Ecology

Ecosystems vary from tiny to vast. A single tree is of little consequence to the classification of a forest ecosystem, but is critically relevant to organisms living in and on it. The main subdisciplines of ecology, population (or community) ecology and ecosystem ecology, differ in their contrasting paradigms. The former focuses on organisms' distribution and abundance, while the latter focuses on materials and energy fluxes. Hierarchy To structure the study of ecology into a conceptually manageable framework, the biological world is organized into a hierarchy, ranging in scale from (as far as ecology is concerned) organisms, to populations, to guilds, to communities, to ecosystems, to biomes, and up to the level of the biosphere. Biodiversity includes species diversity, ecosystem diversity, and genetic diversity and scientists are interested in the way that this diversity affects the complex ecological processes operating at and among these respective levels. Conservation priorities and management techniques require different approaches and considerations to address the full ecological scope of biodiversity. Natural capital that supports populations is critical for maintaining ecosystem services or use models that can become mathematically complex as "several competing hypotheses are simultaneously confronted with the data." Food webs A food web is the archetypal ecological network. Plants capture solar energy and use it to synthesize simple sugars during photosynthesis. As plants grow, they accumulate nutrients and are eaten by grazing herbivores, and the energy is transferred through a chain of organisms by consumption. The simplified linear feeding pathways that move from a basal trophic species to a top consumer is called the food chain. Food chains in an ecological community create a complex food web. Food webs are a type of concept map used to illustrate and study pathways of energy and material flows. Species are broadly categorized as autotrophs (or primary producers), heterotrophs (or consumers), and Detritivores (or decomposers). Autotrophs are organisms that produce their own food (production is greater than respiration) by photosynthesis or chemosynthesis. Heterotrophs are organisms that must feed on others for nourishment and energy (respiration exceeds production). Sea otters (Enhydra lutris) are commonly cited as an example because they limit the density of sea 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. == Complexity ==

Complexity is understood as a large computational effort needed to assemble numerous interacting parts. Global patterns of biological diversity are complex. This biocomplexity stems from the interplay among ecological processes that influence patterns at different scales, such as transitional areas or ecotones spanning landscapes. Complexity stems from the interplay among levels of biological organization as energy, and matter is integrated into larger units that superimpose onto the smaller parts. Small scale patterns do not necessarily explain larger ones, as in Aristotle's expression "the sum is greater than the parts". "Complexity in ecology is of at least six distinct types: spatial, temporal, structural, process, behavioral, and geometric." From these principles, ecologists have identified emergent and self-organizing phenomena that operate at different environmental scales of influence, ranging from molecular to planetary, and these require different explanations at each integrative level. Holism Holism is a critical part of the theory of ecology. Holism addresses the biological organization of life that self-organizes into layers of emergent whole systems that function according to non-reducible properties. This means that higher-order patterns of a whole functional system, such as an ecosystem, cannot be predicted or understood by a simple summation of the parts. "New properties emerge because the components interact, not because the basic nature of the components is changed." == Relation to evolution ==

Ecology and evolutionary biology are sister disciplines. Natural selection, life history, development, adaptation, populations, and inheritance thread equally into both. In this framework, the analytical tools of ecologists and evolutionists overlap as they study life through phylogenetics or Linnaean taxonomy. Behavioural ecology (Bradypodion spp.). Chameleons change their skin colour to match their background as a behavioural defence mechanism and also use colour to communicate with other members of their species, such as dominant (left) versus submissive (right) patterns shown in the three species (A-C) above. Behaviours can be recorded as traits and inherited in much the same way that eye and hair colour can. Behaviours can evolve by means of natural selection as adaptive traits conferring functional utilities that increases reproductive fitness. "Until recently, however, cognitive scientists have not paid sufficient attention to the fundamental fact that cognitive traits evolved under particular natural settings. With consideration of the selection pressure on cognition, cognitive ecology can contribute intellectual coherence to the multidisciplinary study of cognition." Social ecology Social-ecological behaviours are notable in the social insects, slime moulds, social spiders, human society, and naked mole-rats where eusocialism has evolved. Social behaviours include reciprocally beneficial behaviours among kin and nest mates Biogeography and ecology share many of their disciplinary roots. Island biogeography, published by Robert MacArthur and Edward O. Wilson in 1967, Molecular ecology uses analytical techniques to study genes in an evolutionary and ecological context. In 1994, John Avise played a leading role in this area of science with the publication of his book, Molecular Markers, Natural History and Evolution. == Human ecology ==

A dual discipline {{quote box Ecology is both a biological science and a human science. == Relation to the environment ==

The environment of ecosystems includes both physical parameters and biotic attributes. It is dynamically interlinked and contains resources for organisms at any time throughout their life cycle. Biogeochemistry and climate Ecologists study nutrient budgets to understand how these materials are regulated, flow, and recycled through the environment. This research has led to an understanding that there is global feedback between ecosystems and the physical parameters of this planet, including minerals, soil, pH, ions, water, and atmospheric gases. Six major elements (hydrogen, carbon, nitrogen, oxygen, sulfur, and phosphorus; H, C, N, O, S, and P) 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 of ecological processes amplify and regulate the biogeochemical cycles of the Earth. == History ==

Early beginnings {{quote box Ecology has a complex origin. Ecological concepts such as a balance and regulation in nature can be traced to Herodotus (died c. 425 BC), who described mutualism in his observation of "natural dentistry". Basking Nile crocodiles, he noted, opened their mouths to give sandpipers safe access to pluck leeches out, giving nutrition to the sandpiper and oral hygiene for the crocodile. The term "ecology" () was coined by Ernst Haeckel in his book Generelle Morphologie der Organismen (1866). Haeckel was a zoologist, artist, writer, and later in life a professor of comparative anatomy. In the early 20th century, ecology transitioned from description to a more analytical form of scientific natural history. Frederic Clements published the first American ecology book, Research Methods in Ecology in 1905, presenting the idea of plant communities as a superorganism. This launched a debate between ecological holism and individualism that lasted until the 1970s. {{quote box Ecology surged in popular and scientific interest during the 1960–1970s environmental movement. == See also ==