Glossary Terms

Abiotic Factor
A non-living, physical factor that may influence an organism or ecosystem;
for example, temperature, sunlight, pH, salinity, precipitation.
Biochemical oxygen demand
A measure of the amount of dissolved oxygen required to break down the
organic material in a given volume of water through aerobic biological
Capable of being broken down by natural biological processes; for
example, the activities of decomposer organisms.
The amount of biological or living diversity per unit area. It includes the
concepts of species diversity, habitat diversity and genetic diversity.
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.
A collection of ecosystems sharing similar climatic conditions; for
example, tundra, tropical rainforest, desert.
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
A group of populations living and interacting with each other in a
common habitat.
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.
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
Crude birth rate The number of births
Crude birth/death rate
The number of births/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, Australasia) passed through the processes of
industrialization and urbanization
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
Habitat Diversity
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 index
A numerical measure of species diversity that is derived from both the
number of species (variety) and their proportional abundance.
Species Diversity
A numerical measure of species diversity that is derived from both the
number of species (variety) and their proportional 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.)
A community of interdependent organisms and the physical environment
they inhabit.
Entropy A measure of the amount
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 survey required, in many countries, before a
major development.Such a survey should include a baseline study to
measure environmental conditions before development commences,
and to identify areas and species of conservation importance.
A state of balance among the components of a system.
The natural or artificial enrichment of a body of water, particularly with
respect to nitrates and phosphates, that results in depletion of the oxygen
content of the water. Eutrophication is accelerated by human activities
that add detergents, sewage or agricultural fertilizers to bodies of water.
The cumulative, gradual change in the genetic characteristics of successive
generations of a species or race of an organism, ultimately giving rise to
species or races different from the common ancestor. Evolution reflects
changes in the genetic composition of a population over time.
The return of part of the output from a system as input, so as to affect
succeeding outputs.
Feedback, negative
Feedback that tends to damp down, neutralize or counteract any
deviation from an equilibrium, and promotes stability.
Feedback, positive
Feedback that amplifies or increases change; it leads to exponential
deviation away from an equilibrium.
It may be measured as fertility
rate, which is the number of births per thousand women of 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.
The Gaia hypothesis compares the Earth to a living organism in which feedback mechanisms maintain equilibrium
Global warming
An increase in average temperature of the Earth’s atmosphere
Gross National Product, the current value of all goods and services
produced in a country per year.
Greenhouse gases
Those atmospheric gases which absorb infrared radiation, causing world
temperatures to be warmer than they would otherwise be (global warming). The natural greenhouse effect
is caused mainly by water and carbon dioxide, human-made carbon dioxide, methane, NOx in the atmosphere.
The environment in which a species normally lives.
Halogenated organic gases
Usually known as halocarbons that deplete the ozone
layer in the stratosphere (e.g. CFCs)
The process by which two populations become separated by
geographical, behavioural, genetic or reproductive factors. This leades to interrupted gene flow and evolution of new species.
Species that usually concentrate their reproductive investment in a small
number of offspring, thus increasing their survival rate and live in climax communities.
The angular distance from the equator ( north or south of it) as
measured from the centre of the Earth
Less economically developed country: a country with low to moderate

and low to moderate average GNP per capita.

More economically developed country: a highly industrialized country

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with high average GNP per capita.

A simplified
designed to show the structure or workings of an
object, system or concept.
A relationship between individuals of two or more species in which all
benefit and none suffer. (The term symbiosis will not be used.)
Natural capital
A term sometimes used by economists for natural resources that, if
appropriately managed, can produce a “natural income” of goods and
services. The natural capital of a forest might provide a continuing natural
income of timber, game, water and recreation
Non-renewable Natural Capital
Natural resources that cannot be replenished within a timescale of the
same order as that at which they are taken from the environment and
used; for example, fossil fuels.
Renewable Natural Capital
Natural capital that has a sustainable yield that is less than or equal to or less than natural productivity: LIKE TIMBER OR SUNLIGHT
Replenishable Natural Capital
NON-living natural resources that depend on the energy of the sun
Natural Increase
The rate of increase in population as defined by (crude birth – crude death)/10
An organism’s share of a natural habitat and the resources shared within it. An ECOLOGICAL niche is the role of the organism in that habitat
A relationship between an organism and its host where much of its food is gained from it.
Plate tectonics
The movement of the earth’s eight major and several minor plates of the lithosphere in relation to each other and to the partially mobile asthenosphere below.
The addition of a substance or an agent by human activity at a rate that is faster than the rate that the environment can render it harmless, and has a n appreciable effect on its inhabitants.
Non-point source Pollution
Pollution from widely-dispersed sources (car exhaust)
Point source- pollution
The release of pollutants from a clearly identifiable site
The group od organisms of the same species living at the same area at the same time, which are capable of interbreeding
Gross Primary Prductivity
The total gain in biomass fixed by green plants
Gross productivity
The TOTAL GAIN in biomass or energy per unit area per unit time, which could be through photosynthesis in primary producers or absorption through consumers
Gross secondary productivity
The total amount of biomass fixed per unit area per unit time through absorption
Net productivity
The gain in biomass per unit area per unit time after allowing respiratory losses
Net primary Productivity
The gain in biomass per unit area per unit time by autotrophs after allowing respiratory losses and are available to the next trophic level
Net secondary productivity
The gain in biomass/area/time after allowing repiratory losses by consumers after allowing respiratory losses
A species that tend to spread their reproductive investment over a large amount of offspring so that they make opportunistic use of the short-lived resources and colonize a new habitat
The set of communities that succeed one another over thr course of succession over a period of time
The hazziness in the atmosphere caused by air pollutants. Photochemical smog is caused by the action of UV light on the products of internal combustion engines that cause respiratory and optical irritation
An arbitrary group of individuals who share similar characteristics such as geographical location, cultural/ religious ,/ social / political value systems
The part of the lithosphere covered by mineral and organic particles where plants grow. It is created by the physical, chemical, and biological action on rocks over a long period of time.
Soil Profile
The vertical section of a soil from surface to parent material revealing soil horizons
The process through new species occur
The group of individuals that are capable of interbreeding
Stable equilibrium
The state of an ecosystem that has the tendency to return to a previous equilibrium condition following a disturbance
Steady-state equilibrium
The condition of an open system where there are no changes on the slong term but many oscillations in the short term. There are continuous inputs and outputs of energy, but the system more or less remains in a constant state.
The orderly process of change in a community. This change often results in the physical change in the environment,allowing another community that is often more complex to establish themselves over the previous community via competition.
The use of natural resources at a rate that allows natural regeneration and minimizes damage to the environment.
The arrangement or patterning of plant communities or ecosystmes in parallel bands in response to change, over distance, in some environmental factor.
EG: biomes of the world change according to latitude and climate, the plants on a mountain change according to altitude, while the plants around a pond might change according to moisture