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Ecology Intro

Definitions encountered during 3rd year Zoology module on Ecology

Terms

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Environmental condition
An abiotic environmental factor that varies in space and time and to which organisms responde differently (e.g. temperature, relative humidity, pH, salinity, pollution, currents, etc)
Resource
Things that can be depleted through the activity of the organisms and there is therefor less to be used by others. (Could be food or something an organism absorbs, or an ecological factor such as a nest site etc)
Acclimation
response to change in condition occurs after exposure to that condition in the laboratory
Secondary Succession
the series of changes that occur after a disturbance of an existing ecosystem, A type of succession that occurs where an existing community has been cleared by some disturbance that leaves the soil intact.
n-curve
Describes the density dependent effect of intraspecific competition on net recruitment (births - deaths) of a population
Ecology
The scientific study of the interactions that determine the distribution and abundance of organisms
primary succession
when a disturbance occurs and there is no soil so things can barely grow, colonization of new land that is exposed by avalanches, valcanoes, or glaciers by pioneer organisms.
Law of constant yield
The yield (mass/weight per unit area) of a population is constant over a wide range of densities. Density dependent reductions in growth rate compensate for any increase in density.
Resource-weighted density
Number of individuals per resource unit
life tables
a table of data summarizing mortality in a population
Delayed density dependence
Delayed regulatory effect that predator has on prey population, when abundance of both are closely linked together
Ectotherm
Regulate body temp by making use of external sources of heat
Type 3 functional responce
High prey density makes finding prey easier & handling time by predators is longer. At high prey densities, consumers spend more time handling prey due to increased competition for prey. With low prey densities, accelerated phase is evident (absent in type 2 responce) where an increase in density leads to a more linear increase in consumption rate. type 3 responce is typically sigmoidal or S-shaped.
Iteroparity
A life history in which adults produce large numbers of offspring over many years; also known as repeated reproduction.
Thermoneutral Zone
Range of environmetal temperatures at which an endotherm does not have to actively regulate its body temperature
density independent factors
factors which effect a population the same regardless of population size (fire, pH, temperature)
Endotherm
Regulate body temp by making use of heat produced by their own bodies
Allee's Principle (Allee Effect)
effect that occurs when individuals in a population have a disproportionately low rate in recruiment when their own density is low. This may be due to dofficulty in finding mates, or critical number needed to exploit resouce properly. Effect may be graphically represented as a "hump" in prey isocline.
Competition as enemy-free space
When a predator uses 2 species as a resouce, enemy free space can then be regarded as a resouce competed for by both prey species. Any adaptation to escape from the predator can be seen as a competitive advantage.
Carrying Capacity
The maximum number of individuals of a given species that a particular environment can support for an indefinite period, assuming there are no changes in the environment
Acclimatization
exposure of organisms to a climatic condition in a natural environment in the past, which then influences the responce of the organism to that condition in the future (e.g. exposure to low temp)
Density dependent factors
are limiting factors that are affected by the number of individuals in a given area.
Interference competition
Individuals of a species directly & physically interfere for the exploitation of a resouce. Sometimes territoriality may come into play.
Semelparity
A life history in which adults have a single reproductive opportunity to produce large numbers of offspring, such as the life history of the Pacific salmon
Character displacement due to interspecific competition
Measurable physical difference between 2 species which has arisen by natural selection as a result of the selection pressures on one or both from competition with the other. Niche differentiation plays an NB role to result in morphological changes in the course of evolution
Cohort
Group of individuals recorded from time of birth until death.

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