Glossary Flashcards
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
Abiotic Factors
A non-living, physical factor that may influence an organism or ecosystem; for example, temperature, sunlight, pH, salinity, precipitation
Biodegradable
Capable of being broken down by natural biological processes; for example, the activities of decomposed organisms
Biodiversity
The amount of biological or living diversity per unit area. It includes the concepts of species diversity and genetic diversity
Biomass
The mass 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 I organic 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
The paper 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; fro 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 for a resource; food, water, light, space, mates, nesting sites. It maybe 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 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 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 transition experienced as developed countries (for example, those of North America, Europe, Australasia) passed through the processes of industrialisation and urbanisation
Diversity
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
Genetic Diversity
The range of genetic material present in a gene pool or population of a species
Habitat Diversity
The range of different habitats or number of ecological a niches per unit in an ecosystem p, 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 derives from both the number of species (variety) and their proportional abundance.
Species Diversity
The variety of species per unit area. This includes both the number of species orders and their relative abundance
Doubling Time
The number of years it would take a population to double its size at it’s 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 real of land and water required to support a defined human population are a given standard of living. The measure takes account of the area require to provide all the resources needed by the population, and the assimilation of all wastes.
Ecosystem
A community of interdependent organism 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
Environmental Impact Assessment (EIA)
A method of detailed surgery required, in many countries befriend a major development. Ideally it should be independent of, but paid for by, the developer. Such a survey should include a baseline study to measure environmental conditions before development commences, and to identify areas and species of conservation importance. The report produced is know as an environmental impact statement (EIS) or environmental management review in some countries. The monitoring should continue for some time after the development.
Equilibrium
A state if balance among the components of a system
Eutrophication
The natural or artificial enrichment of a body of water, particularly with respect to nitrates and phosphates, that results in the depletion of the oxygen content of the water. Eutrophication is accelerated by human activities that add detergents, sewage or agricultural fertilisers to bodies of water.
Evolution
The cumulative, gradual change in the genetic characteristics of successive generations of an organisms, ultimately giving rise to species or races different from the common ancestor. Evolution reflects changes in the genetic composition of a population over time.
Feedback
The return of part of the output from a system as input, so as to affect succeeding outputs
Negative Feedback
Feedback that tends to damp down, neutralise or counteract any deviation from an equilibrium, and promotes stability
Positive Feedback
Feedback that amplifies or increases change; it lead to exponential deviation away from an equilibrium
Fertility
In the context of human populations, this refers to the potential for reproduction exhibited in a population. It may be measured as fertility rate, which is the number of births per thousand women child-bearing age. Alternatively it may be measured as total fertility, which is simply the average number of children a woman has in her lifetime.
Gaia Hypothesis
Developed by James Lovelock. It compare the earth to a living organism in which feedback mechanisms maintain equilibrium.