Endotherm

An organism that generates and regulates its own body temperature, in particular birds and mammals. Compare with ectotherm.

  Environment

The surroundings, and extent of the surroundings within a stated boundary, in which organisms and abiotic (non-living) matter exists. An organism’s environment consists of prevailing conditions, such as temperature or soil pH, and resources which can be consumed by an organism, such as nutrients or water.

  Enzymes

These are large molecules which help to increase the speed of chemical reactions.

  Ephemeral

A plant that completes its life cycle in short time period; being less than a growing season. There may also be more than one life cycle achieved within a year. An ephemeral plant can also be considered a short-term annual. A number of weeds are ephemeral plants, including: • Groundsel (Senecio vulgaris). • Common Chickweed (Stellaria media). • Hairy Bittercress (Cardamine hirsuta). • Thale Cress (Arabidopsis thaliana). • Annual Meadow Grass (Poa annua), which can often behave as an ephemeral.

  Epidermis

A layer of plant cells which are one cell in thickness and form the outer layer of plant organs. Stomata are present within the epidermis, acting as the conduit for gas exchange with the atmosphere and for the loss of water vapour due to evapo-transpiration.

  Eudicots

The main group (Clade) of flowering plants (Angiosperms) which were formerly classified as Dicotyledons. These are plants that have embryos that normally have two cotyledons (hence 'di'). They typically have the following characteristics: • They can possess cambium and secondary thickening and can be woody or herbaceous plants. • The floral parts are grouped in 4s or 5s. • They have a persistent primary root which develops into a thick taproot; lateral roots develop from the taproot. • The root and stem vascular bundles are arranged in ring formation. • The major leaf veins are netlike in appearance.

  Eukaryotes

Organisms that have cells with a nucleus enclosed within membranes: These types of cells are found in organisms within the Animal, Fungi and Plant Kingdoms. Compare with Prokaryotes.

  Eutrophication

The build-up of nutrients, especially nitrogen and phosphorus, in water sources. This often leads to algal blooms, a toxic water source, and a reduction and death of fish as well as poisoning of animals which drink the water. Excess and inappropriate fertiliser application for the soil type can lead to run-off and leaching into water courses.

  Evapo-Transpiration

The amount of water lost from the soil and plant through the combined processes of evaporation and transpiration. It is often abbreviation to E-T.

  Family

A taxonomic category that is used to group organisms. Families are grouped from similar Genera, with a plant Family often being considered the highest natural grouping for identification purposes. Similar Families are in turn grouped into an Order.