# BISC 102 Lecture Notes - Lecture 16: Logistic Function, Local Extinction, Anthropocene

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21 Apr 2016
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Individuals in a population use common resources, cope with similar environmental
factors, and interact with one another and with their environment.
Population Ecology: Variation in space
individuals vary through space
○ Demography: The statistical study of how population size/structure change
over time. (Population Structure)
Life Table: A summary of deaths/survivors at various age classes for
a population
Population characteristics
Range: Geographic area a population resides in
○ Dispersion: Pattern of spacing between individuals
Clumped: Individuals aggregated into patches
Uniform or Regular: Individuals evenly spaced (maintain individual
distance)
■ Random: Unpredictable spacing of individuals. It occurs when biotic
and abiotic conditions are relatively homogenous
○ Size: number of individuals
Small populations can be counted directly
Larger populations are estimated using sampling
● Sampling: counting a proportion of the population to estimate
the total number of individuals per unit area
Quadrat sampling: Organisms that are sessile (e.g. plants,
barnacles) or slow moving (e.g. sea stars)
● Quadrat: Sampling area of any size or shape (e.g. 1 m2 )
q/Aq = N/Ap
q = average # individuals per quadrat
Aq = area of the quadrat (cm2 , m2 )
Ap = area inhabited by the population (same units!)
N = estimated population size
Mark recapture sampling: Used to estimate the population of mobile
animals.
○ Density: number of individuals per unit area
Age structure: number of individuals of different ages
Sex ratio: ratio of males to females
Survivorship curves (logx )
Survival patterns can be tabulated using life tables, and presented as survivorship
curves
Type 1: mortality increases with age
Type 2: mortality is constant over time
Type 3: mortality decreases with age
Correlated life history traits: Survivorship is often correlated with other aspects of life
history.
Strategy A
Breed young
Many small babies
Little parental care
Die young
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