Population ecology

Biodiversity of a coral reef. Corals adapt to and modify their environment by forming calcium carbonate skeletons. This provides growing conditions for future generations and forms a habitat for many other species.

Jellyfish population trends by LME.jpg

- Population ecology

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Conservation biology

Study of the conservation of nature and of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions.

2016 conservation indicator which includes the following indicators: marine protected areas, terrestrial biome protection (global and national), and species protection (global and national).
Efforts are made to preserve the natural characteristics of Hopetoun Falls, Australia, without affecting visitors' access.
White gyrfalcons drawn by John James Audubon
More conservation research is needed for understanding ecology and behaviour of asiatic wild dog in central China.
Roosevelt and Muir on Glacier Point in Yosemite National Park
A pie chart image showing the relative biomass representation in a rain forest through a summary of children's perceptions from drawings and artwork (left), through a scientific estimate of actual biomass (middle), and by a measure of biodiversity (right). Notice that the biomass of social insects (middle) far outweighs the number of species (right).
Tadrart Acacus desert in western Libya, part of the Sahara
An art scape image showing the relative importance of animals in a rain forest through a summary of (a) child's perception compared with (b) a scientific estimate of the importance. The size of the animal represents its importance. The child's mental image places importance on big cats, birds, butterflies, and then reptiles versus the actual dominance of social insects (such as ants).

Conservation biology is tied closely to ecology in researching the population ecology (dispersal, migration, demographics, effective population size, inbreeding depression, and minimum population viability) of rare or endangered species.

Population dynamics

Type of mathematics used to model and study the size and age composition of populations as dynamical systems.

Operophtera brumata populations are geometric.

The concept is commonly used in insect population ecology or management to determine how environmental factors affect the rate at which pest populations increase.

Ecology

Study of the relationships between living organisms, including humans, and their physical environment.

Biodiversity of a coral reef. Corals adapt to and modify their environment by forming calcium carbonate skeletons. This provides growing conditions for future generations and forms a habitat for many other species.
Long-tailed broadbill building its nest
Termite mounds with varied heights of chimneys regulate gas exchange, temperature and other environmental parameters that are needed to sustain the internal physiology of the entire colony.
Interspecific interactions such as predation are a key aspect of community ecology.
A riparian forest in the White Mountains, New Hampshire (USA) is an example of ecosystem ecology
Generalized food web of waterbirds from Chesapeake Bay
A trophic pyramid (a) and a food-web (b) illustrating ecological relationships among creatures that are typical of a northern boreal terrestrial ecosystem. The trophic pyramid roughly represents the biomass (usually measured as total dry-weight) at each level. Plants generally have the greatest biomass. Names of trophic categories are shown to the right of the pyramid. Some ecosystems, such as many wetlands, do not organize as a strict pyramid, because aquatic plants are not as productive as long-lived terrestrial plants such as trees. Ecological trophic pyramids are typically one of three kinds: 1) pyramid of numbers, 2) pyramid of biomass, or 3) pyramid of energy.
Sea otters, an example of a keystone species
Social display and colour variation in differently adapted species of chameleons (Bradypodion spp.). Chameleons change their skin colour to match their background as a behavioural defence mechanism and also use colour to communicate with other members of their species, such as dominant (left) versus submissive (right) patterns shown in the three species (A-C) above.
Mutualism: Leafhoppers (Eurymela fenestrata) are protected by ants (Iridomyrmex purpureus) in a mutualistic relationship. The ants protect the leafhoppers from predators and stimulate feeding in the leafhoppers, and in return, the leafhoppers feeding on plants exude honeydew from their anus that provides energy and nutrients to tending ants.
Bumblebees and the flowers they pollinate have coevolved so that both have become dependent on each other for survival.
Parasitism: A harvestman arachnid being parasitized by mites. The harvestman is being consumed, while the mites benefit from traveling on and feeding off of their host.
The leaf is the primary site of photosynthesis in most plants.
The architecture of the inflorescence in grasses is subject to the physical pressures of wind and shaped by the forces of natural selection facilitating wind-pollination (anemophily).
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The layout of the first ecological experiment, carried out in a grass garden at Woburn Abbey in 1816, was noted by Charles Darwin in The Origin of Species. The experiment studied the performance of different mixtures of species planted in different kinds of soils.

The main 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.

Community (ecology)

A bear with a salmon. Interspecific interactions such as predation are a key aspect of community ecology.
a) A trophic pyramid showing the different trophic levels in a community. b) A food web of the same community
A simple trophic cascade diagram. On the right shows when wolves are absent, showing an increase in elks and reduction in vegetation growth. The left one shows when wolves are present and controlling the elk population.
Table visualising size-symmetric competition, using fish as consumers and crabs as resources.
A generalised graph of a predator-prey population density cycle

In ecology, a community is a group or association of populations of two or more different species occupying the same geographical area at the same time, also known as a biocoenosis, biotic community, biological community, ecological community, or life assemblage.

Habitat

See also Microhabitat (film) or Habitat (disambiguation).

This coral reef in the Phoenix Islands Protected Area provides habitat for numerous marine species.
Few creatures make the ice shelves of Antarctica their habitat, but water beneath the ice can provide habitat for multiple species.
Ibex in an alpine habitat
Rich rainforest habitat in Dominica
Wetland habitat types in Borneo
Desert scene in Egypt
An Antarctic rock split apart to show endolithic lifeforms showing as a green layer a few millimeters thick
Dense mass of white crabs at a hydrothermal vent, with stalked barnacles on right
Twenty five years after the devastating eruption at Mount St. Helens, United States, pioneer species have moved in.

A marine example is when sea urchin populations "explode" in coastal waters and destroy all the macroalgae present.

Maximum sustainable yield

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In population ecology and economics, maximum sustainable yield (MSY) is theoretically, the largest yield (or catch) that can be taken from a species' stock over an indefinite period.

Malthusian growth model

Essentially exponential growth based on the idea of the function being proportional to the speed to which the function grows.

The graph illustrates how exponential growth (green) surpasses both linear (red) and cubic (blue) growth.

It is widely regarded in the field of population ecology as the first principle of population dynamics, with Malthus as the founder.

Spatial ecology

Spatial ecology studies the ultimate distributional or spatial unit occupied by a species.

All adult Eurasian blue tits share the same coloration, unmistakably identifying the morphospecies.

Analysis of spatial trends has been used to research wildlife management, fire ecology, population ecology, disease ecology, invasive species, marine ecology, and carbon sequestration modeling using the spatial relationships and patterns to determine ecological processes and their effects on the environment.

Chris Perrins

Emeritus Fellow of the Edward Grey Institute of Field Ornithology at the University of Oxford, Emeritus Fellow at Wolfson College, Oxford and Her Majesty's Warden of the Swans since 1993.

Edward Grey, 1st Viscount Grey of Fallodon, after whom the Edward Grey Institute is named.

He is renowned for his work on avian population ecology and, in particular, reproductive rates.

Evolutionary economics

Part of mainstream economics as well as a heterodox school of economic thought that is inspired by evolutionary biology.

Heterodox economics family tree.

Their approach can be compared and contrasted with the population ecology or organizational ecology approach in sociology: see Douma & Schreuder (2013, chapter 11).