Download Chapter 17 Evolution of Populations

17.2: Evolution as Genetic Change in
Populations
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1.
Evolutionary Fitness: passing genes on to next gen
Evolutionary Adaptation: genetic trait
indiv’s
ability to pass on alleles
Natural Selection on Single-Gene Traits:
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2.
Changes in allele freq=changes phenotype
Causes Genetic Change
Natural Selection On Polygenic Traits
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More complex
Can affect fitness of phenotypes to prod
1 of 3 types of selection
 Directional
 Stabilizing
 Disruptive
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Indiv at 1 end has fitness than at middle or end
Range of phenotypes shift b/c more successful at
surviving & reprod
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Indiv near center of curve have fitness than at ends
Keeps center of curve at current position
Narrows curve overall
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Indiv at outer ends of curve fitness than middle
Acts against indiv of intermediate type
Can use split of curve into 2
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1.
A change in gene pool (allele freq) due to chance
Genetic Bottlenecks:
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Reduction due to natural disasters & hunting
Reduce the size of pop
2.
The Founder Effect
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Few indiv colonize an isolated island, lake, or new habitat
Genetic makeup (
gene pool) diff from original colony
Change reduces genetic variation
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Genetic Equilibrium: allele freq in pop remain same
Hardy-Weinberg Principle: allele freq in pop remain constant
unless 1 or more factors cause freq to change
 5 conditions that cause evolution to occur:
1. Nonrandom Mating
2. Small Pop size
3. Immigration or Emigration
4. Mutations
5. Natural Selection
Hardy-Weinberg Formula
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Species: pop or grp of pop that can interbreed &
produce fertile offspring
Speciation: formation of new species
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Interbreeding genetically links members
Reproductive Isolation: 2 pop no longer interbreed, split
gene pool; evolve into 2 sep species
 Behavioral Isolation
 Geographic Isolation
 Temporal Isolation
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2 pop develop differences in courtship rituals or
other behaviors that prevent them from breeding.
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2 pop separated by geographic barriers ex: rivers,
mountains, water
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2 or more species reproduce at diff times  can not
interbreed
Ex: flowers bloom at diff times, can’t pollinate one
another