p

ecological dictionary

P

Pacana

An Aztec word describing a North American tree that measures up to 30 meter in height. Its wood is similar to the wood of walnut trees.

Peat

Fossil material formed by partially carbonized vegetable matter. It can be used as fuel when dried.

Permaculture

A term coined by Hill Mollison in the 1970s derived from “permanent” and “agriculture.” Permaculture does not deal with specific agricultural techniques, but with how to create an ecosystem in which people, animals, plants and land can interact in the most effective and sustainable way.

Pesticide

Any substance used to control pests. This includes herbicides, insecticides, fungicides and others. Unfortunately, many pesticides are transported by air, or may leak into waterways, with potential deleterious effects for humans and the environment.

pH

A measure of the acidity or alkalinity of a liquid. pH stands for pouvoir hydrogène – French for hydrogen power. Acidity and alkalinity are measured on the pH scale, which runs from 1 to 14. A solution is called acidic if it has a pH value lower than 7, and alkaline (or basic) if it has a pH value higher than 7. (See also Acidity and Alkalinity.)

Phyllophagous

Feeding on leaves.

Photosynthesis

A biochemical process in which light energy from the sun is absorbed and transformed into chemical energy in green plants.

Phototropism

The reaction of a plant to light.

Phytoplankton

Very small unicellular organisms that carry chlorophyll and float in the water.

Plankton

Large groups of tiny organisms, such as plants (phytoplankton) or animals (zooplankton), which float and drift in fresh or salt water.

Population density

The number of organisms in a defined area.

Protozoans

One-celled animals that are so small they can only be seen through a microscope. They live in almost any medium, including water, humid land, organic material, plants, blood, human intestines, and in animals. They are very important ecological components, for instance by controlling bacteria, or as an important food source for small microorganisms. Some well known protozoans are pathogenic to humans, include malaria parasites and trypanosomes (which cause trypanosomiasis or sleeping sickness).

a | b | c | d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z