Download Genetic drift

UNIT 6 - Evolution
9.10.2
SWBAT identify other evolutionary
mechanisms of natural selections and
compare them with natural selection
What is this bid doing and why?
• http://www.youtube.com/watch?v=8tO80BvZ
apA
IBE - JTPS
• Have you ever wondered why many male
birds, such as cardinals, are brightly colored
while females of the same species are dull
brown?
J-TPS (Justify –Think Pair Share)
THINK
PAIR
SHARE
Natural selection is not the only mechanism
through which populations evolve
Mechanisms for evolution
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Gene flow
Genetic drift
Sexual Selection
Mutation
Speciation
Natural selection
Mechanisms for evolution
• Gene flow
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•
•
•
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Genetic drift
Sexual Selection
Mutation
Speciation
Natural selection
Gene flow is the movement of
alleles between populations
• Gene flow increases genetic variation
What are
alleles?
Mechanisms for evolution
• Gene flow
• Genetic drift (founder effect and
bottleneck effect)
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•
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Sexual Selection
Mutation
Speciation
Natural selection
Genetic Drift
The process of allele frequency change (evolution) in a
population due to chance or random events
Genetic drift can be expressed as a
“bottleneck effect”
• It is usually as a result of a catastrophe or unforeseen
event
Genetic drift can also be caused by
the “Founder Effect.”
• It occurs after a small number of individuals colonize a
new area.
Mechanisms for evolution
• Gene flow
• Genetic drift
• Sexual Selection
• Mutation
• Speciation
• Natural selection
Sexual selection occurs when certain
traits increase mating success
• Intrasexual - involves competition between males
Sexual selection
• Intersexual - involves traits that attract the opposite sex
White board
A change in the allele frequency due to
migration (individual coming in or out) in a
population is called?
1. genetic drift
2. sexual selection
3. bottleneck effect
4. gene flow
White board
The five factors that can lead to evolution are
gene flow, genetic drift, mutation, natural
selection, and
1. sexual selection
2. controlled mating
3. emigration
4. immigration
White board
________ changes allele frequencies due to
chance alone
1. Natural selection
2. Gene flow
3. Genetic drift
4. Mutations
Critical thinking
• How does gene flow affect neighboring
populations?
Critical thinking
• How does gene flow affect neighboring
populations?
• Gene flow decreases genetic diversity
between neighboring populations.
Critical thinking
• Would a population of 10 individuals or 100
individuals be more vulnerable to genetic
drift? Why?
Critical thinking
• Would a population of 10 individuals or 100
individuals be more vulnerable to genetic
drift? Why?
• A smaller population is more vulnerable to
genetic drift because it has a smaller gene
pool and is therefore more likely to be
affected by chance events.
IBE - JTPS
• Have you ever wondered why many male
birds, such as cardinals, are brightly colored
while females of the same species are dull
brown? Such bright coloring may not make
sense in terms of natural selection, since the
male birds are more likely to be seen by
predators. However, natural selection is not
the whole story.