IB Environmental Systems and Societies Definitions

First Law of Thermodynamics

"Energy may be transformed from one form to another, but cannot be created or destroyed."

Second Law of Thermodynamics

"In an isolated system, entropy tends to increase spontaneously."

Sustainable Development (1987 Definition)

'Development that meets current needs without compromising the ability of future generations to meet their own needs.'

Biome

A collection of ecosystems sharing similar climatic conditions; i.e. tundra, tropical rainforest, desert.

Competition

A common demand by 2 or more organisms upon limited supply of a resource; i.e. food, water, light, space, mates, nesting sites. It may be intraspecific or interspecific.

Ecosystem

A community of interdependent organisms and the physical environment they inhabit.

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.

Less Economically Developed Country

A country with low to moderate industrialization and low to moderate GNP per capita.

Demographic Transition Model

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 (i.e. those of North America, Europe, Australia) passed through the processes of industrialization and urbanization.

Diversity

A generic term for heterogeneity. The scientific meaning of the diversity becomes clease from the context in which it is used; it may refer to heterogeneity of species of habitat, or to genetic heterogeneity.

Population

A group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding.

Species

A group of organisms that interbreed and produce fertile offspring.

Community

A group of populations living and interacting with each other in a common habitat.

More Economically Developed Country

A highly industrialized country with high average GNP per capita.

Biotic Factor

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

Entropy

A measure of the amount of disorder, chaos or randomness in a system; the greater the disorder, the higher the level of entropy.

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

Correlation

A measure of the association between 2 variables. If 2 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.

Environmental Impact Assessment (EIA)

A method of detailed survey required, in many countries, before 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.

Soil

A mixture of mineral particles and organic material that covers the land, and in which terrestrial plants grow.

Abiotic Factor

A non-living, physical factor that may influence an organism or ecosystem; i.e. temperature, sunlight, pH, salinity, precipitation

Diversity Index

A numerical measure of species diversity that is derived from both the number of species (variety) and their proportional abundance.

Environmental Value System

A particular world view or set of paradigms which shape the way an individual or group of people perceive and evaluate environmental issues. This will be influenced by cultural, economic and socio-political context.

Pyramid of Productivity

A pyramid that represents the flow of energy through a trophic level and invariably show a decrease along the food chain.

Pyramid of Numbers

A pyramid that represents the numbers of individual plants and animals present in a food web.

Pyramid of Biomass

A pyramid that represents the standing stock of each trophic level measured in units such as grams of biomass per square metre (gm-2) or energy per square metre (Jm-2). It takes into account the body size of each organism, meaning the dry mass of each organism and its energy content must be calculated. A pyramid of biomass represents storages.

Parasitism

A relationship between 2 species in which one species lives in or on another, gaining all or much of its food from it.

Mutualism

A relationship between individuals of 2 or more species in which all benefit and none suffer.

Model

A simplified description designed to show the structure or workings of an object, system or concept.

Niche

A species' share of a habitat and the resources in it. Depends on where the specie lives and what it does.

Equilibrium

A state of balance among the components of a system.

Open System

A system in which both matter and energy are exchanged with its surroundings.

Closed System

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

Isolated System

A system that exchanges neither matter nor energy with its surroundings.

Natural Capital

A term sometimes used by economists for natural resources. If properly managed, renewable and replenishable resources are forms of wealth that can produce 'natural income' indefinitely in the form of valuable goods and services.

Soil Profile

A vertical section through a soil , from the surface down to the parent material, revealing the soil layers of horizons.

Society

An arbitrary group of individuals who share some common characteristics such as geographical location, cultural background, historical time frame, religious perspective, value system, etc,

System

An assemblage of parts and the relationship between them, which together constitute an entity or whole.

Global Warming

An increase in average temperature of the Earth's atmosphere.

Biodegradable

Capable of being broken down by natural biological processes; i.e. the activities of decomposer organisms

Positive Feedback

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

Negative Feedback

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

Pyramids

Graphical models of the quantitative differences that exist between the trophic levels of a single ecosystem.

Gaia

Hypothesis developed by James Lovelock and named after an ancient Greek Earth goddess. It compares the Earth to a living organism in which feedback mechanisms maintain 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 of child- bearing age. Alternatively it may be measured as total fertility, which is simply the average number of children a women has in her lifetime.

Non- Renewable Natural Capital

Natural resources that cannot be replenished within a timescale of that same order as that at which they are taken from the environment and used; i.e. fossil fuels.

Renewable Natural Capital

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

Replenishable Natural Capital

Non-living natural resources that depend on the energy of the Sun for their replenishment; i.e. groundwater.

Transformations

Processes that lead to an interaction within a system in the formation of a new end product, or involve a change of state. For example: evaporation.

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.

K- Strategist

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

Biosphere

That part of the Earth inhabited by organisms, that is, the narrow zone (a few km thick) in which plants and animals exist. It extends from the upper part of the atmosphere (where birds, insects and wind-blown pollen may be found) down to the deepest part of the Earth's crust to which living organisms venture.

Pollution

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 organism within it.

Biodiversity

The amount of biological or living diversity per unit area. It includes the concepts of species diversity, habitat diversity and genetic diversity.

Latitude

The angular distance from the equator (that is, north or south of it) as measured from the centre of the Earth (in degrees).

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 be the population, an the assimilation of all wastes.

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.

Secondary Productivity

The biomass gained by heterotrophic organisms, through feeding and absorption, measured in units of mass or energy per unit area per unit time.

Static Equilibrium

The condition in which there is no change in the system over time. A static equilibrium is a condition to which natural systems can be compared.

Stable Equilibrium

The condition of a system in which there is a tendency for it to return to a previous equilibrium condition following disturbance.

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.

Natural Increase Rate

The crude birth rate minus the crude death rate, excluding migration. A natural increase rate of 1% will make the doubling time of a human population 70 years.

Evolution

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.

Gross National Production (GNP)

The current value if all goods and services produced in a country per year.

Soil Degradation

The decline the quantity and quality of soil.

Habitat

The environment in which a species normally lives.

Rate of Natural Increase

The form in which human population growth rates are usually expressed: crude birth rate- crude death rate/ 10 (inward and outward migration are ignored)

Net Secondary Productivity

The gain by consumers in energy or biomass per unit time remaining after allowing for respiratory losses (R).

Net Primary Productivity

The gain by producers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses (R).

Primary Productivity

The gain by producers in energy or biomass per unit area per unit time. Can refer to either net or gross productivity.

Net Productivity (NP)

The gain in energy or biomass per unit area per unit time remaining after allowing for respiratory losses (R).

Flow

The inputs and outputs of a system.

Herbivory/Grazer Interactions

The interaction between a primary consumer (herbivore) and a producer.

Predation

The interaction between two organisms - the predator (which has a higher trophic level) and the prey (which has a lower trophic level). Predators differ from parasites in that they kill their prey before eating it.

Maximum Sustainable Yield

The largest yield (or catch) that can be taken from the stock of a species over an indefinite period.

Biomass/Standing Crop

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.

Carrying Capacity

The maximum number of species or "load" that can be sustainably supported by a given environment.

Plate Tectonics

The movement of the 8 major and several minor internally rigid plates of the Earth's lithosphere in relation to each other and to the partially mobile asthenosphere below.

Eutrophication

The natural or artificial enrichment of a body of water, particularly with respect to nitrates and phosphates, that result 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.

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.

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 approximately, that it, the doubling time for any human population is equal to 70 divided by the natural increase rate.

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.

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.

Isolation

The process by which 2 populations become separated by geographical, behavioral, genetic ore reproductive factors. If gene flow between the 2 subpopulations is prevented, new species may evolve.

Speciation

The process through which new species form.

Transfers

The processes that move through a system and produce a change in location but not a change in state or form. For example: run-off of water from a leaf to the ground.

Habitat Diversity

The range of different habitats or numbers of ecological niches per unit area in an ecosystem, community or biome. Conseravtion of habitat diversity usually leads to the conservation of species and genetic diversity.

Genetic Diversity

The range of genetic material present in a gene pool or population of a species.

Sustainable Yield

The rate of increase in natural capital which can be exploited without depleting the original stock or its potential for replenishment.

Point Source Pollution

The release of pollutants from a single, clearly identifiable site; i.e. a factory chimney

Non- Point Source Pollution

The release of pollutants from numerous, widely dispersed origins; i.e. gases from exhaust systems in vehicles.

Feedback

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

Sere

The set of communities that succeed one another over the course of succession at a given location.

Smog

The tern now used for any haziness in the atmosphere caused by air pollutants.

Gross Secondary Productivity (GSP)

The total gain by consumers in energy or biomass per unit area per unit time through absorption.

Gross Primary Productivity (GPP)

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

Gross Productivity (GP)

The total gain in energy or biomass per unit area per unit time, which could be through photosynthesis in primary producers or absorption in consumers.

Species Diversity

The variety of species per unit area. This includes both the number of species present and their relative abundance.

Greenhouse Gases

Those atmospheric gases which absorb infrared radiation, causing world temperatures to be warmer than they would otherwise be.

Sustainability

Use of global resources at a rate that allows natural regeneration and minimizes damage to the environment.

Halogenated Organic Gases

Usually known as halocarbons and first indentified as depleting the ozone layer in the stratosphere. Now known to be potent greenhouse gases. The most well known are chlorofluorocarbons.