The study of ancient ecosystems. Paleoecologists use data from such sources as tree rings, geologic deposits, fossils (pollen is a particularly popular tool), and coral bores to reconstruct the climate and ecology or ancient ecosystems.

Particulate matter

Fine solid or liquid particles that pollute the air and are added to the atmosphere by natural and man-made processes at the Earth’s surface. Examples of particulate matter include dust, smoke, soot, pollen and soil particles.



Land that is used to, or has the potential, to produce food for grazing animals
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A government grant of temporary monopoly rights on innovative processes or products.


A disease causing microorganism, bacterium or virus.


A causal agent of disease.


The downward movement of water through soil under the influence of gravity


A plant that lives for more than two years


A pesticide is any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest. Pests can be insects, mice and other animals, unwanted plants (weeds), fungi, or microorganisms like bacteria and viruses. Though often misunderstood to refer only to insecticides, the term pesticide also applies to herbicides, weedicides, fungicides, and various other substances used to control pests (USEPA, 1997).

Pesticide Residue

A detectable level of a chemical residue in food product

Pesticide Tolerance Levels

Scientifically acceptable level of a pesticide residue that can exist on a fruit or vegetable product. Usually expressed in parts per million or billion.


A general term for any chemicals that are used to kill weeds, fungi, insects or other pests.



The observable appearance of an organism, as determined by environmental and genetic influences (in contrast to genotype).

Phosphorus cycle

Cyclic movement of phosphorus, in varying chemical forms, from the environment to organisms and then back to the environment.


The process plants use to change air and water into food, using the sun's energy.


Pertaining to the evolutionary history of a particular group of organisms.


In taxonomy, a high-level category just beneath the kingdom and above the class; a group of related, similar classes.


Chemicals found naturally in plants.

Pioneer species

First hardy, often xerophytic species (often microbes, mosses, and lichens) that begin colonizing a site as the first stage of ecological succession.


The transfer of pollen from an anther to a stigma of a flower of the same species.


An animal that carries pollen, such as insects, birds, or bats.


An alteration of the natural environment producing a condition that is harmful to living organisms


Trait a trait controlled by multiple genes.


A compound consisting of repeated linked monomers

Polymerase chain reaction (PCR)

Technique used to quickly make many copies of selected segments of DNA


A long chain of several amino acids


A segment of the brain stem


A group of individuals with common ancestry those are much more likely to breed with one another than with individuals from another such group.

Population and Habitat Viability Assessment (PHVA)

The theoretical modelling of minimum areas, habitat types and population sizes, to sustain any one or more species. Population size will be determined by the carrying capacity of the habitat.

Population change

An increase or decrease in the size of a population. It is equal to (births immigration) - (deaths emigration).

Population density

Number of organisms in a particular population found in a specified area.

Population dispersion

General pattern in which the members of a population are arranged throughout its habitat.

Population distribution

Variation of population density over a particular geographical area. For example, a country has a high population density in its urban areas and a much lower population density in rural areas.

Population Viability Analysis (PVA)

The theoretical determination of the minimum viable (in terms of genetic make-up) breeding population for any one species to survive in a given range.

Power-take-off (PTO)

A powered shaft, usually extending from the rear of the tractor and driven by the tractor motor, to supply rotative power to an attached or trailing implement such as a combine, hay baler, mower, etc.


An animal that obtains its food primarily by killing and consuming other animals.

Primary (or natural) forest

A forest largely undisturbed by human activities.

Primary producer

An organism, such as a plant or microbe, that makes its own food and forms the bottom-most tier in a trophic system. Primary producers are the basis of the food web in most ecosystems Primary producers are able to convert abiotic raw materials into biotic tissue, either by capturing the sun's energy through photosynthesis (plants) or by harnessing the energy in chemical bonds through chemosynthesis (some microbes).

Primary productivity

The transformation of chemical or solar energy to biomass. Most primary production occurs through photosynthesis, whereby green plants convert solar energy, carbon dioxide, and water to glucose and eventually to plant tissue. In addition, some bacteria in the deep sea can convert chemical energy to biomass through chemosynthesis.

Protected Area (PA)

An area of land and/or sea especially dedicated to the protection and maintenance of biological diversity, and of natural and associated cultural resources, and managed through legal or other effective means.

Provinciality effect

Increased diversity of species because of geographical isolation.

Pyramid of biomass

Diagram representing the biomass (total dry weight of living organisms) that can be supported at each trophic level in a food web. The bottom of the pyramid is comprised of primary producers , while the peak of the pyramid is topped by one (or at most a small handful) apex predator . Humans are abnormal in that we cross all ecosystems and biomass pyramids, and in almost every one (excepting the polar caps and deepest of oceanic environments) we are the dominant apex predator.

Pyramid of energy flow

Also called a trophic pyramid . Diagram representing the flow of energy through each trophic level in a food chain or food web. With each energy transfer, only a small part (typically 10%) of the usable energy entering one trophic level is transferred to the organisms at the next trophic level, with the remaining 90% lost as heat or expended in metabolic processes.