IB Environmental Systems and Societies Definitions

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.
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.

Biotic factor

 

 

A living, biological factor that may influence an organism or ecosystem; for example, predation, parasitism, disease, competition.

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.

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.

Feedback, positive

 

 

Feedback that amplifies or increases change; it leads to exponential deviation away from an equilibrium.

K -strategist

 


Species that usually concentrate their reproductive investment in a small number of offspring, thus increasing their survival rate and adapting them for living in long?term climax communities.

Feedback, negative

 

 

Feedback that tends to damp down, neutralize or counteract any deviation from an equilibrium, and promotes stability.

Feedback

 

 

The return of part of the output from a system as input, so as to affect succeeding outputs.

Mutualism
A relationship between individuals of two or more species in which all benefit and none suffer.

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.

Natural capital, renewable

 

 

Natural resources that have a sustainable yield or harvest equal to or less than their natural productivity; for example, food crops, timber.

Natural capital, replenishable

 

 

Non?living natural resources that depend on the energy of the Sun for their replenishment; for example, groundwater.

Natural capital, non-renewable

 

 

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.

Niche

 

 

A species’ share of a habitat and the resources in it. An organism’s ecological niche depends not only on where it lives but also on what it does.

Pollution

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The addition to an environment of a substance or an agent (such as heat) by human activity, at a rate greater than that at which it can be rendered harmless by the environment, and which has an appreciable effect on the organisms within it.

Pollution, non-point source

 

 

The release of pollutants from numerous, widely dispersed origins; for example, gases from the exhaust systems of vehicles.

Pollution, point source

 

 

The release of pollutants from a single, clearly identifiable site; for example, a factory chimney or the waste disposal pipe of a factory into a river.

Productivity, gross primary (GPP)

 

 

The total gain in energy or biomass per unit area per unit time fixed by photosynthesis in green plants.

r -strategist

 

Species that tend to spread their reproductive investment among a large number of offspring so that they are well adapted to colonize new habitats rapidly and make opportunistic use of short-lived resources.

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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.

System, closed

 

 

A system in which energy, but not matter, is exchanged with its surroundings.