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  Natural, physical, or material world and its phenomena, or Natural environment  All living and non-living things occurring naturally, generally on Earth
  • Ecosystem  Community of living organisms together with the nonliving components of their environment, or Biome  Community of organisms associated with an environment
    • Community (ecology)  Associated populations of species in a given area, or Biocoenosis  The interacting organisms living together in a habitat in the field of palaeontology
      • Species  Basic unit of taxonomic classification, below genus
        • Population  All the organisms of a given species that live in the specified region
          • Organism  Any individual living physical system
  • 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:

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  The 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  Study of the dynamics of species populations and how these populations interact with the environment
  • Community ecology, also known as synecology  Associated populations of species in a given area
  • Ecosystem ecology  The study of living and non-living components of ecosystems and their interactions
  • Systems ecology  Holistic approach to the study of ecological systems
  • Landscape ecology  The 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 the distribution of species and ecosystems in geographic space and through geological time
  • Insect ecology  The study of how insects interact with the surrounding environment
  • Microbial ecology  Study of the relationship of microorganisms with their environment
  • Paleoecology  The 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  The study of the interaction of sea-floor organisms with each other and with the environment
  • Desert ecology  The study of interactions between both biotic and abiotic components of desert environments
  • Forest ecology  The study of interactions between the biota and environment in forets
  • 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  The study of the relation of living organisms with each other and their surroundings in the context of an urban environment.

By geographic or climatic area under study

  • Arctic ecology  The study of the relationships between biotic and abiotic factors in the arctic
  • Polar ecology  The relationship between plants and animals and a polar environment
  • Tropical ecology  The study of the relationships between the biotic and abiotic components of the tropics

By spatial scale under study

  • Global ecology
  • Landscape ecology  The science of relationships between ecological processes in the environment and particular ecosystems
  • Landscape limnology  The spatially explicit study of lakes, streams, and wetlands as they interact with freshwater, terrestrial, and human landscapes to determine the effects of pattern on ecosystem processes across temporal and spatial scales
  • Spatial ecology  Study of the distribution or space occupied by species
  • Macroecology  The 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  A field of evolutionary biology that applies molecular population genetics, molecular phylogenetics, and genomics to traditional ecological questions

By ecological aspects or phenomena under investigation

  • Chemical ecology 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  The study of adaptation of an organism's physiology to environmental conditions which studies the interaction of physiological traits with the abiotic environment;
  • Ecotoxicology 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 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 the ecology of the pedosphere;

By technique used for investigation

By environmental approach

  • Applied ecology 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  Special consideration to individuals solely on the basis of their species membership involves the assignment of different values, rights, or special consideration to individuals solely on the basis of their species membership.
  • Technocentrism value system that is centered on technology and its ability to control and protect the environment.

Ecology-involved interdisciplinary fields

Other subdisciplines

Other branches of ecology include:

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

Biogeographic regions

Map of six of the world's eight terrestrial realms
  Oceania and Antarctic realms not shown
  • Biosphere  The 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):


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 ecology  Aspect of history covering the study of ecology

General ecology concepts

  • Ecological succession  The process of change in the species structure of an ecological community over time
  • Carrying capacity  The maximum population size of the species that the environment can support indefinitely
    • Ecological collapse  Situation in which an ecosystem suffers a drastic, possibly permanent, reduction in carrying capacity for all organisms
  • Competitive exclusion principle  Proposition that two species competing for the same limiting resource cannot coexist at constant population values
  • Ecological yield  Harvestable population growth in an ecosystem
  • Autotroph  Any organism that produces complex organic compounds from simple substances present in its surroundings
  • Bacteria  Domain of micro-organisms
  • Bioinvader  Organism occurring in a new habitat
  • Biomass  Biological material used as a renewable energy source
  • Biotic material  Any material that originates from living organisms
  • Carbon cycle  Biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere
  • Climate  Statistics of weather conditions in a given region over long periods
  • Ecological selection  Natural selection without sexual selection
  • Gaia hypothesis  Paradigm that living organisms interact with their surroundings in a self-regulating system
  • Natural resource  Resources that exist without actions of humankind
  • Monoculture  The agricultural practice of producing a single crop at a time
  • Decomposition  The process in which organic substances are broken down into simpler organic matter
  • Inorganic substance  A substance lacking organic constituents
  • Ecological crisis  Change to the environment that destabilizes the continued survival of a population
  • Ecological extinction  Reduction of a species' abundance to the point that, though still present, it stops interacting with other species
  • Ecophagy  The literal consumption of an ecosystem
  • Ecological niche  The 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  Any process in which an organism has an effect on another organism
    • Neutralism  A relationship between two species that interact but do not affect each other
    • Amensalism  Asymmetric interaction between species
    • Ecological facilitation  Species interactions that benefit at least one of the participants and cause harm to neither
      • Mutualism  Relationship between organisms of different species in which each individual benefits from the activity of the other
      • 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 where a predator kils and eats a prey organism
    • Parasitism  relationship between species where one organism lives on or in another organism, causing it harm

See also