Transcript Analyze and evaluate the effects of other evolutionary

Unit 11
7F
Analyze and evaluate the effects of
other evolutionary mechanisms,
including genetic drift, gene flow,
mutation, and recombination.
Let’s remember…
• An allele is an alternative form of one gene
B stands for black b stands for brown
The allele would be…
Genetic Drift
• An evolutionary mechanism in
which allele frequencies change
in a population
Allele frequency changes due to…
• Natural disaster like flood, fire, or
earthquake
• A random change of the
population (some are eliminated)
• Different from natural selection
b/c its by chance or randomly
Original Pop
Pop after change
R = red star r = green heart
6R, 5r
5r
Bottleneck Effect
• The change in allele frequency
where only genes of the surviving
population members can be
passed to future generations
Gene Pool
• the sum of all the genes in an
interbreeding population
Gene Pool
• 2 blue alleles
• 1 red allele
• 12 green alleles
Founder Effect
• The change in allele frequency in a
gene pool that changes from a large
population to a small population
• Ex: small number of individuals get
separated from a larger population…
the change in the allele frequency is
the founder effect
Founder Effect
Gene Flow
• Occurs when the genes of 1
population flow into a different
population
• This change causes a shift in
allele frequency
Immigration
• Alleles move INTO a population
Emigration
• Alleles move OUT OF a population
Lots of gene flow…
• Slows down evolution
• Lots of new alleles coming into
and out of a population
• More genetic variation within a
population
• Makes 2 populations more similar
Lack of gene flow…
• Less variation within a population
• Makes 2 populations more
different and separates them
Mutation
• Any change in the genetic
material of a cell
• Can occur within individual genes
OR
• Can involve changes in piece of
chromosomes
• If the mutation is beneficial to the
organism, the mutation will be
passed on to offspring
• Slowly over time the mutation
will become more common in a
population
Recombination
• A source of heritable variation
• Occurs for 2 reasons:
a. Independent assortment
b. Crossing over
Independent Assortment
Crossing Over
Hardy-Weinberg Principle
• States that allele frequencies in a
population will remain constant
unless one ore more factors
cause those frequencies to
change
Hardy-Weinberg Equation
Homozygous
dominant
2
P
Heterozygous Homozygous
recessive
+ 2pq +
2
q
= 1
p = dominant allele frequency
q = recessive allele frequency
Genetic Equilibrium
• The situation in which allele
frequencies remain constant
(don’t change)
• If frequencies don’t change, the
population doesn't evolve
Conditions required to maintain
genetic equilibrium:
1.
2.
3.
4.
5.
Random mating
Population must be large
No immigration or emigration
No mutations
No natural selection