Lesson 6: Mechanisms of Evolution
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Microevolution – when the ____________ of an allele in a population changes
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What are the factors that lead to microevolution???
1.
2.
3.
4.
5.
1. Mutation
DNA change in an individual
• _______________________ may contribute to gene pool
• i.e. Norway: rats and warfarin poison resistance – selective advantage
2. Gene Flow
What is it?
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The net ______________ of alleles from _____ population to ____________ due to the
migration of individuals
Movement of individuals & alleles _____ & ____________________
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seed & pollen distribution by wind & insect
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migration of animals
_____________ differences between populations
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Human evolution today
➢ Gene flow in human population is _____________ today
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Transferring alleles between populations
3. Non-random Mating
What is it?
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Mating among individuals on the basis of mate selection for a particular phenotype or due to
inbreeding
Where do you see this?
____________________: prevents particular phenotypes from being bred
_______________
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: closely related individuals breed together
__________ genotypes ->______________ genotypes increase
i.e. self-fertilization flowers
i.e. animals: health problems
4. Gene Drift
Effect of _______________
➢ The ___________ the sample size the ______________the chance of uncertainty
• Less likely that gene pool will be seen in the next generations
➢ __________________
small group splinters off & starts a new colony
➢ _________________
Some factors (disaster) reduces population to small
number & then population
recovers & expands
a) Founder effect
➢ When a new population is started by only a few individuals – ____________
❖ Some __________ alleles may be at ___________ frequency; others may be
_____________
❖ Skew the ______________ of new population
Human populations that started from ___________ group of colonists
i.e. colonization of New World
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b) Bottleneck effect
➢ When a large population is drastically ______________________
❖ Famine, natural disaster, loss of habitat…
❖ Loss of variation by __________________
• alleles lost from gene pool
₋ not due to ____________
_________________________________
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➢ Typhoon 1775 – Pingelap
survivors <30/1600
1 survivor had color blindness
today= 10% color vision deficiency in the island
➢ 2 bottlenecks
• 10,000 years ago
• Ice age
• last 100 years
• poaching & loss of habitat