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121-463: The EcoLeague offers studies in ecology , conservation biology , marine biology , and natural and cultural history interpretation, sustainable business . The consortium is unique in that each college is in a different geographic area. Despite a wide variation in structure and culture, the five colleges have strong programs in environmental studies . The idea behind the consortium is the ability to experience learning in virtually every major biome of

242-484: A final cause (a purpose), but thought that it "came about naturally, since such things survived." Aristotle did believe in final causes, but assumed that species were fixed . In natural theology , adaptation was interpreted as the work of a deity and as evidence for the existence of God. William Paley believed that organisms were perfectly adapted to the lives they led, an argument that shadowed Gottfried Wilhelm Leibniz , who had argued that God had brought about "

363-441: A neuropsychological capacity for learning . Examples include searching for food , mating , and vocalizations . Physiological adaptations permit the organism to perform special functions such as making venom , secreting slime , and phototropism , but also involve more general functions such as growth and development , temperature regulation , ionic balance and other aspects of homeostasis . Adaptation affects all aspects of

484-465: A dramatic effect on community structure. Hunting of sea otters, for example, is thought to have led indirectly to the extinction of the Steller's sea cow ( Hydrodamalis gigas ). While the keystone species concept has been used extensively as a conservation tool, it has been criticized for being poorly defined from an operational stance. It is difficult to experimentally determine what species may hold

605-428: A dramatic impact on the ecology of individual species or whole ecosystems. For instance, the replacement of an ant species by another (invasive) ant species has been shown to affect how elephants reduce tree cover and thus the predation of lions on zebras . A trophic level (from Greek troph , τροφή, trophē, meaning "food" or "feeding") is "a group of organisms acquiring a considerable majority of its energy from

726-412: A flattened body relative to the main populations that live in open savanna. The population that lives in an isolated rock outcrop hides in crevasses where its flattened body offers a selective advantage. Habitat shifts also occur in the developmental life history of amphibians, and in insects that transition from aquatic to terrestrial habitats. Biotope and habitat are sometimes used interchangeably, but

847-526: A great deal of genetic variability. The first experimental evidence of the pre-adaptive nature of genetic variants in microorganisms was provided by Salvador Luria and Max Delbrück who developed the Fluctuation Test , a method to show the random fluctuation of pre-existing genetic changes that conferred resistance to bacteriophages in Escherichia coli . The word is controversial because it

968-427: A higher fecundity and broader geographic range. The peacock 's ornamental train (grown anew in time for each mating season) is a famous adaptation. It must reduce his maneuverability and flight, and is hugely conspicuous; also, its growth costs food resources. Darwin's explanation of its advantage was in terms of sexual selection : "This depends on the advantage which certain individuals have over other individuals of

1089-612: A higher one." Small scale patterns do not necessarily explain large scale phenomena, otherwise captured in the expression (coined by Aristotle) '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 . Ecological complexity relates to

1210-444: A keystone role in each ecosystem. Furthermore, food web theory suggests that keystone species may not be common, so it is unclear how generally the keystone species model can be applied. Complexity is understood as a large computational effort needed to piece together numerous interacting parts exceeding the iterative memory capacity of the human mind. Global patterns of biological diversity are complex. This biocomplexity stems from

1331-408: A keystone species can result in a community collapse just as the removal of the keystone in an arch can result in the arch's loss of stability. Sea otters ( Enhydra lutris ) are commonly cited as an example of a keystone species 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

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1452-741: A legacy niche that was constructed before their time. Biomes are larger units of organization that categorize regions of the Earth's ecosystems, mainly according to the structure and composition of vegetation. There are different methods to define the continental boundaries of biomes dominated by different functional types of vegetative communities that are limited in distribution by climate, precipitation, weather, and other environmental variables. Biomes include tropical rainforest , temperate broadleaf and mixed forest , temperate deciduous forest , taiga , tundra , hot desert , and polar desert . Other researchers have recently categorized other biomes, such as

1573-439: A linear successional route, changes might occur quickly or slowly over thousands of years before specific forest successional stages are brought about by biological processes. An ecosystem's area can vary greatly, 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. Several generations of an aphid population can exist over

1694-439: A macroscopic view of the system. While the notion of trophic levels provides insight into energy flow and top-down control within food webs, it is troubled by the prevalence of omnivory in real ecosystems. This has led some ecologists to "reiterate that the notion that species clearly aggregate into discrete, homogeneous trophic levels is fiction." Nonetheless, recent studies have shown that real trophic levels do exist, but "above

1815-423: A mechanism whose significance had only been glimpsed previously. A century later, experimental field studies and breeding experiments by people such as E. B. Ford and Theodosius Dobzhansky produced evidence that natural selection was not only the 'engine' behind adaptation, but was a much stronger force than had previously been thought. The significance of an adaptation can only be understood in relation to

1936-516: A mix of herbivores and predators). Omnivores do not fit neatly into a functional category because they eat both plant and animal tissues. It has been suggested that omnivores have a greater functional influence as predators because compared to herbivores, they are relatively inefficient at grazing. Trophic levels are part of the holistic or complex systems view of ecosystems. Each trophic level contains unrelated species that are grouped together because they share common ecological functions, giving

2057-420: A new appreciation for the influence that organisms have on the ecosystem and evolutionary process. The term "niche construction" is more often used in reference to the under-appreciated feedback mechanisms of natural selection imparting forces on the abiotic niche. An example of natural selection through ecosystem engineering occurs in the nests of social insects , including ants, bees, wasps, and termites. There

2178-457: A niche for ectoparasites ; the only flying penguins do is under water. Adaptations serving different functions may be mutually destructive. Compromise and makeshift occur widely, not perfection. Selection pressures pull in different directions, and the adaptation that results is some kind of compromise. It is a profound truth that Nature does not know best; that genetical evolution... is a story of waste, makeshift, compromise and blunder. Since

2299-435: A population-level phenomenon, as with the migration routes followed by plants as they occupied northern post-glacial environments. Plant ecologists use pollen records that accumulate and stratify in wetlands to reconstruct the timing of plant migration and dispersal relative to historic and contemporary climates. These migration routes involved an expansion of the range as plant populations expanded from one area to another. There

2420-401: A region), and sites are classed either as sources or sinks. A site is a generic term that refers to places where ecologists sample populations, such as ponds or defined sampling areas in a forest. Source patches are productive sites that generate a seasonal supply of juveniles that migrate to other patch locations. Sink patches are unproductive sites that only receive migrants; the population at

2541-517: A seasonal influx of new immigrants. A dynamic metapopulation structure evolves from year to year, where some patches are sinks in dry years and are sources when conditions are more favorable. Ecologists use a mixture of computer models and field studies to explain metapopulation structure. Community ecology examines how interactions among species and their environment affect the abundance, distribution and diversity of species within communities. Johnson & Stinchcomb (2007) Community ecology

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2662-426: A similar problem. As another example, the long neck of a giraffe brings benefits but at a cost. The neck of a giraffe can be up to 2 m (6 ft 7 in) in length. The benefits are that it can be used for inter-species competition or for foraging on tall trees where shorter herbivores cannot reach. The cost is that a long neck is heavy and adds to the animal's body mass, requiring additional energy to build

2783-456: A species describes the environment over which a species is known to occur and the type of community that is formed as a result. More specifically, "habitats can be defined as regions in environmental space that are composed of multiple dimensions, each representing a biotic or abiotic environmental variable; that is, any component or characteristic of the environment related directly (e.g. forage biomass and quality) or indirectly (e.g. elevation) to

2904-402: A specific habitat, such as a cave or a pond, and principles gleaned from small-scale studies are extrapolated to larger systems. Feeding relations require extensive investigations, e.g. into the gut contents of organisms, which can be difficult to decipher, or stable isotopes can be used to trace the flow of nutrient diets and energy through a food web. Despite these limitations, food webs remain

3025-411: A trait, whereas fitness predicts a trait's future. Sewall Wright proposed that populations occupy adaptive peaks on a fitness landscape. To evolve to another, higher peak, a population would first have to pass through a valley of maladaptive intermediate stages, and might be "trapped" on a peak that is not optimally adapted. Adaptation is the heart and soul of evolution. Before Darwin, adaptation

3146-446: A valuable tool in understanding community ecosystems. Food webs illustrate important principles of ecology : some species have many weak feeding links (e.g., omnivores ) while some are more specialized with fewer stronger feeding links (e.g., primary predators ). Such linkages explain how ecological communities remain stable over time and eventually can illustrate a "complete" web of life. The disruption of food webs may have

3267-598: A way that suits the habitat. The varying shapes of the beaks of Darwin's finches, for example, are driven by adaptive mutations in the ALX1 gene. The coat color of different wild mouse species matches their environments, whether black lava or light sand, owing to adaptive mutations in the melanocortin 1 receptor and other melanin pathway genes. Physiological resistance to the heart poisons ( cardiac glycosides ) that monarch butterflies store in their bodies to protect themselves from predators are driven by adaptive mutations in

3388-1593: 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." Adaptation Collective intelligence Collective action Self-organized criticality Herd mentality Phase transition Agent-based modelling Synchronization Ant colony optimization Particle swarm optimization Swarm behaviour Social network analysis Small-world networks Centrality Motifs Graph theory Scaling Robustness Systems biology Dynamic networks Evolutionary computation Genetic algorithms Genetic programming Artificial life Machine learning Evolutionary developmental biology Artificial intelligence Evolutionary robotics Reaction–diffusion systems Partial differential equations Dissipative structures Percolation Cellular automata Spatial ecology Self-replication Conversation theory Entropy Feedback Goal-oriented Homeostasis Information theory Operationalization Second-order cybernetics Self-reference System dynamics Systems science Systems thinking Sensemaking Variety Ordinary differential equations Phase space Attractors Population dynamics Chaos Multistability Bifurcation Rational choice theory Bounded rationality In biology , adaptation has three related meanings. Firstly, it

3509-399: A wide array of interacting levels of organization spanning micro-level (e.g., cells ) to a planetary scale (e.g., biosphere ) phenomena . Ecosystems, for example, contain abiotic resources and interacting life forms (i.e., individual organisms that aggregate into populations which aggregate into distinct ecological communities). Because ecosystems are dynamic and do not necessarily follow

3630-424: Is teleological and the entire concept of natural selection depends on the presence of genetic variation, regardless of the population size of a species in question. Features that now appear as adaptations sometimes arose by co-option of existing traits, evolved for some other purpose. The classic example is the ear ossicles of mammals , which we know from paleontological and embryological evidence originated in

3751-485: Is a central concept in the ecology of organisms and is sub-divided into the fundamental and the realized niche. The fundamental niche is the set of environmental conditions under which a species is able to persist. The realized niche is the set of environmental plus ecological conditions under which a species persists. The Hutchinsonian niche is defined more technically as a " Euclidean hyperspace whose dimensions are defined as environmental variables and whose size

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3872-504: Is a function of the number of values that the environmental values may assume for which an organism has positive fitness ." Biogeographical patterns and range distributions are explained or predicted through knowledge of a species' traits and niche requirements. Species have functional traits that are uniquely adapted to the ecological niche. A trait is a measurable property, phenotype , or characteristic of an organism that may influence its survival. Genes play an important role in

3993-414: Is a larger taxonomy of movement, such as commuting, foraging, territorial behavior, stasis, and ranging. Dispersal is usually distinguished from migration because it involves the one-way permanent movement of individuals from their birth population into another population. In metapopulation terminology, migrating individuals are classed as emigrants (when they leave a region) or immigrants (when they enter

4114-523: Is a major topic in the philosophy of biology , as it concerns function and purpose ( teleology ). Some biologists try to avoid terms which imply purpose in adaptation, not least because it suggests a deity's intentions, but others note that adaptation is necessarily purposeful. Adaptation is an observable fact of life accepted by philosophers and natural historians from ancient times, independently of their views on evolution , but their explanations differed. Empedocles did not believe that adaptation required

4235-461: Is an emergent homeostasis or homeorhesis in the structure of the nest that regulates, maintains and defends the physiology of the entire colony. Termite mounds, for example, maintain a constant internal temperature through the design of air-conditioning chimneys. The structure of the nests themselves is subject to the forces of natural selection. Moreover, a nest can survive over successive generations, so that progeny inherit both genetic material and

4356-404: Is another statistical approach that is often used in conservation research . Metapopulation models simplify the landscape into patches of varying levels of quality, and metapopulations are linked by the migratory behaviours of organisms. Animal migration is set apart from other kinds of movement because it involves the seasonal departure and return of individuals from a habitat. Migration is also

4477-408: Is better fitted to survive in the new environment," writes the evolutionary biologist John Maynard Smith . If humans move to a higher altitude, respiration and physical exertion become a problem, but after spending time in high altitude conditions they acclimatize to the reduced partial pressure of oxygen, such as by producing more red blood cells . The ability to acclimatize is an adaptation, but

4598-558: Is called habitat tracking . It is one explanation put forward for the periods of apparent stasis in the fossil record (the punctuated equilibrium theory). Without mutation , the ultimate source of all genetic variation , there would be no genetic changes and no subsequent adaptation through evolution by natural selection. Genetic change occurs in a population when mutation increases or decreases in its initial frequency followed by random genetic drift, migration, recombination or natural selection act on this genetic variation. One example

4719-438: Is greater than respiration) by photosynthesis or chemosynthesis . Heterotrophs are organisms that must feed on others for nourishment and energy (respiration exceeds production). Heterotrophs can be further sub-divided into different functional groups, including primary consumers (strict herbivores), secondary consumers ( carnivorous predators that feed exclusively on herbivores), and tertiary consumers (predators that feed on

4840-506: Is that the first pathways of enzyme-based metabolism at the very origin of life on Earth may have been co-opted components of the already-existing purine nucleotide metabolism , a metabolic pathway that evolved in an ancient RNA world . The co-option requires new mutations and through natural selection, the population then adapts genetically to its present circumstances. Genetic changes may result in entirely new or gradual change to visible structures, or they may adjust physiological activity in

4961-590: Is the Park Grass Experiment , which was initiated in 1856. Another example is the Hubbard Brook study , which has been in operation since 1960. Holism remains a critical part of the theoretical foundation in contemporary ecological studies. 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

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5082-460: Is the natural science of the relationships among living organisms and their environment . Ecology considers organisms at the individual, population , community , ecosystem , and biosphere levels. Ecology overlaps with the closely related sciences of biogeography , evolutionary biology , genetics , ethology , and natural history . Ecology is a branch of biology , and is the study of abundance , biomass , and distribution of organisms in

5203-413: Is the biosphere: the total sum of ecosystems on the planet. Ecological relationships regulate the flux of energy, nutrients, and climate all the way up to the planetary scale. For example, the dynamic history of the planetary atmosphere's CO 2 and O 2 composition has been affected by the biogenic flux of gases coming from respiration and photosynthesis, with levels fluctuating over time in relation to

5324-440: Is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their evolutionary fitness . Secondly, it is a state reached by the population during that process. Thirdly, it is a phenotypic trait or adaptive trait , with a functional role in each individual organism , that is maintained and has evolved through natural selection. Historically, adaptation has been described from

5445-522: Is the evolution of cichlid fish in African lakes, where the question of reproductive isolation is complex. Adaptation is not always a simple matter where the ideal phenotype evolves for a given environment. An organism must be viable at all stages of its development and at all stages of its evolution. This places constraints on the evolution of development, behaviour, and structure of organisms. The main constraint, over which there has been much debate,

5566-766: Is the requirement that each genetic and phenotypic change during evolution should be relatively small, because developmental systems are so complex and interlinked. However, it is not clear what "relatively small" should mean, for example polyploidy in plants is a reasonably common large genetic change. The origin of eukaryotic endosymbiosis is a more dramatic example. All adaptations help organisms survive in their ecological niches . The adaptive traits may be structural, behavioural or physiological . Structural adaptations are physical features of an organism, such as shape, body covering, armament, and internal organization . Behavioural adaptations are inherited systems of behaviour, whether inherited in detail as instincts , or as

5687-522: Is the study of the interactions among a collection of species that inhabit the same geographic area. Community ecologists study the determinants of patterns and processes for two or more interacting species. Research in community ecology might measure species diversity in grasslands in relation to soil fertility. It might also include the analysis of predator-prey dynamics, competition among similar plant species, or mutualistic interactions between crabs and corals. These ecosystems, as we may call them, are of

5808-556: Is used for managing wildlife stocks and setting harvest quotas. In cases where basic models are insufficient, ecologists may adopt different kinds of statistical methods, such as the Akaike information criterion , or use models that can become mathematically complex as "several competing hypotheses are simultaneously confronted with the data." The concept of metapopulations was defined in 1969 as "a population of populations which go extinct locally and recolonize". Metapopulation ecology

5929-409: Is via the introduction of new genetic variation for natural selection to act upon. Seen like this, adaptation is a genetic tracking process , which goes on all the time to some extent, but especially when the population cannot or does not move to another, less hostile area. Given enough genetic change, as well as specific demographic conditions, an adaptation may be enough to bring a population back from

6050-464: Is what is now called Lamarckism , a proto-evolutionary hypothesis of the inheritance of acquired characteristics , intended to explain adaptations by natural means. Other natural historians, such as Buffon , accepted adaptation, and some also accepted evolution, without voicing their opinions as to the mechanism. This illustrates the real merit of Darwin and Alfred Russel Wallace , and secondary figures such as Henry Walter Bates , for putting forward

6171-609: The White Leghorn chicken is markedly more resistant to vitamin B 1 deficiency than other breeds; on a plentiful diet this makes no difference, but on a restricted diet this preadaptation could be decisive. Pre-adaptation may arise because a natural population carries a huge quantity of genetic variability. In diploid eukaryotes, this is a consequence of the system of sexual reproduction , where mutant alleles get partially shielded, for example, by genetic dominance . Microorganisms , with their huge populations, also carry

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6292-405: The abundance or biomass at each level. When the relative abundance or biomass of each species is sorted into its respective trophic level, they naturally sort into a 'pyramid of numbers'. 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

6413-492: The last glacial period presumably depended on the relative gain and loss of reproductive capacity in the population of elks during that time. As another example, camouflage to avoid detection is destroyed when vivid coloration is displayed at mating time. Here the risk to life is counterbalanced by the necessity for reproduction. Stream-dwelling salamanders, such as Caucasian salamander or Gold-striped salamander have very slender, long bodies, perfectly adapted to life at

6534-412: The life cycle , which is often quite complex. However, as a practical term, "adaptation" often refers to a product : those features of a species which result from the process. Many aspects of an animal or plant can be correctly called adaptations, though there are always some features whose function remains in doubt. By using the term adaptation for the evolutionary process , and adaptive trait for

6655-436: The logistic equation by Pierre Verhulst : where N(t) is the number of individuals measured as biomass density as a function of time, t , r is the maximum per-capita rate of change commonly known as the intrinsic rate of growth, and α {\displaystyle \alpha } is the crowding coefficient, which represents the reduction in population growth rate per individual added. The formula states that

6776-518: The warning coloration of aculeate Hymenoptera ( wasps and bees ). Such mimicry does not need to be perfect to improve the survival of the palatable species. Bates, Wallace and Fritz Müller believed that Batesian and Müllerian mimicry provided evidence for the action of natural selection , a view which is now standard amongst biologists. All adaptations have a downside: horse legs are great for running on grass, but they cannot scratch their backs; mammals ' hair helps temperature, but offers

6897-551: The Earth and atmospheric conditions within a narrow self-regulating range of tolerance. Population ecology studies the dynamics of species populations and how these populations interact with the wider environment. A population consists of individuals of the same species that live, interact, and migrate through the same niche and habitat. A primary law of population ecology is the Malthusian growth model which states, "a population will grow (or decline) exponentially as long as

7018-462: The United States, based on their mission of promoting a "bio-regional education for sustainability". The EcoLeague was founded as a result of a visionary call from students with a proposal improve academic collaboration and mobility related to urgent issues of global sustainability. The consortium design, including student and faculty exchange program and regular cross-college conferences,

7139-575: The ability of an organism with a given genotype (genetic type) to change its phenotype (observable characteristics) in response to changes in its habitat , or to move to a different habitat. The degree of flexibility is inherited, and varies between individuals. A highly specialized animal or plant lives only in a well-defined habitat, eats a specific type of food, and cannot survive if its needs are not met. Many herbivores are like this; extreme examples are koalas which depend on Eucalyptus , and giant pandas which require bamboo . A generalist, on

7260-402: The acclimatization itself is not. The reproductive rate declines, but deaths from some tropical diseases also go down. Over a longer period of time, some people are better able to reproduce at high altitudes than others. They contribute more heavily to later generations, and gradually by natural selection the whole population becomes adapted to the new conditions. This has demonstrably occurred, as

7381-427: The appearance and spread of corresponding features in the other species. In other words, each species triggers reciprocal natural selection in the other. These co-adaptational relationships are intrinsically dynamic, and may continue on a trajectory for millions of years, as has occurred in the relationship between flowering plants and pollinating insects. Bates' work on Amazonian butterflies led him to develop

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7502-401: The banks of fast small rivers and mountain brooks . Elongated body protects their larvae from being washed out by current. However, elongated body increases risk of desiccation and decreases dispersal ability of the salamanders; it also negatively affects their fecundity . As a result, fire salamander , less perfectly adapted to the mountain brook habitats, is in general more successful, have

7623-525: The best of all possible worlds ." Voltaire 's satire Dr. Pangloss is a parody of this optimistic idea, and David Hume also argued against design. Charles Darwin broke with the tradition by emphasising the flaws and limitations which occurred in the animal and plant worlds. Jean-Baptiste Lamarck proposed a tendency for organisms to become more complex, moving up a ladder of progress, plus "the influence of circumstances", usually expressed as use and disuse . This second, subsidiary element of his theory

7744-441: The bodily part or function (the product), one may distinguish the two different senses of the word. Adaptation is one of the two main processes that explain the observed diversity of species, such as the different species of Darwin's finches . The other process is speciation , in which new species arise, typically through reproductive isolation . An example widely used today to study the interplay of adaptation and speciation

7865-550: The brink of extinction in a process called evolutionary rescue . Adaptation does affect, to some extent, every species in a particular ecosystem . Leigh Van Valen thought that even in a stable environment, because of antagonistic species interactions and limited resources, a species must constantly had to adapt to maintain its relative standing. This became known as the Red Queen hypothesis , as seen in host- parasite interactions. Existing genetic variation and mutation were

7986-509: The completion of their degrees, hiring on board several faculty, and developing an area of the college (to be determined) to carry on the Green Mountain name. This article on a United States institution of higher education is a stub . You can help Misplaced Pages by expanding it . Ecology Ecology (from Ancient Greek οἶκος ( oîkos )  'house' and -λογία ( -logía )  'study of')

8107-722: The consortium. Former consortium members included Antioch College , Green Mountain College , Naropa University , Sterling College , Unity College and Warren Wilson College , and Audubon Expedition Institute. In 2019, Green Mountain College in Poultney, Vermont (formally a member of the EcoLeague) announced it would be closing at the end of the spring semester, reducing the consortium down to five colleges. Green Mountain concurrently announced an agreement with Prescott College (an EcoLeague colleague) to support their students through

8228-744: The context of the environment. It encompasses life processes, interactions, and adaptations ; movement of materials and energy through living communities; successional development of ecosystems; cooperation, competition, and predation within and between species ; and patterns of biodiversity and its effect on ecosystem processes. Ecology has practical applications in conservation biology , wetland management, natural resource management ( agroecology , agriculture , forestry , agroforestry , fisheries , mining , tourism ), urban planning ( urban ecology ), community health , economics , basic and applied science , and human social interaction ( human ecology ). The word ecology ( German : Ökologie )

8349-714: The diversity of life from genes to ecosystems and spans every level of biological organization. The term has several interpretations, and there are many ways to index, measure, characterize, and represent its complex organization. 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. Biodiversity plays an important role in ecosystem services which by definition maintain and improve human quality of life. Conservation priorities and management techniques require different approaches and considerations to address

8470-530: The dynamic resilience of ecosystems that transition to multiple shifting steady-states directed by random fluctuations of history. Long-term ecological studies provide important track records to better understand the complexity and resilience of ecosystems over longer temporal and broader spatial scales. These studies are managed by the International Long Term Ecological Network (LTER). The longest experiment in existence

8591-456: The ecology and evolution of plants and animals. Ecological theory has also been used to explain self-emergent regulatory phenomena at the planetary scale: for example, the Gaia hypothesis is an example of holism applied in ecological theory. The Gaia hypothesis states that there is an emergent feedback loop generated by the metabolism of living organisms that maintains the core temperature of

8712-477: The ecosystems of the valleys around them. Earthworms, as Darwin noted, improve the topsoil in which they live by incorporating organic matter. Humans have constructed extensive civilizations with cities in environments as varied as the Arctic and hot deserts. In all three cases, the construction and maintenance of ecological niches helps drive the continued selection of the genes of these animals, in an environment that

8833-434: 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 that is used to illustrate and study pathways of energy and material flows. Empirical measurements are generally restricted to

8954-460: The environment experienced by all individuals in the population remains constant." Simplified population models usually starts with four variables: death, birth, immigration , and emigration . An example of an introductory population model describes a closed population, such as on an island, where immigration and emigration does not take place. Hypotheses are evaluated with reference to a null hypothesis which states that random processes create

9075-451: The equilibrium, r / α {\displaystyle r/\alpha } as K , which is known as the "carrying capacity." Population ecology builds upon these introductory models to further understand demographic processes in real study populations. Commonly used types of data include life history , fecundity , and survivorship, and these are analyzed using mathematical techniques such as matrix algebra . The information

9196-465: The first scientific account of mimicry , especially the kind of mimicry which bears his name: Batesian mimicry . This is the mimicry by a palatable species of an unpalatable or noxious species (the model), gaining a selective advantage as predators avoid the model and therefore also the mimic. Mimicry is thus an anti-predator adaptation . A common example seen in temperate gardens is the hoverfly (Syrphidae), many of which—though bearing no sting—mimic

9317-589: The flux of energy and matter through an environment. Ecosystems have biophysical feedback mechanisms that moderate processes acting on living ( biotic ) and abiotic components of the planet. Ecosystems sustain life-supporting functions and provide ecosystem services like biomass production (food, fuel, fiber, and medicine), the regulation of climate , global biogeochemical cycles , water filtration , soil formation , erosion control, flood protection, and many other natural features of scientific, historical, economic, or intrinsic value. The scope of ecology contains

9438-400: The former applies to a community's environment, whereas the latter applies to a species' environment. Definitions of the niche date back to 1917, but G. Evelyn Hutchinson made conceptual advances in 1957 by introducing a widely adopted definition: "the set of biotic and abiotic conditions in which a species is able to persist and maintain stable population sizes." The ecological niche

9559-544: The former relates only to the physical modifications of the habitat whereas the latter also considers the evolutionary implications of physical changes to the environment and the feedback this causes on the process of natural selection. 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." The ecosystem engineering concept has stimulated

9680-518: The full ecological scope of biodiversity. Natural capital that supports populations is critical for maintaining ecosystem services and species migration (e.g., riverine fish runs and avian insect control) has been implicated as one mechanism by which those service losses are experienced. An understanding of biodiversity has practical applications for species and ecosystem-level conservation planners as they make management recommendations to consulting firms, governments, and industry. The habitat of

9801-408: The herbivore trophic level, food webs are better characterized as a tangled web of omnivores." A keystone species is a species that is connected to a disproportionately large number of other species in the food-web . Keystone species have lower levels of biomass in the trophic pyramid relative to the importance of their role. The many connections that a keystone species holds means that it maintains

9922-406: The human and oceanic microbiomes . To a microbe , the human body is a habitat and a landscape. Microbiomes were discovered largely through advances in molecular genetics , which have revealed a hidden richness of microbial diversity on the planet. The oceanic microbiome plays a significant role in the ecological biogeochemistry of the planet's oceans. The largest scale of ecological organization

10043-404: The interplay among ecological processes that operate and influence patterns at different scales that grade into each other, 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. "What were wholes on one level become parts on

10164-412: The interplay of development and environmental expression of traits. Resident species evolve traits that are fitted to the selection pressures of their local environment. This tends to afford them a competitive advantage and discourages similarly adapted species from having an overlapping geographic range. The competitive exclusion principle states that two species cannot coexist indefinitely by living off

10285-402: The latter focuses on materials and energy fluxes. System behaviors must first be arrayed into different levels of the organization. Behaviors corresponding to higher levels occur at slow rates. Conversely, lower organizational levels exhibit rapid rates. For example, individual tree leaves respond rapidly to momentary changes in light intensity, CO 2 concentration, and the like. The growth of

10406-579: The life of an organism. The following definitions are given by the evolutionary biologist Theodosius Dobzhansky : Adaptation differs from flexibility, acclimatization , and learning, all of which are changes during life which are not inherited. Flexibility deals with the relative capacity of an organism to maintain itself in different habitats: its degree of specialization . Acclimatization describes automatic physiological adjustments during life; learning means alteration in behavioural performance during life. Flexibility stems from phenotypic plasticity ,

10527-424: The lifespan of a single leaf. Each of those aphids, in turn, supports diverse bacterial communities. The nature of connections in ecological communities cannot be explained by knowing the details of each species in isolation, because the emergent pattern is neither revealed nor predicted until the ecosystem is studied as an integrated whole. Some ecological principles, however, do exhibit collective properties where

10648-432: The lower adjacent level (according to ecological pyramids ) nearer the abiotic source." Links in food webs primarily connect feeding relations or trophism among species. Biodiversity within ecosystems can be organized into trophic pyramids, in which the vertical dimension represents feeding relations that become further removed from the base of the food chain up toward top predators, and the horizontal dimension represents

10769-558: The most various kinds and sizes. They form one category of the multitudinous physical systems of the universe, which range from the universe as a whole down to the atom. Tansley (1935) Ecosystems may be habitats within biomes that form an integrated whole and a dynamically responsive system having both physical and biological complexes. Ecosystem ecology is the science of determining the fluxes of materials (e.g. carbon, phosphorus) between different pools (e.g., tree biomass, soil organic material). Ecosystem ecologists attempt to determine

10890-433: The mother's pelvis ) and the size needed for an adult brain (about 1400 cm ), means the brain of a newborn child is quite immature. The most vital things in human life (locomotion, speech) just have to wait while the brain grows and matures. That is the result of the birth compromise. Much of the problem comes from our upright bipedal stance, without which our pelvis could be shaped more suitably for birth. Neanderthals had

11011-456: The nature of the unique physical environments that shapes the biodiversity within each. A more recent addition to ecosystem ecology are technoecosystems , which are affected by or primarily the result of human activity. 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

11132-429: The neck and to carry its weight around. Adaptation and function are two aspects of one problem. Pre-adaptation occurs when a population has characteristics which by chance are suited for a set of conditions not previously experienced. For example, the polyploid cordgrass Spartina townsendii is better adapted than either of its parent species to their own habitat of saline marsh and mud-flats. Among domestic animals,

11253-573: The niche is called the ecotope , which is defined as the full range of environmental and biological variables affecting an entire species. Organisms are subject to environmental pressures, but they also modify their habitats. The regulatory feedback between organisms and their environment can affect conditions from local (e.g., a beaver pond ) to global scales, over time and even after death, such as decaying logs or silica skeleton deposits from marine organisms. The process and concept of ecosystem engineering are related to niche construction , but

11374-531: The number of nitrogen fixers , can lead to disproportionate, perhaps irreversible, changes in the system properties." Biodiversity refers to the variety of life and its processes. It includes the variety of living organisms, the genetic differences among them, the communities and ecosystems in which they occur, and the ecological and evolutionary processes that keep them functioning, yet ever-changing and adapting. Noss & Carpenter (1994) Biodiversity (an abbreviation of "biological diversity") describes

11495-399: The observed data. In these island models, the rate of population change is described by: where N is the total number of individuals in the population, b and d are the per capita rates of birth and death respectively, and r is the per capita rate of population change. Using these modeling techniques, Malthus' population principle of growth was later transformed into a model known as

11616-411: The observed performance of long-term communities at higher altitude is significantly better than the performance of new arrivals, even when the new arrivals have had time to acclimatize. There is a relationship between adaptedness and the concept of fitness used in population genetics . Differences in fitness between genotypes predict the rate of evolution by natural selection. Natural selection changes

11737-406: The organization and structure of entire communities. The loss of a keystone species results in a range of dramatic cascading effects (termed trophic cascades ) that alters trophic dynamics, other food web connections, and can cause the extinction of other species. The term keystone species was coined by Robert Paine in 1969 and is a reference to the keystone architectural feature as the removal of

11858-423: The other hand, eats a range of food, and can survive in many different conditions. Examples are humans, rats, crabs and many carnivores. The tendency to behave in a specialized or exploratory manner is inherited—it is an adaptation. Rather different is developmental flexibility: "An animal or plant is developmentally flexible if when it is raised in or transferred to new conditions, it changes in structure so that it

11979-482: The other species, such as with flowering plants and pollinating insects . In mimicry , species evolve to resemble other species; in mimicry this is a mutually beneficial co-evolution as each of a group of strongly defended species (such as wasps able to sting) come to advertise their defenses in the same way. Features evolved for one purpose may be co-opted for a different one, as when the insulating feathers of dinosaurs were co-opted for bird flight . Adaptation

12100-507: The phenotype as a whole is the target of selection, it is impossible to improve simultaneously all aspects of the phenotype to the same degree. Consider the antlers of the Irish elk , (often supposed to be far too large; in deer antler size has an allometric relationship to body size). Antlers serve positively for defence against predators , and to score victories in the annual rut . But they are costly in terms of resources. Their size during

12221-407: The process of adaptation is never fully complete. Over time, it may happen that the environment changes little, and the species comes to fit its surroundings better and better, resulting in stabilizing selection. On the other hand, it may happen that changes in the environment occur suddenly, and then the species becomes less and less well adapted. The only way for it to climb back up that fitness peak

12342-468: The published work of George Perkins Marsh ("Man and Nature"). Within an ecosystem, organisms are linked to the physical and biological components of their environment to which they are adapted. Ecosystems are complex adaptive systems where the interaction of life processes form self-organizing patterns across different scales of time and space. Ecosystems are broadly categorized as terrestrial , freshwater , atmospheric, or marine . Differences stem from

12463-502: The rate of change in population size ( d N ( t ) / d t {\displaystyle \mathrm {d} N(t)/\mathrm {d} t} ) will grow to approach equilibrium, where ( d N ( t ) / d t = 0 {\displaystyle \mathrm {d} N(t)/\mathrm {d} t=0} ), when the rates of increase and crowding are balanced, r / α {\displaystyle r/\alpha } . A common, analogous model fixes

12584-471: The relative frequencies of alternative phenotypes, insofar as they are heritable . However, a phenotype with high adaptedness may not have high fitness. Dobzhansky mentioned the example of the Californian redwood , which is highly adapted, but a relict species in danger of extinction . Elliott Sober commented that adaptation was a retrospective concept since it implied something about the history of

12705-424: The same limiting resource ; one will always out-compete the other. When similarly adapted species overlap geographically, closer inspection reveals subtle ecological differences in their habitat or dietary requirements. Some models and empirical studies, however, suggest that disturbances can stabilize the co-evolution and shared niche occupancy of similar species inhabiting species-rich communities. The habitat plus

12826-500: The same sex and species, in exclusive relation to reproduction." The kind of sexual selection represented by the peacock is called ' mate choice ,' with an implication that the process selects the more fit over the less fit, and so has survival value. The recognition of sexual selection was for a long time in abeyance, but has been rehabilitated. The conflict between the size of the human foetal brain at birth, (which cannot be larger than about 400 cm , else it will not get through

12947-399: The site will disappear unless rescued by an adjacent source patch or environmental conditions become more favorable. Metapopulation models examine patch dynamics over time to answer potential questions about spatial and demographic ecology. The ecology of metapopulations is a dynamic process of extinction and colonization. Small patches of lower quality (i.e., sinks) are maintained or rescued by

13068-526: The speed and degree of the change. When the habitat changes, three main things may happen to a resident population: habitat tracking, genetic change or extinction. In fact, all three things may occur in sequence. Of these three effects only genetic change brings about adaptation. When a habitat changes, the resident population typically moves to more suitable places; this is the typical response of flying insects or oceanic organisms, which have wide (though not unlimited) opportunity for movement. This common response

13189-524: The study of ecology into a conceptually manageable framework, the biological world is organized into a nested hierarchy , ranging in scale from genes , to cells , to tissues , to organs , to organisms , to species , to populations , to guilds , to communities , to ecosystems , to biomes , and up to the level of the biosphere . This framework forms a panarchy and exhibits non-linear behaviors; this means that "effect and cause are disproportionate, so that small changes to critical variables, such as

13310-432: The sum of the components explain the properties of the whole, such as birth rates of a population being equal to the sum of individual births over a designated time frame. The main subdisciplines of ecology, population (or community ) ecology and ecosystem ecology , exhibit a difference not only in scale but also in two contrasting paradigms in the field. The former focuses on organisms' distribution and abundance, while

13431-569: The target of the poison, the sodium pump , resulting in target site insensitivity. These same adaptive mutations and similar changes at the same amino acid sites were found to evolve in a parallel manner in distantly related insects that feed on the same plants, and even in a bird that feeds on monarchs through convergent evolution , a hallmark of adaptation. Convergence at the gene-level across distantly related species can arise because of evolutionary constraint. Habitats and biota do frequently change over time and space. Therefore, it follows that

13552-535: The time of the ancient Greek philosophers such as Empedocles and Aristotle . In 18th and 19th century natural theology , adaptation was taken as evidence for the existence of a deity. Charles Darwin and Alfred Russel Wallace proposed instead that it was explained by natural selection. Adaptation is related to biological fitness , which governs the rate of evolution as measured by change in allele frequencies . Often, two or more species co-adapt and co-evolve as they develop adaptations that interlock with those of

13673-458: The total biology of the species. Adaptation is primarily a process rather than a physical form or part of a body. An internal parasite (such as a liver fluke ) can illustrate the distinction: such a parasite may have a very simple bodily structure, but nevertheless the organism is highly adapted to its specific environment. From this we see that adaptation is not just a matter of visible traits: in such parasites critical adaptations take place in

13794-468: The traditional sources of material on which natural selection could act. In addition, horizontal gene transfer is possible between organisms in different species, using mechanisms as varied as gene cassettes , plasmids , transposons and viruses such as bacteriophages . In coevolution , where the existence of one species is tightly bound up with the life of another species, new or 'improved' adaptations which occur in one species are often followed by

13915-670: The tree responds more slowly and integrates these short-term changes. O'Neill et al. (1986) The scale of ecological dynamics can operate like a closed system, such as aphids migrating on a single tree, while at the same time remaining open about broader scale influences, such as atmosphere or climate. Hence, ecologists classify ecosystems hierarchically by analyzing data collected from finer scale units, such as vegetation associations , climate, and soil types , and integrate this information to identify emergent patterns of uniform organization and processes that operate on local to regional, landscape , and chronological scales. To structure

14036-415: The underlying causes of these fluxes. Research in ecosystem ecology might measure primary production (g C/m^2) in a wetland in relation to decomposition and consumption rates (g C/m^2/y). This requires an understanding of the community connections between plants (i.e., primary producers) and the decomposers (e.g., fungi and bacteria). The underlying concept of an ecosystem can be traced back to 1864 in

14157-603: The upper and lower jaws and the hyoid bone of their synapsid ancestors, and further back still were part of the gill arches of early fish. The word exaptation was coined to cover these common evolutionary shifts in function. The flight feathers of birds evolved from the much earlier feathers of dinosaurs , which might have been used for insulation or for display. Animals including earthworms , beavers and humans use some of their adaptations to modify their surroundings, so as to maximize their chances of surviving and reproducing. Beavers create dams and lodges, changing

14278-439: The use of a location by the animal." For example, a habitat might be an aquatic or terrestrial environment that can be further categorized as a montane or alpine ecosystem. Habitat shifts provide important evidence of competition in nature where one population changes relative to the habitats that most other individuals of the species occupy. For example, one population of a species of tropical lizard ( Tropidurus hispidus ) has

14399-593: Was coined in 1866 by the German scientist Ernst Haeckel . The science of ecology as we know it today began with a group of American botanists in the 1890s. Evolutionary concepts relating to adaptation and natural selection are cornerstones of modern ecological theory . Ecosystems are dynamically interacting systems of organisms, the communities they make up, and the non-living ( abiotic ) components of their environment. Ecosystem processes, such as primary production , nutrient cycling , and niche construction , regulate

14520-965: Was first founded by students at Prescott College who articulated the original vision in 1996 and convened colleges under the consortium as the North American Alliance for Green Education (NAAGE), and later rebranded as “the Eco-8” and then "the Eco League". These institutions included Northland College in Ashland, Wisconsin ; Prescott College in Prescott, Arizona ; College of the Atlantic in Bar Harbor, Maine ; and Dickinson College in Carlisle, Pennsylvania , all current members of

14641-414: Was seen as a fixed relationship between an organism and its habitat. It was not appreciated that as the climate changed, so did the habitat; and as the habitat changed, so did the biota . Also, habitats are subject to changes in their biota: for example, invasions of species from other areas. The relative numbers of species in a given habitat are always changing. Change is the rule, though much depends on

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