In biology and ecology, abiotic components or abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Abiotic factors and the phenomena associated with them underpin all biology.
Abiotic components include physical conditions and non-living resources that affect living organisms in terms of growth, maintenance, and reproduction. Resources are distinguished as substances or objects in the environment required by one organism and consumed or otherwise made unavailable for use by other organisms.
Component degradation of a substance occurs by chemical or physical processes, e.g. hydrolysis. All non-living components of an ecosystem, such as atmospheric conditions and water resources, are called abiotic components.
In biology, abiotic factors can include water, light, radiation, temperature, humidity, atmosphere, and soil. The macroscopic climate often influences each of the above. Pressure and sound waves may also be considered in the context of marine or sub-terrestrial environments. Abiotic factors in ocean environments also include aerial exposure, substrate, water clarity, solar energy and tides. Consider the differences in the mechanics of C3, C4, and CAM plants in regulating the influx of carbon dioxide to the Calvin-Benson Cycle in relation to their abiotic stressors. C3 plants have no mechanisms to manage photorespiration, whereas C4 and CAM plants utilize a separate PEP Carboxylase enzyme to prevent photorespiration, thus increasing the yield of photosynthetic processes in certain high energy environments.
Many Archea require very high temperatures, pressures or unusual concentrations of chemical substances such as sulfur; this is due to their specialization into extreme conditions. In addition, fungi have also evolved to survive at the temperature, the humidity, and stability of their environment.
For example, there is a significant difference in access in both water and humidity between temperate rain forests and deserts. This difference in water availability causes a diversity in the organisms that survive in these areas. These differences in abiotic components alter the species present both by creating boundaries of what species can survive within the environment, as well as influencing competition between two species. Abiotic factors such as salinity can give one species a competitive advantage over another, creating pressures that lead to speciation and alteration of a species to and from generalist and specialist competitors.
An ecological cascade effect is a series of secondary extinctions that is triggered by the primary extinction of a key species in an ecosystem. Secondary extinctions are likely to occur when the threatened species are: dependent on a few specific food sources, mutualistic (dependent on the key species in some way), or forced to coexist with an invasive species that is introduced to the ecosystem. Species introductions to a foreign ecosystem can often devastate entire communities, and even entire ecosystems. These exotic species monopolize the ecosystem's resources, and since they have no natural predators to decrease their growth, they are able to increase indefinitely. Olsen et al. showed that exotic species have caused lake and estuary ecosystems to go through cascade effects due to loss of algae, crayfish, mollusks, fish, amphibians, and birds. However, the principal cause of cascade effects is the loss of top predators as the key species. As a result of this loss, a dramatic increase (ecological release) of prey species occurs. The prey is then able to overexploit its own food resources, until the population numbers decrease in abundance, which can lead to extinction. When the prey's food resources disappear, they starve and may go extinct as well. If the prey species is herbivorous, then their initial release and exploitation of the plants may result in a loss of plant biodiversity in the area. If other organisms in the ecosystem also depend upon these plants as food resources, then these species may go extinct as well. An example of the cascade effect caused by the loss of a top predator is apparent in tropical forests. When hunters cause local extinctions of top predators, the predators' prey's population numbers increase, causing an overexploitation of a food resource and a cascade effect of species loss. Recent studies have been performed on approaches to mitigate extinction cascades in food-web networks.Chemical ecology
Chemical ecology examines the role of chemical interactions between living organisms and their environment, and the consequences of those interactions on the ethology and evolution of the organisms involved. It is thus a vast and highly interdisciplinary field. Chemical ecology studies focus on the biochemistry of ecology and the specific molecules or groups of molecules that function as signals to initiate, modulate, or terminate a variety of biological processes such as metabolism. Molecules that serve in such roles typically are readily diffusible organic substances of low molecular mass that derive from secondary metabolic pathways, but also include peptides. Chemical ecological processes mediated by semiochemicals may be intraspecific (occurring within a species) or interspecific (occurring between species).The field relies on analytical and synthetic chemistry, protein chemistry, genetics, neurobiology, ecology, and evolution.Energy flow (ecology)
In ecology, energy flow, also called the calorific flow, refers to the flow of energy through a food chain, and is the focus of study in ecological energetics. In an ecosystem, ecologists seek to quantify the relative importance of different component species and feeding relationships.
A general energy flow scenario follows:
Solar energy is fixed by the photoautotrophs, called primary producers, like green plants. Primary consumers absorb most of the stored energy in the plant through digestion, and transform it into the form of energy they need, such as adenosine triphosphate (ATP), through respiration. A part of the energy received by primary consumers, herbivores, is converted to body heat (an effect of respiration), which is radiated away and lost from the system. The loss of energy through body heat is far greater in warm-blooded animals, which must eat much more frequently than those that are cold-blooded. Energy loss also occurs in the expulsion of undigested food (egesta) by excretion or regurgitation.
Secondary consumers, carnivores, then consume the primary consumers, although omnivores also consume primary producers. Energy that had been used by the primary consumers for growth and storage is thus absorbed into the secondary consumers through the process of digestion. As with primary consumers, secondary consumers convert this energy into a more suitable form (ATP) during respiration. Again, some energy is lost from the system, since energy which the primary consumers had used for respiration and regulation of body temperature cannot be utilized by the secondary consumers.
Tertiary consumers, which may or may not be apex predators, then consume the secondary consumers, with some energy passed on and some lost, as with the lower levels of the food chain.
A final link in the food chain are decomposers which break down the organic matter of the tertiary consumers (or whichever consumer is at the top of the chain) and release nutrients into the soil. They also break down plants, herbivores and carnivores that were not eaten by organisms higher on the food chain, as well as the undigested food that is excreted by herbivores and carnivores. Saprotrophic bacteria and fungi are decomposers, and play a pivotal role in the nitrogen and carbon cycles.The energy is passed on from trophic level to trophic level and each time about 90% of the energy is lost, with some being lost as heat into the environment (an effect of respiration) and some being lost as incompletely digested food (egesta). Therefore, primary consumers get about 10% of the energy produced by autotrophs, while secondary consumers get 1% and tertiary consumers get 0.1%. This means the top consumer of a food chain receives the least energy, as a lot of the food chain's energy has been lost between trophic levels. This loss of energy at each level limits typical food chains to only four to six links.Food web
A food web (or food cycle) is the natural interconnection of food chains and a graphical representation (usually an image) of what-eats-what in an ecological community. Another name for food web is consumer-resource system. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs. To maintain their bodies, grow, develop, and to reproduce, autotrophs produce organic matter from inorganic substances, including both minerals and gases such as carbon dioxide. These chemical reactions require energy, which mainly comes from the Sun and largely by photosynthesis, although a very small amount comes from hydrothermal vents and hot springs. A gradient exists between trophic levels running from complete autotrophs that obtain their sole source of carbon from the atmosphere, to mixotrophs (such as carnivorous plants) that are autotrophic organisms that partially obtain organic matter from sources other than the atmosphere, and complete heterotrophs that must feed to obtain organic matter. The linkages in a food web illustrate the feeding pathways, such as where heterotrophs obtain organic matter by feeding on autotrophs and other heterotrophs. The food web is a simplified illustration of the various methods of feeding that links an ecosystem into a unified system of exchange. There are different kinds of feeding relations that can be roughly divided into herbivory, carnivory, scavenging and parasitism. Some of the organic matter eaten by heterotrophs, such as sugars, provides energy. Autotrophs and heterotrophs come in all sizes, from microscopic to many tonnes - from cyanobacteria to giant redwoods, and from viruses and bdellovibrio to blue whales.
Charles Elton pioneered the concept of food cycles, food chains, and food size in his classical 1927 book "Animal Ecology"; Elton's 'food cycle' was replaced by 'food web' in a subsequent ecological text. Elton organized species into functional groups, which was the basis for Raymond Lindeman's classic and landmark paper in 1942 on trophic dynamics. Lindeman emphasized the important role of decomposer organisms in a trophic system of classification. The notion of a food web has a historical foothold in the writings of Charles Darwin and his terminology, including an "entangled bank", "web of life", "web of complex relations", and in reference to the decomposition actions of earthworms he talked about "the continued movement of the particles of earth". Even earlier, in 1768 John Bruckner described nature as "one continued web of life".
Food webs are limited representations of real ecosystems as they necessarily aggregate many species into trophic species, which are functional groups of species that have the same predators and prey in a food web. Ecologists use these simplifications in quantitative (or mathematical representation) models of trophic or consumer-resource systems dynamics. Using these models they can measure and test for generalized patterns in the structure of real food web networks. Ecologists have identified non-random properties in the topographic structure of food webs. Published examples that are used in meta analysis are of variable quality with omissions. However, the number of empirical studies on community webs is on the rise and the mathematical treatment of food webs using network theory had identified patterns that are common to all. Scaling laws, for example, predict a relationship between the topology of food web predator-prey linkages and levels of species richness.Glossary of biology
Most of the terms listed in Wikipedia glossaries are already defined and explained within Wikipedia itself. However, glossaries like this one are useful for looking up, comparing and reviewing large numbers of terms together. You can help enhance this page by adding new terms or writing definitions for existing ones.
This glossary of biology terms is a list of definitions of fundamental terms and concepts of biology, its sub-disciplines, and related fields. For more specific definitions from other glossaries related to biology, see Glossary of ecology, Glossary of botany, Glossary of genetics, and Glossary of speciation.Glossary of ecology
This glossary of ecology is a list of definitions of terms and topics in ecology and related fields. For more specific definitions from other glossaries related to ecology, see Glossary of biology and Glossary of environmental science.Invasive species
An invasive species is a species that is not native to a specific location (an introduced species), and that has a tendency to spread to a degree believed to cause damage to the environment, human economy or human health.The term as most often used applies to introduced species that adversely affect the habitats and bioregions they invade economically, environmentally, or ecologically. Such species may be either plants or animals and may disrupt by dominating a region, wilderness areas, particular habitats, or wildland–urban interface land from loss of natural controls (such as predators or herbivores). This includes plant species labeled as exotic pest plants and invasive exotics growing in native plant communities. The European Union defines "Invasive Alien Species" as those that are, firstly, outside their natural distribution area, and secondly, threaten biological diversity. The term is also used by land managers, botanists, researchers, horticulturalists, conservationists, and the public for noxious weeds.The term "invasive" is often poorly defined or very subjective and some broaden the term to include indigenous or "native" species, that have colonized natural areas - for example deer considered by some to be overpopulating their native zones and adjacent suburban gardens in the Northeastern and Pacific Coast regions of the United States.The definition of "native" is also sometimes controversial. For example, the ancestors of Equus ferus (modern horses) evolved in North America and radiated to Eurasia before becoming locally extinct. Upon returning to North America in 1493 during their hominid-assisted migration, it is debatable as to whether they were native or exotic to the continent of their evolutionary ancestors.Notable examples of invasive plant species include the kudzu vine, Andean pampas grass, and yellow starthistle. Animal examples include the New Zealand mud snail, feral pigs, European rabbits, grey squirrels, domestic cats, carp and ferrets.Invasion of long-established ecosystems by organisms from distant bio-regions is a natural phenomenon, but has been accelerated massively by humans, from their earliest migrations though to the age of discovery, and now international trade.Limiting factor
A limiting factor is a variable of a system that, if subject to a small change, causes a non-negligible change in an output or other measure of the system. A factor not limiting over a certain domain of starting conditions may yet be limiting over another domain of starting conditions, including that of the factor.Limnoforming
Limnoforming (from Greek: limnee, "lake"; Latin: formocode: lat promoted to code: la , "to shape", as in shaping, fashioning, molding, modeling) is the process of manipulating the physical or chemical properties of a body of water by introducing organisms which facilitate higher level biological activity, thus impacting the overall ecology of a given body of water, and eventually adjacent ecosystems.
Limnoforming is a process using living organisms to enhance a habitat's abiotic component, ultimately rendering it more conducive to a higher ecological quality. This could be accomplished by introducing a population of organisms, e.g., invertebrates or microbes, en masse to the substrate of a body of water. These organisms would then physically and/or chemically alter the underwater environment to furnish a more suitable substrate for a wider range of biological activity; the result being an increased ecological function (e.g., in trophic dynamics), and thus a higher quality ecological state. Ultimately, limnoforming aims to accelerate the rate of ecological succession in distressed aquatic systems (e.g., lower Green Bay, Lake Michigan), so as to produce a biologically complex climax community in a comparatively short amount of time.
The concept of limnoforming originated from the benthic ecology laboratory of Dr. Jerry L. Kaster, School of Freshwater Sciences, University of Wisconsin – Milwaukee. Limnoforming was partially inspired by, and is similar in several aspects to, the concept of terraforming. The two concepts' main similarity is that both aim to accelerate the rate of change occurring in a given environment, in terms of its habitability for a given species or for a number of species, and furthermore, the overall function of its ecology. Instead of creating a habitable ecosystem or biosphere from scratch, limnoforming simply aims to amend degraded earthly aqueous environments less apt to harboring a high quality ecological community into an environment which does support an ecologically flourishing system. Limnoforming differs from traditional habitat rehabilitation or restoration in that limnoforming is driven by an early sere biological succession process that modifies the physical substrate making it better suited for later seres, whereas rehabilitation/restoration is generally driven by targeting a terminal sere that is poorly adapted at re-forming habitat upon which it depends.
The initial limnoforming study, in Green Bay, Lake Michigan, uses freshwater oligochaetes to re-consolidate highly fluid gyttja substrate (organic black ooze) found extensively in lower Green Bay. The goal is to modify substrate suitability for the mayfly Hexagenia. Historically, this mayfly was found in abundance but the eutrophication of the bay led to their demise in first half of the 20th century.Mesopredator release hypothesis
The mesopredator release hypothesis is an ecological theory used to describe the interrelated population dynamics between apex predators and mesopredators within an ecosystem, such that a collapsing population of the former results in dramatically-increased populations of the latter. This hypothesis describes the phenomenon of trophic cascade in specific terrestrial communities.
A mesopredator is a medium-sized, middle trophic level predator, which both preys and is preyed upon. Examples are raccoons, skunks, snakes, cownose rays, and small sharks.Outline of agriculture
The following outline is provided as an overview of and topical guide to agriculture:
Agriculture – cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life.Productivity (ecology)
In ecology, productivity refers to the rate of generation of biomass in an ecosystem. It is usually expressed in units of mass per unit surface (or volume) per unit time, for instance grams per square metre per day (g m−2 d−1). The mass unit may relate to dry matter or to the mass of carbon generated. Productivity of autotrophs such as plants is called primary productivity, while that of heterotrophs such as animals is called secondary productivity.Resource (biology)
In Biology and Ecology, a resource is a substance or object in the environment required by an organism for normal growth, maintenance, and reproduction. Resources can be consumed by one organism and, as a result, become unavailable to another organism. For plants key resources are light, nutrients, water, and place to grow. For animals key resources are food, water, and territory.Soil carbon
Soil carbon includes both inorganic carbon as carbonate minerals, and as soil organic matter. Soil carbon plays a key role in the carbon cycle, and thus it is important in global climate models.Sustainable gardening
Sustainable gardening includes the more specific sustainable landscapes, sustainable landscape design, sustainable landscaping, sustainable landscape architecture, resulting in sustainable sites. It comprises a disparate group of horticultural interests that can share the aims and objectives associated with the international post-1980s sustainable development and sustainability programs developed to address the fact that humans are now using natural biophysical resources faster than they can be replenished by nature.Included within this compass are those home gardeners, and members of the landscape and nursery industries, and municipal authorities, that integrate environmental, social, and economic factors to create a more sustainable future.
Organic gardening and the use of native plants are integral to sustainable gardening.