Glossary

[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]

A

Abaptation
The process by which the present match between organisms and their environment, and the constraints on this match, have been determined by evolutionary forces acting on ancestors. The prefix 'ab-' emphasizes that the heritable characteristics of an organism are consequences of the past and not anticipation of the present or future.
Abiotic
Non-living; usually applied to the physical and chemical aspects of an organism's environment.
Abundance
The number of organisms in a population, combining 'intensity' (density within inhabited areas) and 'prevalence' (number and size of inhabited areas).
Acclimation
The habituation of an organism's physiological response to environmental conditions (usually applied to laboratory environments).
Acclimatization
The habituation of an organism's physiological response to environmental conditions (usually applied to natural environments).
'Acid rain'
Rain with a very low pH (often below 4.0) resulting from emissions to the atmosphere of oxides of sulfur and nitrogen.
Adaptation
A confusing word used to mean quite different things.
(i) Characteristics of organisms evolved as a consequence of natural selection in its evolutionary past and which result in a close match with features of the environment and/or constrain the organism to life in a narrow range of environments. The prefix 'ad-' is unfortunate as it implies that the process anticipates the present or the future (see Abaptation).
(ii) Changes in the form or behavior of an organism during its life as a response to environmental stimuli, e.g. the formation of sun and shade leaves on the same tree and the acquisition of cold tolerance as a result of prior experience of low temperatures.
(iii) Changes in the excitability of a sense organ as a result of continuous stimulation.
Adenosine triphosphate (ATP)
Molecule composed of adenine, ribose and three phosphate groups bound by high-energy linkages and associated with energy transfer in living cells.
Adiabatic expansion
Expansion taking place without heat entering or leaving the system.
Adventitious roots
Roots that arise in 'abnormal' positions, e.g. from a stem or leaf. The contrast is with the primary roots that develop from the axis of a seedling and roots that arise from other roots.
Aerobic decomposition
The process of breakdown of organic molecules to simple inorganic constituents when oxygen is in free supply.
Aesthetic injury level
The level of pest abundance above which aesthetic or sociological considerations suggest control measures should be taken against the pest.
Aestivation
A state of dormancy during the summer or dry season. (The word is also used by botanists to describe the arrangement of the parts in a flower bud.)
Aggregated distribution
The distribution of organisms in which individuals are closer together than they would be if they were randomly or evenly distributed.
Aggregation of risk
A pattern in which prey vary, from prey patch to prey patch, more than would be expected by chance alone in their risk of being attacked by a predator (especially applied to hosts varying in their risk of being attacked by parasitoids).
Aggregative response
The response of a predator through which it spends more time either in habitat patches with higher densities of prey, leading to higher densities of predators in patches with higher densities of prey, or in habitat patches with lower densities of prey, leading to higher densities of predators in patches with lower densities of prey. (See also Aggregation of risk.)
Alcohol dehydrogenase (ADH)
An enzyme catalysing the conversion of alcohols into aldehydes and ketones, and the reverse.
Allelochemical
A substance produced by one organism that is toxic or inhibitory to the growth of another.
Allochthonous material
Organic matter entering a stream, lake or ocean but derived from an adjacent terrestrial system.
Allogenic succession
A temporal succession of species at a location that is driven by external influences which alter conditions.
Allometry
The study of the changing proportions of the parts of an organism as size changes, either in individual growth (ontogenetic) or comparing related organisms of different sizes (phylogenetic).
Allopatry
Occurring in different places; usually refers to geographical separation of species.
Amensalism
An interaction in which one organism (or species) adversely affects a second organism (or species), but the second has no effect (good or bad) on the first.
Anaerobic decomposition
A process of breakdown of organic molecules to simpler inorganic constituents, that occurs in the absence of oxygen.
Analogous structures
Organs of different evolutionary origin which perform the same role in different organisms.
Angiosperms
Flowering plants. Strictly, those seed-bearing plants that develop their seeds from ovules within a closed cavity, the ovary (cf. gymnosperms, in which the ovules are naked).
Annual
A species with a life cycle which takes approximately 12 months or rather less to complete, whose life cycle is therefore directly related to the annual cycle of weather, and whose generations are therefore discrete.
Anoxic
Without oxygen.
Antagonistic resources
A pair of resources for which increased consumption by an organism of one resource leads to an increased requirement by that organism for the other.
Anthropocentric
Regarding humans as the central fact of the universe and interpreting everything in relation to them.
Aposematism
Conspicuous appearance of organism that is noxious or distasteful.
Apparent competition
An interaction in which the organisms (or species) have adverse effects on one another by virtue of the beneficial effects that each has on a predatory organism (or species) which they share.
Arthropod
A member of the animal phylum Arthropoda, which includes the insects, crustaceans (e.g. crabs, shrimps, barnacles), spiders, scorpions, mites, millipedes and centipedes.
Assimilation efficiency
The percentage of energy ingested by an animal that is absorbed across the gut wall.
Asymmetric competition
Competition between two organisms (or species) in which one is much more severely affected than the other.
Autochthonous material
Organic matter produced within a community (to contrast with allochthonous material that is produced outside it).
Autocidal control
A type of pest control in which the pest is manipulated so that it contributes significantly to its own control, or literally 'kills itself'.
Autogenic succession
A temporal succession of species at a location that is driven by processes operating within the community (in contrast with allogenic succession).
Autotroph
An organism that is independent of outside sources for organic food materials and manufactures its own organic material from inorganic sources.
Autotrophic succession
A temporal succession of species at a location principally involving plants.
Awn
A stiff bristle, especially on the grains of cereals and grasses.
Axillary bud
A bud produced in the angle between a leaf and the stem that bears it, i.e. the normal position of a lateral bud.

 
To the top

[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]