Outline of ecology

The following outline is provided as an overview of and topical guide to ecology:

Ecology – scientific study of the distribution and abundance of living organisms and how the distribution and abundance are affected by interactions between the organisms and their environment. The environment of an organism includes both physical properties, which can be described as the sum of local abiotic factors such as solar insolation, climate and geology, as well as the other organisms that share its habitat. Also called ecological science.

Essence of ecology

Nature – Material world and its phenomena, or Natural environment – Living and non-living things on Earth
Ecosystem – Community of living organisms together with the nonliving components of their environment, or Biome – Biogeographical unit with a particular biological community
- Community (ecology) – Associated populations of species in a given area, or Biocoenosis – Interacting organisms living together in a habitat
  - Species – Basic unit of taxonomic classification, below genus
    - Population – All the organisms of a given species that live in a specified region
      - Organism – Individual living life form
Biodiversity – Variety and variability of life forms
- Food web – Natural interconnection of food chains

Other criteria

Ecology can also be classified on the basis of:

the primary kinds of organism under study, e.g. animal ecology, plant ecology, insect ecology;
the biomes principally studied, e.g. forest ecology, grassland ecology, desert ecology, benthic ecology, marine ecology, urban ecology;
the geographic or climatic area, e.g. arctic ecology, tropical ecology
the spatial scale under consideration, e.g. macroecology, landscape ecology;
the philosophical approach, e.g. systems ecology which adopts a holistic approach;
the methods used, e.g. molecular ecology.

Subdisciplines of ecology, and subdiscipline classification

Ecology is a broad discipline comprising many subdisciplines. The field of ecology can be subdivided according to several classification schemes:

By level of complexity or scope

Arranged from lowest to highest complexity:

Ecophysiology – Study of adaptation of an organism's physiology to environmental conditions, or Behavioral ecology – Study of the evolutionary basis for animal behavior due to ecological pressures
Population ecology, also known as autoecology – Sub-field of ecology
Community ecology, also known as synecology – Associated populations of species in a given area
Ecosystem ecology – Study of living and non-living components of ecosystems and their interactions
Systems ecology – Holistic approach to the study of ecological systems
Landscape ecology – Science of relationships between ecological processes in the environment and particular ecosystems

By organisms under study

Animal ecology – Scientific study of the relationships between living animals and their environment
Behavioral ecology – Study of the evolutionary basis for animal behavior due to ecological pressures
Biogeography – Study of distribution of species
Insect ecology – The study of how insects interact with the surrounding environment
Microbial ecology – Study of the relationship of microorganisms with their environment
Paleoecology – Study of interactions between organisms and their environments across geologic timescales
Plant ecology – The study of effect of the environment on the abundance and distribution of plants

By biome under study

Benthic ecology – Ecological region at the lowest level of a body of water
Desert ecology – The study of interactions between both biotic and abiotic components of desert environments
Forest ecology – Study of interactions between the biota and environment in forests.
Grassland ecology
Marine ecology – The study of the interactions between organisms and environment in the sea
Aquatic ecology – The study of interactions between organisms and the environment in water
Urban ecology – Scientific study of living organisms

By geographic or climatic area under study

Arctic ecology – Study of the relationships between biotic and abiotic factors in the arctic
Polar ecology – Relationship between plants and animals and a polar environment
Tropical ecology – Study of the relationships between the biotic and abiotic components of the tropics

By spatial scale under study

Global ecology
Landscape ecology – Science of relationships between ecological processes in the environment and particular ecosystems
Landscape limnology – Spatially explicit study of lakes, streams, and wetlands as they interact with landscapes
Spatial ecology – Study of the distribution or space occupied by species
Macroecology – Study of relationships between organisms and their environment at large spatial scales
Microecology – Microbial ecology or ecology of a microhabitat
Microbial ecology – Study of the relationship of microorganisms with their environment
Molecular ecology – Subdiscipline of ecology

By ecological aspects or phenomena under investigation

Chemical ecology – Study of chemically-mediated interactions between living organisms – which deals with the ecological role of biological chemicals used in a wide range of areas including defense against predators and attraction of mates;
Ecophysiology – Study of adaptation of an organism's physiology to environmental conditions – which studies the interaction of physiological traits with the abiotic environment;
Ecotoxicology – study of effects of released pollutants on the environment and biota – which looks at the ecological role of toxic chemicals (often pollutants, but also naturally occurring compounds);
Evolutionary ecology – Interaction of biology and evolution – or ecoevolution which looks at evolutionary changes in the context of the populations and communities in which the organisms exist;
Fire ecology – Study of fire in ecosystems – which looks at the role of fire in the environment of plants and animals and its effect on ecological communities;
Functional ecology – branch of ecology – the study of the roles, or functions, that certain species (or groups thereof) play in an ecosystem;
Genetic ecology – Study of genetic material in the environment
Soil ecology – Study of the interaction of soil and life – the ecology of the pedosphere;

By technique used for investigation

Field ecology
Quantitative ecology – application of advanced mathematical and statistical tools to perform ecological research
Theoretical ecology – Scientific discipline – the development of ecological theory, usually with mathematical, statistical and/or computer modeling tools;

By environmental approach

Applied ecology – sub-field within ecology that considers the application of the science of ecology to real-world (usually management) questions – the practice of employing ecological principles and understanding to solve real world problems (includes agroecology and conservation biology);
Conservation ecology – Study of threats to biological diversity – which studies how to reduce the risk of species extinction;
Deep ecology – Ecological and environmental philosophy – an ecological and environmental philosophy promoting the inherent worth of living beings regardless of their instrumental utility to human needs, plus a radical restructuring of modern human societies in accordance with such ideas.
Ecosophy – Philosophy of ecological harmony or equilibrium as developed by Arne Næss or Félix Guattari – philosophy of ecological harmony or equilibrium.
Restoration ecology – Scientific study of renewing and restoring ecosystems – which attempts to understand the ecological basis needed to restore impaired or damaged ecosystems.
Speciesism – Philosophical term on species treatment – involves the assignment of different values, rights, or special consideration to individuals solely on the basis of their species membership.
Technocentrism – Value system centered on technology and its ability to control and protect the environment – value system that is centered on technology and its ability to control and protect the environment.

Ecology-involved interdisciplinary fields

Agroecology – Study of ecological processes in agriculture
Biogeochemistry – Study of chemical cycles of the earth that are either driven by or influence biological activity
Ecological design – Design approach sensitive to environmental impacts
Ecological economics – Interdependence of human economies and natural ecosystems
Ecological engineering – Environmental engineering
Festive ecology – Study of ecology and cultural events
Human ecology – Study of the relationship between humans and their natural, social, and built environments
Ecological anthropology – Study of cultural adaptations to environments
Social ecology – Study of relationships between people and their environment
Ecological health – term in medicine about management of environmental factors that may reduce the risk of unhealthy behavior
Environmental psychology – Academic study of the mind's relationship to one's immediate surroundings
Industrial ecology – Study of matter and energy flow in industrial systems
Paleoecology – Study of interactions between organisms and their environments across geologic timescales

Other subdisciplines

Other branches of ecology include:

ecological succession, which focuses on understanding directed vegetation change;
thermal ecology, the study of the relationship between temperature and organisms;

Ecology has also inspired (and lent its name to) other non-biological disciplines such as

Biogeographic regions

Biosphere – Global sum of all ecosystems on Earth

Terrestrial realms

Biogeographic realm – Broadest biogeographic division of Earth's land surface The World Wildlife Fund (WWF) developed a system of eight biogeographic realms (ecozones):

Nearctic – Biogeographic realm encompassing temperate North America 22.9 mil. km² (including most of North America)
Palearctic – Biogeographic realm covering most of Eurasia 54.1 mil. km² (including the bulk of Eurasia and North Africa)
Afrotropical – One of Earth's eight biogeographic realms 22.1 mil. km² (including Sub-Saharan Africa)
Indomalayan – One of the Earth's eight ecozones 7.5 mil. km² (including the South Asian subcontinent and Southeast Asia)
Australasian – One of the Earth's eight biogeographic realms 7.7 mil. km² (including Australia, New Guinea, and neighbouring islands). The northern boundary of this zone is known as the Wallace line.
Neotropical – One of Earth's eight biogeographic realms 19.0 mil. km² (including South America and the Caribbean)
Oceanian – Terrestrial biogeographic realm 1.0 mil. km² (including Polynesia, Fiji and Micronesia)
Antarctic – One of Earth's eight biogeographic realms 0.3 mil. km² (including Antarctica).

Ecoregions

Ecoregion – Ecologically and geographically defined area that is smaller than a bioregion

The World has over 800 terrestrial ecoregions. See Lists of ecoregions by country.

History of ecology

History of human ecology

General ecology concepts

Ecological succession – Process of change in the species structure of an ecological community over time
- Primary succession – Gradual growth and change of an ecosystem on new substrate
  - Pioneer species – First species to colonize or inhabit damaged ecosystems
  - Ruderal species – Plant species that is first to colonize disturbed lands
  - Supertramp – Any type of animal which follows the strategy of high dispersion among many different habitats
- Secondary succession – Redevelopment of an encology after an event that changes it radically
Carrying capacity – Maximum population size of a species that an environment can support
- Ecological collapse – Ecological communities abruptly losing biodiversity, often irreversibly
Competitive exclusion principle – Ecology proposition
Ecological yield – Harvestable population growth in an ecosystem
Autotroph – Organism type
Bacteria – Domain of microorganisms
Bioinvader – Organism occurring in a new habitat
Biomass – Biological material from either living (see ecology) or recently living organisms (see bioenergy)
Biotic material – Any material originating from living organisms
Carbon cycle – Natural processes of carbon exchange
Climate – Long-term weather pattern of a region
Ecological selection – Mechanism of evolution by differential survival and reproduction of individuals
Gaia hypothesis – Scientific hypothesis about Earth
Natural resource – Resources that exist without actions of humankind.
Monoculture – Farms producing only one crop at a time
Decomposition – Process in which organic substances are broken down into simpler organic matter
- Organic matter – Matter composed of organic compounds
Inorganic substance – A substance lacking organic constituents
- Detritus – Dead particulate organic material
- Biodegradation – Decomposition by living organisms
Ecological crisis – Change to the environment that destabilizes the continued survival of a population
Ecological extinction – Ecology term
Ecophagy – The literal consumption of an ecosystem
Ecological niche – Fit of a species living under specific environmental conditions
Niche differentiation - the process by which competing species use the environment differently in a way that helps them to coexist.
Biological interaction – Effect that organisms have on other organisms
- Neutralism – A relationship between two species that interact but do not affect each other
- Amensalism – Close, long-term biological interaction between distinct organisms (usually species)
- Ecological facilitation – Species interactions that benefit at least one of the participants and cause harm to neither
  - Mutualism – Mutually beneficial interaction between species
  - Commensalism – Beneficial symbiosis between species
- Coexistence theory - a framework to understand and explain how ecologically similar species can coexist without competitively excluding each other
- Competition – Interaction where the fitness of one organism is lowered by the presence of another organism
- Predation – Biological interaction
- Parasitism – Relationship between species where one organism lives on or in another organism, causing it harm