FacilitationEnhancement of conditions for a population of one species by the activ-
ities of another, particularly during early succession.
FecundityThe potential reproductive capacity of an organism, measured by the num-
ber of gametes produced.
FertilityAn ecological concept of the actual number of viable offspring produced by
an organism, equivalent to realized fecundity.
Finite rate of increase (λλ)The ratio of the population density in one year to that
in the previous year (Nt/Nt− 1 ). (Cf. exponential rate of increase, intrinsic rate of
increase.)
FitnessThe genetic contribution by an individual’s descendants to future genera-
tions of a population relative to that of other individuals.
Food chainThe sequence of energy or nutrient transfer through the trophic levels,
beginning with plants and ending with the largest carnivores.
Food webA representation of the various paths of energy flow through populations
in a community; the complex of food chains.
FragilityReferring to a habitat with narrow tolerance to disturbance. (Cf. resilience,
robust.)
Functional responseA change in the rate of exploitation of prey by an individual
predator as a result of a change in prey density. (Cf. numerical response.)
Fundamental nicheSee niche.Gamma diversityThe average diversity per habitat (alpha) ×1/the mean number of
habitats occupied by a species (beta) ×the total number of habitats.
Gause’s principleSee competitive exclusion principle.
GeneA unit of genetic inheritance. (i) In biochemistry, the part of the DNA
molecule that encodes a single enzyme or structural protein. (ii) In evolutionary
ecology, that which segregates independently.
Generation timeThe average age at which a female gives birth to her first offspring,
or the average time for a population to increase by a factor equal to the net repro-
ductive rate.
GenotypeEntire genetic constitution of an organism. (Cf. phenotype.)
Global stabilityAbility to withstand perturbations of a large magnitude and not be
affected. (Cf. local stability.)
Grazers(i) Organisms that eat grasses or non-woody herbs. (ii) Organisms that feed
on many other individuals but usually do not kill them. (Cf. browsers.)
Gross productionProduction before respiration losses are subtracted; photosynthetic
production for plants and metabolizable production for animals.HabitatThe place where an animal or plant normally lives, often characterized by
a dominant plant form or physical characteristic (e.g. soil habitat, forest habitat).
HarvestingRemoving animals or plants from a population, usually by humans.
HelminthsMembers of the five classes of parasitic worms: Monogenea, Digenea,
Cestodes, Nematodes, and Acanthocephalans.
HerbivoreOrganism that eats plants. (Cf. carnivore.)
HerbivoryA consumer–resource interaction involving the consumption of plants or
plant parts.
HeterosisA situation in which the heterozygous genotype is more fit than either
homozygote.GLOSSARY 393
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