Ecology

Levels, scope, and scale of organization

The scope of ecology contains a wide profile of interacting levels of organization spanning micro-level 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. Ecosystems are dynamic, they do non always follow a linear successional path, but they are always changing, sometimes rapidly and sometimes so slowly that it can take thousands of years for ecological processes to bring about certain successional stages of a forest. An ecosystem's area can reconstruct greatly, from tiny to vast. A single tree is of little consequence to the shape of a forest ecosystem, but critically relevant to organisms living in and on it. Several generations of an aphid population can cost over the lifespan of a single leaf. each of those aphids, in turn, support diverse bacterial communities. The classification of connections in ecological communities cannot be explained by knowing the details of used to refer to every one of two or more people or matters 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 the or situation. of the components explain the properties of the whole, such(a) as birth rates of a population being live to the total of individual births over a designated time frame.

The leading subdisciplines of ecology, population or community ecology and ecosystem ecology, exhibit a difference not only of scale but also of two contrasting paradigms in the field. The former focuses on organisms' distribution and abundance, while the latter focuses on materials and energy to direct or establishment fluxes.

System behaviors must first be arrayed into different levels of organization. Behaviors corresponding to higher levels occur at gradual rates. Conversely, lower organizational levels exhibit rapid rates. For example, individual tree leavesrapidly to momentary reorganize in light intensity, CO₂ concentration, and the like. The growth of the tree responds more slowly and integrates these short-term changes.

O'Neill et al. 1986: 76 

The scale of ecological dynamics can operate like a closed system, such as aphids migrating on a single tree, while at the same time extend open with regard to broader scale influences, such(a) as atmosphere or climate. Hence, ecologists categorize 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 company and processes that operate on local to regional, landscape, and chronological scales.

To profile 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 communities, to ecosystems, to biomes, and up to the level of the biosphere. This return example 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 the number of nitrogen fixers, can lead to disproportionate, perhaps irreversible, changes in the system properties.": 14 

Biodiversity referenced 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: 5 

Biodiversity an abbreviation of "biological diversity" describes the diversity of life from genes to ecosystems and spans every level of biological organization. The term has several interpretations, and there are numerous 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 sustains and upgrading human quality of life. Conservation priorities and supervision techniques require different approaches and considerations to consultation 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 predominance has been implicated as one mechanism by which those utility losses are experienced. An understanding of biodiversity has practical application for species and ecosystem-level conservation planners as they make administration recommendations to consulting firms, governments, and industry.

The habitat of a species describes the environment over which a species is asked to arise 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 business dimensions, each representing a biotic or abiotic environmental variable; that is, any element or characteristic of the environment related directly e.g. forage biomass and quality or indirectly e.g. elevation to the use of a location by the animal.": 745  For example, a habitat might be an aquatic or terrestrial environment that can be further categorized as a montane or alpine ecosystem. Habitat shifts give important evidence of competition in nature where one population changes relative to the habitats that almost other individuals of the species occupy. For example, one population of a species of tropical lizard Tropidurus hispidus has a flattened body relative to the leading populations that live in open savanna. The population that lives in an isolated rock outcrop hides in crevasses where its flattened body enable 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 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 Euclidean hyperspace whose dimensions are defined as environmental variables and whose size is a function of the number of values that the environmental values may assume for which an organism has positive fitness.": 71 

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 the interplay of developing 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 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,that disturbances can stabilize the co-evolution and shared up niche occupancy of similar species inhabiting species-rich communities. The habitat plus the niche is called the ecotope, which is defined as the full range of environmental and biological variables affecting an entire species.

Organisms are intended to environmental pressures, but they also change 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 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.": 373 

The ecosystem engineering concept has stimulated 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 technology occurs in the nests of social insects, including ants, bees, wasps, and termites. There 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 the tangible substance that goes into the makeup of a physical object and a legacy niche that was constructed previously their time.

Biomes are larger units of organization that classify 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 add 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 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 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 CO₂ and O₂ composition has been affected by the biogenic flux of gases coming from respiration and photosynthesis, with levels fluctuating over time in explanation to the ecology and evolution of plants and animals. Ecological view 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 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 models normally start with four variables: death, birth, immigration, and emigration.

An example of an introductory population framework 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 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 requested as the logistic equation by Pierre Verhulst:

where Nt is the number of individuals measured as biomass density as a function of time, t, r is the maximum per-capita rate of change ordinarily known as the intrinsic rate of growth, and is the crowding coefficient, which represents the reduction in population growth rate per individual added. The formula states that the rate of change in population size will grow to approach equilibrium, where , when the rates of put and crowding are balanced, . A common, analogous model fixes the equilibrium, 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 analysed using mathematical techniques such as matrix algebra. The information is used for managing wildlife stocks and setting harvest quotas. In cases where basic models are insufficient, ecologists may undertake different kinds of statistical methods, such as the Akaike information criterion, or ownership 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".: 105  Metapopulation ecology 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 except other kinds of movement because it involves the seasonal departure and return of individuals from a habitat. Migration is also a population-level phenomenon, as with the migration outes 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 advanced climates. These migration routes involved an expansion of the range as plant populations expanded from one area to another. There is a larger taxonomy of movement, such as commuting, foraging, territorial behaviour, 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.