus, made astute ecological observations about plants and posited a philosophical stance about the autonomous relations between plants and their environment that is more in line with modern ecological thought. Both Aristotle and Theophrastus made extensive observations on plant and animal migrations, biogeography, physiology, and their habits in what might be considered a modern analog of the ecological niche.[129][130]

Carl Linnaeus (1707–1778), a well known naturalist also holds a prominent place in the history of ecological sciences as he invented the first branch of ecological study he called the economy of nature.[39] Linnaeus was one of the first to attempt to define on the balance of nature, which had previously been held as an assumption rather than formulated as a testable hypothesis. From Aristotle to Darwin, however, the natural world was predominantly considered static and unchanged since its original creation. Hence, there was little appreciation and understanding for the dynamic and reciprocal relations between organisms, their adaptations and modifications to the environment.[131][124]


Nowhere can one see more clearly illustrated what may be called the sensibility of such an

organic complex,--expressed by the fact that whatever affects any species belonging to it, must speedily have its influence of some sort upon the whole assemblage. He will thus be made to see the impossibility of studying any form completely, out of relation to the other forms,--the necessity for taking a comprehensive survey of the whole as a condition to a satisfactory

understanding of any part.
—Stephen Forbes (1887)[132]

While Charles Darwin is most notable for his treatise on evolution[133], he was also a notable and astute ecologist as he meticuously researched earthworms in relation to soil ecology[134] and in The Origin of Species he made note of the very first ecological experiment that was published in 1816.[135][136] In the science leading up to Darwin the notion of evolving species was gaining popular support. This scientific paradigm changed the way that researchers approached the ecological sciences.

The first American ecology book was published in 1905 by Frederic Clements.[137] Frederic Clements forwarded the idea of plant communities as a superorganism. According to this premise, single species populations could be classified, using identifiable plant associations, into larger superorganism entities that were believed to progress through regular and determined stages of seral development analogous to developmental stages of a single organism. Not until the 1970's had the Clementsian paradigm been overthrown by the Gleasonian paradigm [138] which emphasized the overriding role of individual organisms and their life histories in the development of community associations.[139]

Notable pioneers and their contributions to ecology.
Notable figure Lifespan Major contribution & citation
Carl Linnaeus 1707–1778 Influential naturalist, inventor of science on the economy of nature[39][125]
Alexander Humboldt 1769–1859 First to describe ecological gradient of latitudinal biodiversity increase toward the tropics[8] in 1807[128]
Charles Darwin 1809-1882 Founder of evolution by means of natural selection, founder of ecological studies of soils[133][134]
Herbert Spencer 1820–1903 Early founder of social ecology, coined the phrase 'survival of the fittest'[125][140]
Karl Möbius 1825-1908 First to develop concept of ecological community, biocenosis, or living community[141][142][143]
Ernst Haeckel 1834-1919 Invented the term ecology, popularized research links between ecology and evolution[124][126]
Victor Hensen 1835-1924 Invented term plankton, developed quantitative and statistical measures of productivity in the seas[126]
Eugenius Warming 1841-1924 Early founder of Ecological Plant Geography[144]
Stephen Forbes 1844–1930 Early founder of entomology and ecological concepts in 1887[9][145][132]
Henry C. Cowles 1869-1939 Pioneering studies and conceptual developing in ecological succession[146]
Arthur G. Tansley 1871–1955 First to coin the term ecosystem in 1936 and notable researcher[147][142][148]
Charles Christopher Adams 1873-1955 Animal ecologist, biogeographer, author of first American book on animal ecology in 1913, founded ecological energetics[149][150]
Frederic Clements 1874-1945 Authored the first influential American ecology book in 1905[138]
Victor Ernest Shelford 1877-1968 Founded physiological ecology, pioneered food-web and biome concepts, founded The Nature Conservancy[151][152]
Henry Gleason 1882-1975 Early ecology pioneer, quantitative theorist, author, and founder of the individualistic concept of ecology[153][138]
Charles S. Elton 1900-1991 'Father' of animal ecology, pioneered food-web & niche concepts and authored influential Animal Ecology text[154][151]
G. Evelyn Hutchinson 1903-1991 Limnologist and conceptually advanced the niche concept[155][156][157]
Eugene P. Odum 1913-2002 Co-founder of ecosystem ecology and ecological thermodynamic concepts[148][151][158][159]
Howard T. Odum 1924–2002 Co-founder of ecosystem ecology and ecological thermodynamic concepts[148][151][160][161][158][159]

See also

Environment portal
Ecology portal
Biology portal
Earth sciences portal
Sustainable development portal
Main article: Outline of ecology
Bachalpsee in the Swiss Alps; generally mountainous areas are less affected by human activity.

Lists

Notes

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References

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Translations: Ecology
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Home > Library > Literature & Language > Translations

Dansk (Danish)
n. - økologi

Nederlands (Dutch)
ecologie

Français (French)
n. - écologie

Deutsch (German)
n. - Ökologie

Ελληνική (Greek)
n. - οικολογία

Italiano (Italian)
ecologia

Português (Portuguese)
n. - ecologia (f)

Русский (Russian)
экология

Español (Spanish)
n. - ecología

Svenska (Swedish)
n. - ekologi

中文（简体）(Chinese (Simplified))
生态学

中文（繁體）(Chinese (Traditional))
n. - 生態學

한국어 (Korean)
n. - 생태학

日本語 (Japanese)
n. - 生態学, エコロジー, 生態環境

العربيه (Arabic)
‏(الاسم) علم البيئه‏

עברית (Hebrew)
n. - ‮תורת הסביבה, אקולוגיה‬

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