ESS Glossary Flashcards
Zonation
The arrangement or patterning of plant communities or ecosystems into parallel or sub - parallel bands in response to change, over a distance, in some environmental factor. The main biomes display zonation in relation to latitude and climate. Plant communities may also display zonation with altitude on a mountain, or around the edge of a pond in relation to soil moisture
Trophic level
The position that an organism occupies in a food chain, or a group of organisms in a community that occupy the same position in food chains.
System, open
A system in which both matter and energy are exchanged with its surroundings (for example, natural ecosystems).
System
An assemblage of parts and the relationships between them, which together constitute an entity or whole.
System, isolated
A system that exchanges neither matter nor energy with its surroundings.
System, closed
A system in which energy, but not matter, is exchanged with its surroundings.
Sustainability
Use of global resources at a rate that allows natural regeneration and minimizes damage to the environment. For example, a system of harvesting renewable resources at a rate that will be replaced by natural growth might be considered to demonstrate sustainability.
Succession
The orderly process of change over time in a community. Changes in the community of organisms frequently cause changes in the physical environment that allow another community to become established and replace the former through competition. Often, but not inevitably, the later communities in such a sequence or sere are more complex than those that appear earlier.
Steady - state equilibrium
The condition of an open system in which there are no changes over the longer term, but in which there may be oscillations in the very short term. There are continuing inputs and outputs of matter and energy, but the system as a whole remains in a more or less constant state (for example, a climax ecosystem).
Abiotic factor
A non-living, physical factor that may influence an organism or ecosystem; for example, temperature, sunlight, pH, salinity, precipitation.
Biochemical oxygen demand (BOD)
A measure of the amount of dissolved oxygen required to break down the organic material in a given volume of water through aerobic biological activity.
Biodegradable
Capable of being broken down by natural biological processes; for example, the activities of decomposer organisms.
Biodiversity
The amount of biological or living diversity per unit area. It includes the concepts of species diversity, habitat diversity and genetic diversity.
Biomass
The mass of organic material in organisms or ecosystems, usually per unit area. Sometimes the term “dry weight biomass” is used where mass is measured after the removal of water. Water is not organic material and inorganic material is usually relatively insignificant in terms of mass.
Biome
A collection of ecosystems sharing similar climatic conditions; for example, tundra, tropical rainforest, desert.
Biosphere
That part of the Earth inhabited by organisms, that is, the narrow zone (a few kilometres in thickness) in which plants and animals exist. It extends from the upper part of the atmosphere (where birds, insects and windblown pollen may be found) down to the deepest part of the Earth’s crust to which living organisms venture.
Biotic factor
A living, biological factor that may influence an organism or ecosystem; for example, predation, parasitism, disease, competition.
Carrying capacity
The maximum number of a species or “load” that can be sustainably supported by a given environment.
Climax community
A community of organisms that is more or less stable, and that is in equilibrium with natural environmental conditions such as climate; the end point of ecological succession.
Community
A group of populations living and interacting with each other in a common habitat.
Competition
A common demand by two or more organisms upon a limited supply of a resource; for example, food, water, light, space, mates, nesting sites. It may be intraspecific or interspecific.
Correlation
A measure of the association between two variables. If two variables tend to move up or down together, they are said to be positively correlated. If they tend to move in opposite directions, they are said to be negatively correlated.
Crude birth rate
The number of births per thousand individuals in a population per year.
Crude death rate
The number of deaths per thousand individuals in a population per year.
Demographic transition
A general model describing the changing levels of fertility and mortality in a human population over time. It was developed with reference to the transition experienced as developed countries (for example, those of North America, Europe, and Australasia) passed through the processes of industrialization and urbanization.
Diversity
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A generic term for heterogeneity. The scientific meaning of diversity becomes clear from the context in which it is used; it may refer to heterogeneity of species or habitat, or to genetic heterogeneity
Diversity, genetic
The range of genetic material present in a gene pool or population of a species.
Diversity, habitat
The range of different habitats or number of ecological niches per unit area in an ecosystem, community or biome. Conservation of habitat diversity usually leads to the conservation of species and genetic diversity.
Diversity index
A numerical measure of species diversity that is derived from both the number of species (variety) and their proportional abundance.
Diversity, species
The variety of species per unit area. This includes both the number of species present and their relative abundance.
Doubling time
The number of years it would take a population to double its size at its current growth rate. A natural increase rate of 1% will enable a human population to double in 70 years. Other doubling times can then be calculated proportionately, that is, the doubling time for any human population is equal to 70 divided by the natural increase rate.
Ecological footprint
The area of land and water required to support a defined human population at a given standard of living. The measure takes account of the area required to provide all the resources needed by the population, and the assimilation of all wastes. (A method of calculation is provided in 3.8.2.)
Ecosystem
A community of interdependent organisms and the physical environment they inhabit.
Entropy
A measure of the amount of disorder, chaos or randomness in a system; the greater the disorder, the higher the level of entropy.