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Population density
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•the
number of individuals within a population per unit area
-High densities make it easier to find
mates, but increase competition, and vulnerability to predation
-Low densities make it harder to find
mates, but individuals enjoy plentiful resources and space
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Population distribution
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Spatial arrangement of organisms within an area.Random, uniform, and clumped
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Sex ratio
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Proportion of males to females
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Age structure
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The number of organisms of each age within a population.
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Crude birth/death rates
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Number of birth/deaths per 1,000 individuals in a given time period
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Survivorship curves
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The likelihood of death which varies with age.
-Type I: More deaths at older ages
-Type II: Equal number of deaths at all
ages
-Type III: More deaths at young ages
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Natality
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Births within a population
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Mortality
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Deaths within the population
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Immigration
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Arrival of individuals from outside the population
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Emigration
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Departure of individuals from the population
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Growth rate formula
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(crude birth rate +immigration rate)-(crude death rate +emigration rate)
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Exponential growth
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-
The increase of a population by a fixed percentage each year.
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Limiting factors
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•physical,
chemical and biological characteristics that restrain population growth
-Water, space, food, predators, and
disease
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Environmental resistance
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The collective force of limiting factors, which
together stabilize a population size at its carrying capacity.
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Density dependent factors
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•limiting
factors whose influence is affected by population density
- Increased risk of predation and
competition for mates occurs with increased density
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