The Mechanisms of Evolution Essential Question: How does evolution occur beyond Natural Selection?
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Transcript of The Mechanisms of Evolution Essential Question: How does evolution occur beyond Natural Selection?
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Just In Time Teaching
The Mechanisms of Evolution
Essential Question: How does evolution occur beyond Natural Selection?
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Populations and Their Gene Pools
• Gene Pool: consists of all the alleles in all the individuals that make up a population. This is where genetic variation is stored.
• You can think of a gene pool as the hat from which the next generation draws its genes.
A population is the smallest level at which evolution can occur. A common but mistaken belief is that individual
organisms evolve.
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• Genetic Drift: a change in gene pool of a population due to chance not natural selection.
• 2 types: The Bottleneck Effect & Founder Effect– All populations are subject to some genetic drift.– The smaller the population = the more impact genetic drift
has on that population.– Genetic drift can have major effects on a population.
• Example Natural Disaster Scenario
Genetic Drift
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Gene Flow • Gene Flow: exchange of genes with another population.• This takes place when fertile individuals or their
gametes migrate between populations.• Gene flow tends to reduce genetic differences between
populations.
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operates in populations where males and females differ significantly in appearance.
Qualities of sexual attractiveness appear to be the opposite of qualities that might enhance survival.
Sexual Selection (Nonrandom mating)
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Artificial Selection
• Artificial Selection: selective breeding of domesticated plants and animals to produce offspring with genetic traits that humans value– Humans have been modifying
species for thousands of years. Such as in dogs.
– Darwin observed that artificial selection could create change in a species over a short period of time.
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Evidence of speciation is visible in the 3 main patterns of evolutions:
Patterns of Evolution
1. Adaptive Radiation (Divergent Evolution)
2. Coevolution3. Convergent
Evolution
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Adaptive Radiation, also known as divergent evolution, occurs when many species diverge from one single ancestor.
Follows large-scale extinction events
Can occur in a relatively short time when one species
gives rise to many different species in response to the creation of new habitat or some other ecological opportunity
Adaptive Radiation
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Darwin’s Finches are an example of Adaptive Radiation
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Coevolution Coevolution occurs when
the relationship between two species might be so close that the evolution of one species affects the evolution of the other species.
• Examples include Mutualism, parasitism, and predator-prey relationships.
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Convergent Evolution• Convergent Evolution
occurs when unrelated species evolve similar traits even though they live in different parts of the world.
• The species have analogous structures.
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Evolution
Rate of Speciation:Gradualism
Evolution proceeds in small, gradual steps according to a theory called gradualism.
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Evolution
Punctuated equilibrium explains rapid spurts of genetic change causing species to diverge quickly.
Rate of Speciation:Punctuated Equilibrium
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How are the two models similar? Different?