Glossary

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C

Caecum
A blindly ending sac at the junction between the small and large intestines.
Calcareous
Composed of, or containing lime or limestone.
Capture - recapture
A method for estimating the size of populations of mobile organisms (usually animals), in which one or more samples are captured, marked and released, and one or more samples examined for the proportion of recaptured marks (broadly speaking, high in small populations and low in large).
Carbohydrase
An enzyme that acts on carbohydrate.
Carbon (C) 3 plants
Those in which the assimilation of atmospheric carbon dioxide is directly via the enzyme ribulose-1,5-bisphosphate carboxylase in the cells of the leaf mesophyll.
Carbon (C) 4 plants
Species of higher plants in which the assimilation of atmospheric carbon dioxide in the photosynthetic process is indirect, via the enzyme phosphoenol pyruvate carboxylase in the sheaths surrounding the veins of the leaves.
Carboniferous period
Geological period from c. 270 to 220 million years ago.
Carnivory
The consumption by an organism of living animals or parts of living animals.
Carrying capacity
The maximum population size that can be supported indefinitely by a given environment, at which intraspecific competition has reduced the per capita net rate of increase to zero. An idealized concept not to be taken literally in practice.
Catabolism
The decomposition by living organisms of complex organic molecules to simpler forms, with the release of energy.
Catastrophe
A major change in the environment that causes extensive damage and usually widespread death, and occurs so infrequently that the effects of natural selection by similar events in the past (if they have ever occurred) do not remain in the 'genetic memory' of the species. The Mt St Helens volcanic eruption was in this sense a catastrophe (cf. the recurrent hurricanes in eastern USA which may be defined as 'disasters').
Catch per unit effort
Usually applied to the harvesting of a natural resource (e.g. marine fish), the total catch (in terms of numbers or biomass) divided by the total harvesting effort (e.g. a product of the total number and size of ships and the number of days that they fished).
Cellulolytic enzymes
Enzymes that act on cellulose.
Cellulose
A complex polymer of glucose molecules. The fundamental cell wall constituent in all green plants.
Census
In ecology, an attempt to count every member of a population.
Chaos
Applied to a time-series of population abundance or density, a pattern in which elements of the pattern are never repeated exactly, and where two very similar abundances in the time-series follow trajectories subsequently which diverge from one another exponentially. Nonetheless, the series is not random and fluctuates within definable limits.
Chaparral
A thicket of low evergreen oaks or dense tangled brushwood.
Character displacement
A measurable physical difference between two species which has arisen by natural selection as a result of the selection pressures on one or both from competition with the other.
Chemosynthesis
The synthesis of organic molecules by certain bacteria that use the energy released by specific inorganic molecules.
Chlorophyll
Green pigment(s) found in almost all plants and playing a crucial role in the capture of radiant energy in the process of photosynthesis.
Chloroplast
The inclusions (plastids) within plant cells which contain chlorophyll.
Classification
A mathematical procedure for categorizing communities in which communities with similar species compositions are grouped together in subsets.
Climax
The presumed endpoint of a successional sequence; a community that has reached a steady state.
Clonal dispersal
The movement or growth away from each other of the parts of a modular organism (commonly, but not necessarily, becoming detached from each other).
Clone
The whole product of growth from a single zygote, in organisms that grow by the repeated iteration of units of structure (modular organisms) and in which the units have, at least potentially, the capacity for physiological independence. The parts of a clone are genetically identical except for what are probably rare somatic mutations.
Clumped distribution
The distribution of organisms in which individuals are closer together than if they were distributed at random or equidistant from each other. (= Aggregated distribution.)
Coefficient of interference
A measure of the extent to which interference amongst consumers increasingly depresses individual consumption rates as consumer density increases.
Coefficient of variation
A statistical term, referring to the standard deviation of a distribution divided by the distribution's mean, and hence providing a standardized measure of the variation in a distribution, which does not increase simply because the mean itself increases or because the units of measurement change.
Coevolution
The process by which members of two (or more) species contribute reciprocally to the forces of natural selection that they exert on each other, e.g. parasites and their hosts.
Coexistence
The living together of two species (or organisms) in the same habitat, such that neither tends to be eliminated by the other. This begs lots of questions about the meaning of 'living together' and the 'same habitat'.
Cohort generation time (Tc)
An approximation to the true generation length, which takes no account of the fact that some offspring may themselves develop and give birth during the reproductive life of the parent; hence, simply the average time between the birth of a parent and the birth of its offspring.
Cohort life table
A life table constructed by monitoring a group of individuals all born during the same short period, from this time of birth through to the death of the last surviving individual.
Collector - filterers
Aquatic animals that filter small particles of organic matter from the water flowing over them.
Collector - gatherers
Aquatic animals that gather small particles of organic matter from the sediment.
Colonization
The entry and spread of a species (or genes) into an area, habitat or population from which it was absent.
Commensalism
An interaction in which one organism (or species) beneficially affects a second organism (or species), but the second has no effect (good or bad) on the first.
Community
The species that occur together in space and time.
Community stability
The tendency of a community to return to its original state after a disturbance.
Community structure
The list of species and their relative abundances in a community.
Compartmentalization in communities
A tendency in communities to be organized into subunits within which interactions are strong but between which interactions are weak.
Compensation point
The intensity of radiation at which photosynthesis equals and balances respiration.
Competition
An interaction between two (or more) organisms (or species), in which, for each, the birth and/or growth rates are depressed and/or the death rate increased by the other organisms (or species).
Competition coefficient
In interspecific competition, a measure of the competitive effect of one species on another relative to the competitive effect of the second species on itself.
Competitive exclusion
The elimination from an area or habitat of one species by another through interspecific competition.
Competitive exclusion principle
see Gause's principle.
Competitive release
The expansion of the niche of a species associated with the lack of competition with other species; for instance, because it occurs on an island where competitors are absent.
Complementarity
A condition of two resources of which less is required when they are taken together than when consumed separately.
Complementary resources
A pair of resources for which consumption by the consumer of one resource reduces the consumer's requirements for the other.
Conservation
The principles and practice of the science of preventing species extinctions.
Conspecific
Belonging to the same species.
Consumption efficiency
The percentage of energy available that is actually consumed at a trophic level. In the case of herbivores it is the percentage of net primary productivity that is ingested.
Contest competition
Intraspecific competition in which mortality compensates exactly for increases in density, so that there are a constant (or approximately constant) number of survivors irrespective of initial density.
Continental drift
The separation and movement of land masses in geological time.
Continentality
Climatic conditions associated with locations in the middle of large continents.
Control action threshold (CAT)
The combination of pest density and the densities of the pest's natural enemies beyond which it is necessary to intervene and take control measures against the pest, to prevent its population rising to a level at which it will cause economic damage.
Convergent evolution
The process by which organisms of different evolutionary lineages come to have similar form or behavior.
Coprophagy
The consumption of feces.
Correlogram
A statistical procedure for the analysis of time-series data and to test for the presence of cyclic phenomena.
Coupled oscillations
Linked fluctuation in the abundance of two species, broadly speaking a 'predator' and a 'prey', in which low prey abundance leads to low predator abundance which leads to high prey abundance, which leads to high predator abundance which leads to low prey abundance, and so on.
Crassulacean acid metabolism (CAM)
A pathway for the assimilation of carbon dioxide by plants, in which carbon dioxide is fixed into organic acids during the night and released during the day for photosynthesis. Characteristic of succulent desert plants.
Cretaceous period
A geological era; the final part of the Mesozoic, from approximately 140 to 170 million years ago.
Crypsis
Form or behavior of an organism that makes it difficult to detect, e.g. camouflage from a predator.
Cuticle
In plants, a layer of waxy substance on the outer surface of epidermal cell walls. In animals, the outermost layer of many invertebrates.
Cyanogenic
Releasing hydrogen cyanide.
Cytoplasm
The living matter within a cell, excluding the genetic material.

 
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