Download AP Biology Jones The components to the Hardy

AP Biology
Jones
The components to the Hardy-Weinberg principle explain reasons why a population would maintain genetic
equilibrium (not evolve) unless acted upon by an outside factor. Fill in the table below to explain how
these outside influences allow the evolution of a population (change allele frequencies).
List
Genetic Drift
(This is listed under “Large
Population” in the H-W
Principle. But, discussing
Genetic Drift is the
pertinent information needed
to be discussed; population
size should be addressed)
a.
Founder affect
b. Bottleneck affect
Types of Selection
a. Natural selection
Describe
Random loss of alleles by
chance.
When a new colony is started by
a few members of the original
population colonizing new
habitats.
Results from reduction of
population’s size. Usually a
natural disaster
Differential success in the
reproduction of different
phenotypes. Environment
selects more favorable alleles.
Effect
Allele frequencies fluctuates; how
much depends on population size:
- Large populations tend to stay
more stable due to more
alleles in gene pool.
- Small populations don’t have
many alleles in gene pool, so
losing large number alleles will
drastically affect allele
frequencies.
• Decreased genetic
diversity
• Decreased genetic diversity
•
Surviving population doesn’t
genetically represent the original
population’s diversity.
•
Environmental selective pressures
choose favorable alleles.
Organisms with more favorable
alleles have higher reproductive
success = fitness.
More fit traits passed on
Allele frequencies change towards
favorable, fit alleles
•
•
•
b. Sexual Selection
c.
Directional Selection
d. Stabilizing Selection
Female = choice
- More energy invested
per egg, per offspring
Males = compete to be chosen.
Natural selection that favors
individuals at one end of the
phenotypic range
•
Favorable traits selected are
represented in offspring.
• Greater reproductive success for
offspring.
Shifts to variation at edges of
variation range; shifts away from
Natural selection that favors
intermediate variants by acting
against extreme phenotypes.
Trends toward narrow range of
phenotype; favors intermediate area
of phenotypic range.
average phenotype
.
e.
Disruptive Selection
Migration
Mutation
Non-Random Mating (Sexual
Selection)
Natural selection that favor
individuals on both extremes of
a phenotypic range over
intermediate phenotypes
• Immigration = New alleles
entering a population
• Emigration = Alleles leaving
a population
• Changes nucleotide sequence
of a gene or genes.
This component is discussed in
“types of selection”, so no need
to describe this as a separate
influence on allele frequencies.
Favors variants at both ends of range;
intermediate phenotype is less
favorable.
•
•
•
•
•
Adds variation
May decrease variation
Some are neutral
Some are fatal
Some are favorable