Download But what drives change in a gene pool of a population?

Mechanisms of Evolution
Guided Notes
EVOLUTION
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A change in ___________________ ___________________________ in a population over time
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There are different alleles for dark moths and light moths (B= dark, b= speckled)
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When pollution changes the environment, dark moths became more common, which means the allele
that causes dark coloring became more frequent.
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This is _____________________________________!
What is a population?
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All the same species
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Live in the same place at the same time
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Can _________________________
Populations evolve, NOT _____________________________!
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The genetics of a population can change based on genetic ____________________ that exist within a population
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Variations are caused by sexual reproduction and mutations
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One individual cannot change its ___________________
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Evolution changes the gene pool of a population over generations
Gene Pool
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A GENE POOL - all of the ____________________ of the populations’ genes together in one large “pool”
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The larger the population the __________________ the gene pool
Allelic Frequency
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The percentage of any specific allele in the gene pool is called the ALLELIC FREQUENCY (ie: 70% dark alleles)
Genetic Equilibrium
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GENETIC EQUILIBRIUM refers to a population in which the frequency of alleles remains the ___________ over
generations.
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No ______________, so no evolution
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You can use the Hardy-Weinberg equation to calculate the frequency of alleles in a population at equilibrium:
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p² + 2pq + q² = 1
But what drives change in a gene pool of a population?
MECHANISMS OF EVOLUTION: HOW IT HAPPENS…
Mechanisms of evolution: Natural Selection
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___________________ exists among individuals in a species. (Variation comes from mutations and sexual
reproduction mixing genes from mom and dad)
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Some variations are ____________________ and will help them compete better
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Individuals that had advantageous variations are more likely to _____________________ and reproduce, while
others without the variation are more likely to die (competition)
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Over time, advantageous variations are passed down to future generations, changes accumulate and
___________________________ change
Mechanisms of Evolution: Sexual Selection
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Evolution of traits based on the ability to find mates
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Traits will not help an individual survive, but will make them more likely to _________________________ and
pass on their genes to future offspring
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Proposed by Charles Darwin in addition to his theory of Natural Selection
Phenotype/genotype
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Natural selection and sexual selection work on the _______________________________ of organisms
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Individuals with phenotypes that are better able to survive or attract mates will pass on their genetic
information (genotypes) to their offspring
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Since phenotype is determined by genotype, the alleles of a population will change as phenotypes change
Mechanisms of evolution: Genetic Drift
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A mechanism that can change a population’s genetic equilibrium is GENETIC ___________________
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The alteration of allelic frequencies by chance events (not selection)
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Affects _________________ populations (small gene pools)
Mechanisms of evolution: Gene Flow (Migration)
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Genetic Equilibrium is also disrupted by the movement of individuals in and out of a population.
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The transport of _________________ by migrating individuals is called GENE FLOW
Mechanisms of Evolution: Population Bottleneck
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If a population is reduced to just a few individuals, there is less genetic variation
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Their offspring will also have __________ genetic variation
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Genetic drift, gene flow, and population bottlenecks can significantly affect the evolution of small and isolated
populations
Results of Evolution
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Changes in existing species, or possibly…
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Entirely NEW species (Speciation)
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Occurs when members of similar populations can no longer interbreed and produce fertile offspring