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]
[N] [O] [P] [Q] [R] [S] [T] [U] [V] [W] [X] [Y] [Z]
N
- n-dimensional hypervolume
- see Ecological niche.
- 'n'-shaped curve
- More correctly, 'unimodal': a curve with a single maximum.
- Natural selection
- The force that causes some individuals in a population to contribute more descendants (and genes) than others to subsequent generations and so leads to changes in the genetic composition of populations over time (evolution). (See also Fitness.)
- Necromass
- The weight of dead organisms, usually expressed per unit of land or volume of water. The term is sometimes used to include the dead parts of living organisms, e.g. the bark and heartwood of trees, the hair and claws of animals.
- Necroparasite
- A parasite that kills its host (or a part of it) and continues growth on the dead resource.
- Net primary production (NPP)
- The total energy accumulated by plants during photosynthesis (gross primary production minus respiration).
- Neutral models
- Models of communities that retain certain features of their real counterparts but exclude the consequences of biotic interactions; they are used to evaluate whether real communities are structured by biotic forces.
- Neutralism
- The lack of an interaction between two organisms (or species): neither has any effect on the other.
- Niche
- The limits, for all important environmental features, within which individuals of a species can survive, grow and reproduce.
- Niche complementarity
- The tendency for coexisting species which occupy a similar position along one niche dimension, e.g. altitude, to differ along another, e.g. diet.
- Niche differentiation
- The tendency for coexisting species to differ in their niche requirements.
- Niche packing
- The tendency for coexisting species between them to fill the available 'space' along important niche dimensions.
- Nitrification
- The conversion of nitrites to nitrates, usually by microorganisms. The term is commonly used to describe the process of conversion of ammonium ions via nitrites to nitrates.
- Nitrogen fixation
- The conversion of gaseous nitrogen (N2) into more complex molecules. The process is used industrially to produce nitrogen fertilizers. Biological nitrogen fixation is accomplished by both free-living and symbiotic microorganisms (prokaryotes). The process is more properly called 'dinitrogen fixation'.
- Node
- The place on a stem where one or more leaves arise.
- Non-equilibrium theory
- In community ecology, concerned with the transient behavior of a system away from any equilibrium point, it specifically focuses attention on time and variation.
- Null hypothesis
- The hypothesis that an observed pattern of data and an expected pattern are effectively the same, differing only by chance, not because they are truly different. A statistical significance test is then generally applied to the data to test whether the hypothesis can be rejected. If so, the observed and expected patterns are said to be significantly different. Tests do not establish that the null hypothesis is true. 'Expected' patterns may be derived from theory or from other, related data sets.
- Nunatak
- Islands standing out in a 'sea of ice' during periods of glaciation and in which species may have persisted.
- Nutrient cycling
- The transformation of chemical elements from inorganic form in the environment to organic form in organisms and, via decomposition, back to inorganic form.
