Transcript DISRUPTING GENETIC EQUILIBRIUM

Hardy-Weinberg Genetic Equilibrium
Hardy-Weinberg equilibrium describes
populations that are not evolving
 Genotype frequencies stay the same over time
as long as certain conditions are met:

 Very
large populations
 No
emigration or immigration
 No
mutations
 Random
 No
mating
natural selection
DISRUPTING GENETIC
EQUILIBRIUM
Ch. 16-2 pp. 321-325
Definitions..

Evolution is the change in a population’s
genetic material (alleles) over
generations.
Definitions..
Evolution is the change in a population’s
genetic material (alleles) over
generations.
 A population is in genetic equilibrium if
it’s not evolving

WHAT PUSHES A POPULATION OUT OF
EQUILIBRIUM?
Population is in
equilibrium
5 Factors
I. Mutation

Produces and introduces new alleles in a population
II. Migration/ Gene Flow

Movement of individuals in or out of a population
 Immigration
– In (Entering population)
 Emigration – Out (Leaving population)
III. Genetic Drift

The amount of an allele changes due to random events
Population of the nearly extinct northern Elephant Seal have lost genetic
variability—individuals are homozygous for all their genes tested. This
result of genetic drift makes the species vulnerable to extinction.
III. Genetic Drift


The amount of an allele changes due to random events
Affects small populations mostly
Population of the nearly extinct northern Elephant Seal have lost genetic
variability—individuals are homozygous for all their genes tested. This
result of genetic drift makes the species vulnerable to extinction.
III. Genetic Drift
The amount of an allele changes due to random events
Affects small populations mostly
Lose alleles if not enough to mate or a catastrophe occurs
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EX: tornado, disease, hurricane etc.
Population of the nearly extinct northern Elephant Seal have lost genetic
variability—individuals are homozygous for all their genes tested. This
result of genetic drift makes the species vulnerable to extinction.
IV. Natural Selection (3 Types)

Organisms best suited to their environment live to
reproduce and pass on their genes
IV. Natural Selection (3 Types)


Organisms best suited to their environment live to
reproduce and pass on their genes
Acts on a phenotype
IV. Natural Selection (3 Types)



Organisms best suited to their environment live to
reproduce and pass on their genes
Acts on a phenotype
Varying types of selection
1. Directional Selection
Individuals with a more extreme form of trait have
higher fitness
Suppose termites in an
area begin to build
deeper nests.
Anteaters with long
tongues could more
effectively prey on
termites than those
with short or average
tongue length
Normal Distribution
Distribution after Selection
2. Stabilizing Selection
Having average form of trait has highest fitness
Blue curve shoes
variation after a new
predator is introduced.
Predator can easilty
capture the large,
visible lizards and the
small slower lizards.
Thus, selection against
these extremes body
types reduces the size
range in lizards
Normal Distribution
Distribution after Selection
3. Disruptive Selection
Individuals with any extreme trait has a higher fitness
and most likely results in two new species
The white limpets
blend in with
barnacles on rocks. On
bare rocks, darkshelled limpets blend
in. However, the tan
colored limpets are
easy to spot by birds.
Normal Distribution
Distribution after Selection
V. Non-random mating

Can amplify certain traits and reduce others through
sexual selection
V. Non-random mating


Can amplify certain traits and reduce others through
sexual selection
Sexual Selection - Choose mates based on specific
traits and those traits increase in the population
Class work


Create 4-squares for the following words
Use page 325
 Directional
Selection
 Stabilizing Selection
 Disruptive Selection
def
Example
Graph
Word
2 associated phrases (description)
Homework
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WS #2