Unit 8

climate

climate

The long-term prevailing weather conditions at a given place.

abiotic

Nonliving; referring to the physical and chemical properties of an environment.

biotic

Pertaining to the living factors—the organisms—in an environment.

biomes

Any of the world's major ecosystem types, often classified by temperature and precipitation

disturbance

A natural or human-caused event that changes a biological community and usually removes organisms from it. Disturbances, such as fires and storms, play a pivotal role in structuring many communities.

thermocline

A narrow stratum of abrupt temperature change in the ocean and in many temperate-zone lakes.

dispersal

The movement of individuals or gametes away from their parent location. This movement sometimes expands the geographic range of a population or species.

tropical forest

A terrestrial biome characterized by relatively high precipitation and temperatures year-round.

savanna

A tropical grassland biome with scattered individual trees and large herbivores and maintained by occasional fires and drought.

desert

A terrestrial biome characterized by very low precipitation.

chaparral

A biome characterized by mild, rainy winters and long, hot, dry summers; dominated by dense, spiny evergreen shrubs

temperate grassland

A terrestrial biome that exists at midlatitude regions and is dominated by grasses and forbs.

temperate broadleaf forest

A biome located throughout midlatitude regions where there is sufficient moisture to support the growth of large, broadleaf deciduous trees.

northern coniferous forest

A terrestrial biome characterized by long, cold winters and dominated by cone-bearing trees.

tundra

A terrestrial biome at the extreme limits of plant growth. At the northernmost limits, it is called arctic tundra, and at high altitudes, where plant forms are limited to low shrubby or matlike vegetation, it is called alpine tundra.

density

The number of individuals per unit area or volume.

survivorship curves

A plot of the number of members of a cohort that are still alive at each age; one way to represent age-specific mortality.

exponential growth

Growth of a population in an ideal, unlimited environment, represented by a J-shaped curve when population size is plotted over time.

logistic growth

Population growth that levels off as population size approaches carrying capacity.

carrying capacity

The maximum population size that can be supported by the available resources, symbolized as K.

density dependent

Referring to any characteristic that varies with population density.

density independent

Referring to any characteristic that is not affected by population density.

K-selection

Selection for life history traits that are sensitive to population density; also called density-dependent selection.

r-selection

Selection for life history traits that maximize reproductive success in uncrowded environments; also called density-independent selection.

ecological footprint

The aggregate land and water area required by a person, city, or nation to produce all of the resources it consumes and to absorb all of the wastes it generates.

ecological succession

Transition in the species composition of a community following a disturbance; establishment of a community in an area virtually barren of life.

life history

The traits that affect an organism's schedule of reproduction and survival.

interspecific interaction

A relationship between individuals of two or more species in a community.

competition

Competition for resources between individuals of two or more species when resources are in short supply.

predation

An interaction between species in which one species, the predator, eats the other, the prey.

herbivory

An interaction in which an organism eats parts of a plant or alga.

symbiosis

An ecological relationship between organisms of two different species that live together in direct and intimate contact.

parasitism

A symbiotic relationship in which one organism, the parasite, benefits at the expense of another, the host, by living either within or on the host.

mutualism

A symbiotic relationship in which both participants benefit.

commensualism

A symbiotic relationship in which one organism benefits but the other is neither helped nor harmed.

facilitation

An interaction in which one species has a positive effect on the survival and reproduction of another species without the intimate association of a symbiosis.

competitive exclusion

The concept that when populations of two similar species compete for the same limited resources, one population will use the resources more efficiently and have a reproductive advantage that will eventually lead to the elimination of the other population.

resource partitioning

The division of environmental resources by coexisting species such that the niche of each species differs by one or more significant factors from the niches of all coexisting species.

niche

The sum of a species' use of the biotic and abiotic resources in its environment.

species diversity

The number and relative abundance of species in a biological community.

biomass

The total mass of organic matter comprising a group of organisms in a particular habitat.

trophic structure

The different feeding relationships in an ecosystem, which determine the route of energy flow and the pattern of chemical cycling.

food chain

The pathway along which food energy is transferred from trophic level to trophic level, beginning with producers.

food web

The interconnected feeding relationships in an ecosystem.

dominant species

A species with substantially higher abundance or biomass than other species in a community. Dominant species exert a powerful control over the occurrence and distribution of other species.

keystone species

Species having a disproportionate effect on the ecosystem

primary succession

A type of ecological succession that occurs in an area where there were originally no organisms present and where soil has not yet formed.

secondary succession

A type of succession that occurs where an existing community has been cleared by some disturbance that leaves the soil or substrate intact.

species-area curve

The biodiversity pattern that shows that the larger the geographic area of a community is, the more species it has.

pathogen

An organism, virus, viroid, or prion that causes disease.

ecosystem

All the organisms in a given area as well as the abiotic factors with which they interact; one or more communities and the physical environment around them.

law of conservation of mass

A physical law stating that matter can change form but cannot be created or destroyed. In a closed system, the mass of the system is constant.

primary production

The amount of light energy converted to chemical energy (organic compounds) by the autotrophs in an ecosystem during a given time period.

trophic efficiency

The percentage of production transferred from one trophic level to the next.

nitrogen cycle

The natural process by which nitrogen, either from the atmosphere or from decomposed organic material, is converted by soil bacteria to compounds assimilated by plants. This incorporated nitrogen is then taken in by other organisms and subsequently released, acted on by bacteria, and made available again to the nonliving environment.

bioremediation

The use of organisms to detoxify and restore polluted and degraded ecosystems.

biological augmentation

An approach to restoration ecology that uses organisms to add essential materials to a degraded ecosystem.

biological magnification

A process in which retained substances become more concentrated at each higher trophic level in a food chain.

ecosystem service

A function performed by an ecosystem that directly or indirectly benefits humans.

introduced species

A species moved by humans, either intentionally or accidentally, from its native location to a new geographic region; also called non-native or exotic species.

decomposer

An organism that absorbs nutrients from nonliving organic material such as corpses, fallen plant material, and the wastes of living organisms and converts them to inorganic forms; a detritivore.

primary consumer

An herbivore; an organism that eats plants or other autotrophs.

secondary consumer

A carnivore that eats herbivores.

tertiary consumer

A carnivore that eats other carnivores.

primary producer

An autotroph, usually a photosynthetic organism. Collectively, autotrophs make up the trophic level of an ecosystem that ultimately supports all other levels.

eutrophication

A process by which nutrients, particularly phosphorus and nitrogen, become highly concentrated in a body of water, leading to increased growth of organisms such as algae or cyanobacteria.

greenhouse effect

The warming of Earth due to the atmospheric accumulation of carbon dioxide and certain other gases, which absorb reflected infrared radiation and reradiate some of it back toward Earth.

ozone layer

Reduces the penetration of UV radiation through the atmosphere; eroded by chlorine-containing pollutants