BIO 115 Lecture Notes - Lecture 2: Population Ecology, Natural Selection

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23 Jun 2018
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2. Ecology: Population
Population
oGroup of interbreeding individuals occupying the same habitat at the same time
oEvolve as a whole
oIndividuals = natural selection
oVariation arise from mutation
Population ecology
oStudy of how populations grow and what promotes and limits growth
Natural selection patterns
oDirectional Selection
Most common during periods of environmental change or when members
of a population migrate to a new habitat with different environmental
conditions
An extreme phenotype is favored over other phenotypes causing the allele
frequency to shift over time in the direction of that phenotype
oDiversifying Selection
Occurs when environmental conditions favor individuals at both extremes
of the phenotypic range
Result in balanced polymorphism
Balanced polymorphism- two or more alleles are kept in balance
and therefore are maintained in a population over the course of
many generations
oStabilizing Selection
Favors the survival of individuals with intermediate phenotypes
Extreme values of a trait are selected against
oDisruptive Selection
Favors the survival of two or more different genotypes that produce
different phenotypes
Diverse environments
Members can freely interbreed
oBalancing Selection
Maintains genetic diversity
Balanced polymorphism
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Document Summary

Population: group of interbreeding individuals occupying the same habitat at the same time, evolve as a whole o. Individuals = natural selection: variation arise from mutation. Population ecology: study of how populations grow and what promotes and limits growth. Most common during periods of environmental change or when members of a population migrate to a new habitat with different environmental conditions. An extreme phenotype is favored over other phenotypes causing the allele frequency to shift over time in the direction of that phenotype: diversifying selection. Occurs when environmental conditions favor individuals at both extremes of the phenotypic range. Balanced polymorphism- two or more alleles are kept in balance and therefore are maintained in a population over the course of many generations: stabilizing selection. Favors the survival of individuals with intermediate phenotypes. Extreme values of a trait are selected against: disruptive selection. Favors the survival of two or more different genotypes that produce different phenotypes. Members can freely interbreed: balancing selection.

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