Transcript ppt

LAB:Variation in a Species
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What is the purpose of Part 1?
(Measuring Pumpkin seeds)
There is variation in size in Pumpkin plants.
Variation can be measured.
LAB:Variation in a Species
What is the purpose of Part 2?
(Calculate how long it takes pumpkin plants to take over
the Earth)
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There are reasons to explain why pumpkin
plants have not ever taken over the Earth
LAB:Variation in a Species
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What is the purpose of Part 3?
(Effect of predators on sweet cute Bonitos)
There are reasons to explain why the
population of bonitos on one island look
different from bonitos on another island
What is a species?
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A group of living things that
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are similar,
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and can breed together in nature
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to produce fertile offspring.
What is a population?
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A group of living things that
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belong to the same species,
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live in the same area,
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and can reproduce together.
What is a gene pool?
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The total collection of genes in a population
at any one time.
Hardy & Weinberg
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What is allele frequency?
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1908: Hardy and Weinberg invented the
term “allele frequency” to describe the
percentage of dominant and recessive
alleles found in a populaton.
Hardy & Weinberg
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How is allele frequency measured?
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Example: a lizard population might have the
following allele frequency for the alleles F
and f:
FF = 0.64
(64%)
Ff = 0.32
(32%)
ff = 0.04
(4%)
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Hardy & Weinberg
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What is genetic equilibrium?
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1908: Hardy and Weinberg invented the
term “genetic equilibrium” to describe a
population in which the frequency of
alleles stays the same from one generation
to the next.
Hardy & Weinberg
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How was genetic equilibrium measured?
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Hardy-Weinberg equations:
p2 + 2pq +q2 = 1
p+q=1
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Hardy & Weinberg
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Hardy-Weinberg Equations
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Where p2 is the frequency of homozygous
dominant individuals
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Where 2pq is the frequency of heterozygous
individuals
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Where q2 is the frequency of homozygous
recessive individuals
Hardy & Weinberg
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What causes genetic equilibrium?
There must be…….
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A large population
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Members mating at random
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No mutation
No migration
No natural selection
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Hardy & Weinberg
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What can cause allele frequency to change?
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Migration (also called gene flow)
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Mutation
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Mate selection (non-random mating)
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Predators, disease, famine, drought, storms,
accidents.