BISC104 Lecture Notes - Lecture 21: Peppered Moth, Genetic Variation, Selective Breeding

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How does evolution work?
Darwin proposed natural selection
Observed that organisms produce more offspring than the environment
can support
Organism’s vary
Inherited variation
Individuals compete
Environmental conditions cause non random survival and therefore
nonrandom reproduction
Concluded that individuals with some phenotypes (and therefore
genotypes) are more likely to survive and reproduce (evolutionary fitness)
Evolutionary fitness based on number of offspring
Those genetic traits (adaptations) become more common from one
generation to the next
Populations gradually change in response to the environment
Support from artificial selection→ humans choice of evolution
Example: dog breeding
Ancestral dog: wolf
Natural selection: five canine species evolving from one common ancestor
Lab experiments: measured % of population that metabolizes alcohol
Fly in normal environment:
generation 1-57 all had 10% metabolization
Fly in high-alcohol environment:
generation 1-57 dramatically increased to 100%, all of
population were able to metabolize
Support from wild populations
Peppered moth
From 1850 → industrial revolution → 1950
Most light-colored → most dark colored
Camouflage with tree (predator: bird)
Diversity is good
Importance of Genetic Variation
Phenotypic variation may be environmental or genetic in origin
But only genetic changes that result in evolutionary adaptation
Genetic variation comes from…
Mutation→ changes in nucleotide sequences
“Ultimate source” of genetic variation
Crossing over and independent assortment/random alignment
Sexual reproduction
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Document Summary

Observed that organisms produce more offspring than the environment can support. Environmental conditions cause non random survival and therefore nonrandom reproduction. Concluded that individuals with some phenotypes (and therefore genotypes) are more likely to survive and reproduce (evolutionary fitness) Evolutionary fitness based on number of offspring. Those genetic traits (adaptations) become more common from one generation to the next. Populations gradually change in response to the environment. Support from artificial selection humans choice of evolution. Natural selection: five canine species evolving from one common ancestor. Lab experiments: measured % of population that metabolizes alcohol. Generation 1-57 dramatically increased to 100%, all of population were able to metabolize. From 1850 industrial revolution 1950. Phenotypic variation may be environmental or genetic in origin. But only genetic changes that result in evolutionary adaptation. First occurs at random; mutation in nucleotide. Then, it continuously reproduces and will survive based off the environment.

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