In the r- and K-selection approach to classifying life history strategies, the selection pressures faced by organisms that live in environments where population densities are high (at or near the carrying capacity, K). Comparer-selection.
r-selection
In the r- and K-selection approach to classifying life history strategies, the selection pressures faced by organisms that live in environments where population densities are usually low. CompareK-selection.
allometry
Differential growth of body parts that results in a change of shape or proportion with size.
alternation of generations
A complex life cycle, found in many algae and all plants, in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte.
anisogamy
Production of two types of gametes of different sizes. Compare isogamy.
competitive plants
In Grime’s plant life history model, plants that are superior competitors under conditions of low stress and low disturbance. Compare ruderals, stress-tolerant plants.
complex life cycle
A life cycle in which there are at least two distinct stages that differ in their habitat, physiology, or morphology.
diapause
A state of suspended animation or dormancy in which an organism can survive unfavorable conditions.
direct development
A simple life cycle that goes directly from fertilized egg to juvenile without passing through a free-living larval stage.
disturbance
An abiotic event that kills or damages some organisms and thereby creates opportunities for other organisms to grow and reproduce.
endosperm
Nutrient-rich material in a seed that sustains the developing embryo and often the young seedling.
gametophyte
A multicellular haploid life cycle stage, found in many algae and all plants, that produces haploid gametes. Compare sporophyte, alternation of generations.
isogamy
The production of equal-sized gametes. Compare anisogamy.
iteroparous
Having the capacity to reproduce multiple times in a lifetime. Compare semelparous.
life history
A record of major events relating to an organism’s growth, development, reproduction, and survival.
life history strategy
The overall pattern in the timing and nature of life history events, averaged across all the individuals of a species.
metamorphosis
An abrupt transition in form from the larval to the juvenile life cycle stage that is sometimes accompanied by a change in habitat.
morphs
Discrete phenotypes with few or no intermediate forms.
ontogenetic niche
A size- or life cycle stage-specific ecological role.
optimal
Resulting in the maximization of fitness.
paedomorphic
Resulting from a delay of a developmental event relative to sexual maturation.
phenotypic plasticity
The ability of a single genotype to produce different phenotypes under different environmental conditions.
polyphenism
A type of phenotypic plasticity in which a single genotype produces multiple, discrete morphological forms.
reproductive effort
The quantity of energy and resources an organism devotes to reproduction.
ruderals
In Grime’s plant life history model, plants that are adapted to environments with high levels of disturbance and low levels of stress. Compare competitive plants, stress-tolerant plants.
semelparous
Reproducing only once in a lifetime. Compare iteroparous.
senescence
A decline in the fitness of an organism with age as a result of physiological deterioration.
sequential hemaphroditism
A change or changes in the sex of an organism during the course of its life cycle.
sporophyte
A multicellular diploid life cycle stage, found in many algae and all plants, that produces haploid spores. Compare gametophyte, alternation of generations.
stress
An abiotic factor that results in a decrease in the rate of an important physiological process, thereby lowering the potential for an organism’s survival, growth, or reproduction.
stress-tolerant plants
In Grime’s plant life history model, plants that are adapted to conditions of high stress and low disturbance. Compare competitive plants, ruderals.
trade-off
An organism’s allocation of its limited energy or other resources to one structure or function at the expense of another.
