Biome with enough average annual precipitation (at least 76 centimeters, or 30 inches) to support growth of various tree species and smaller forms of vegetation. Compare desert, grassland.
Biome found in regions where moderate annual average precipitation (25-76 centimeters, or 10-]30 inches) is enough to support the growth of grass and small plants but not enough to support large stands of trees. Compare desert, forest.
Distance from the equator. Compare altitude.
Periods of heavy rains experienced on continents lying north or south of warm oceans.
Perennially frozen layer of the soil that forms when the water there freezes. It is found in arctic tundra.
Plants, such as desert cacti, that survive in dry climates by having no leaves, thus reducing the loss of scarce water. They store water and use sunlight to produce the food they need in the thick, fleshy tissue of their green stems and branches. Compare deciduous plants, evergreen plants.
Long, thin, low offshore islands of sediment that generally run parallel to the shore along some coasts.
Land along a coastline, extending inland from an estuary, that is covered with salt water all or part of the year. Examples are marshes, bays, lagoons, tidal flats, and mangrove swamps.
Compare inland wetland.
Overnourishment of aquatic ecosystems with plant nutrients (mostly nitrates and phosphates) because of human activities such as agriculture, urbanization, and discharges from industrial plants and sewage treatment plants. See eutrophication.
Partially enclosed coastal area at the mouth of a river where its fresh water, carrying fertile silt and runoff from the land, mixes with salty seawater.
Upper layer of a body of water through which sunlight can penetrate and support photosynthesis.
Lake with a large or excessive supply of plant nutrients, mostly nitrates and phosphates. Compare mesotrophic lake, oligotrophic lake.
Land away from the coast, such as a swamp, marsh, or bog, that is covered all or part of the time with fresh water. Compare coastal wetland.
Swamps found on the coastlines in warm tropical climates. They are dominated by mangrove trees, any of about 55 species of trees and shrubs that can live partly submerged in the salty environment of coastal swamps.
Lake with a low supply of plant nutrients.
Compare eutrophic lake, mesotrophic lake.
Small, drifting plants, mostly algae and bacteria, found in aquatic ecosystems. Compare plankton, zooplankton.
Fresh water from precipitation and melting ice that flows on the earth’s surface into nearby streams, lakes, wetlands, and reservoirs. See reliable runoff, surface runoff, surface water. Compare groundwater.
Movement of nutrient-rich bottom water to the ocean’s surface. This can occur far from shore but usually occurs along certain steep coastal areas where the surface layer of ocean water is pushed away from shore and replaced by cold, nutrient-rich bottom water.
Land area that delivers water, sediment, and dissolved substances via small streams to a major stream (river).
Land that is covered all or part of the time with salt water or fresh water, excluding streams, lakes, and the open ocean.
See coastal wetland, inland wetland.
Animal plankton. Small floating herbivores that feed on plant plankton (phytoplankton). Compare phytoplankton.
Plant that grows, sets seed, and dies in one growing season. Compare perennial.
Fairly stable, self-sustaining community in an advanced stage of ecological succession; usually has a diverse array of species and ecological niches; captures and uses energy and cycles critical chemicals more efficiently than simpler, immature communities.
Compare immature community.
An interaction between organisms of different species in which one type of organism benefits and the other type is neither helped nor harmed to any great degree. Compare mutualism.
Two or more individual organisms of a single species (intraspecific competition) or two or more individuals of different species (interspecific competition) attempting to use the same scarce resources in the same ecosystem.
A discrete event that disrupts an ecosystem or community. Examples of natural disturbances include fires, hurricanes, tornadoes, droughts, and floods. Examples of human-caused disturbances include deforestation, overgrazing, and plowing.
Process in which communities of plant and animal species in a particular area are replaced over time by a series of different and often more complex communities.
See primary succession, secondary succession.
Natural services or natural capital that support life on the earth and are essential to the quality of human life and the functioning of the world’s economies. See natural resources.
Breakup of a habitat into smaller pieces, usually as a result of human activities.
Species that serve as early warnings that a community or ecosystem is being degraded. Compare keystone species, native species, nonnative species.
See nonnative species.
Species that play roles affecting many other organisms in an ecosystem. Compare indicator species, native species, nonnative species.
Type of species interaction in which both participating species generally benefit.
Species that normally live and thrive in a particular ecosystem. Compare indicator species, keystone species, nonnative species.
Species that migrate into an ecosystem or are deliberately or accidentally introduced into an ecosystem by humans. Compare native species.
Interaction between species in which one organism, called the parasite, preys on another organism, called the host, by living on or in the host. See host, parasite.
Plant that can live for more than 2 years. Compare annual.
First hardy species, often microbes, mosses, and lichens, that begin colonizing a site as the first stage of ecological succession. See ecological succession, pioneer community.
Situation in which an organism of one species (the predator) captures and feeds on parts or all of an organism of another species (the prey).
Ecological succession in a bare area that has never been occupied by a community of organisms.
See ecological succession. Compare secondary succession.
Ability of a living system to restore itself to original condition after being exposed to an outside disturbance that is not too drastic. See constancy, inertia.
Ecological succession in an area in which natural vegetation has been removed or destroyed but the soil is not destroyed. See ecological succession. Compare primary succession.
theory of island biogeography
The number of species found on an island is determined by a balance between two factors: the immigration rate (of species new to the island) from other inhabited areas and the extinction rate (of species established on the island). The model predicts that at some point the rates of immigration and extinction will reach an equilibrium point that determines the island’s average number of different species (species diversity).