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Lecture 2

BIO220H1 Lecture Notes - Lecture 2: Galactose, Starch, Diarrhea


Department
Biology
Course Code
BIO220H1
Professor
Nicole Mideo
Lecture
2

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1/7/2015
1
Lecture 2: Human – Agricultural
Coevolution
ecofriend.com smartcanucks.ca 2
General Outline
What is coevolution?
How do humans coevolve with agricultural
species?
What imprint does such coevolution leave in
genomes?
3
Coevolution
Reciprocal evolutionary responses in:
– a pair of species, caused by selection imposed by
each other
Wol ves
Moose
Selection
Wol ves
Evolutionary
response
Wol ves
Selection
Moose
Selection
Moose
Evolutionary
response
Etc.
Moose
Evolutionary
response
4
Sexual Coevolution
Reciprocal evolutionary responses in:
– the two sexes, caused by selection imposed by
each other
Females Females Females
Males Males Males
Selection
Evolutionary
response
Selection Selection
Evolutionary
response
Etc.
Males
Evolutionary
response
5
Human Agricultural Coevolution
Reciprocal evolutionary responses in:
– humans and their agricultural species, caused by
selection imposed by each other
Humans Humans Humans
Cows Cows Cows
Selection
Evolutionary
response
Selection Selection
Evolutionary
response
Etc.
Cows
Evolutionary
response
6
General Outline
What is coevolution?
How do humans coevolve with
agricultural species?
What imprint does such coevolution leave in
genomes?
two species evolve with each other interactively
human impose selection on them; also vice versa
genetic hitchhiking, evolutionary stages

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1/7/2015
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7
Human-Agricultural Coevolution
Evolution by NS is a genetic and ecological
process
– Ecology produces selection
– Genetics provides the material that is transmitted
across generations
For humans, ‘ecology’ includes culture and the
organisms we interact with
What imprint does this have on the genome of
each species? 8
Human infants depend on milk…adults?
•Humans digest
milk using the
lactase enzyme
•Humans get many
useful milk-based
products
Lactose
Lactase
Lactase production normally declines in adulthood
•Exception: people of north European origin
•Decline in lactase yields the “lactose intolerant” suite of symptoms
Note that “WT” is to be lactose intolerant as an adult!
Glucose + Galactose
9
Unique culture and ecology of humans: cattle
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Lactase Persistence in Human Populations
In many humans of European origin, lactase
production persists through adulthood
Allows digestion of milk
Is this a chance effect, or due to selection?
Has this had any effect on the cows?
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Evolution in European Cattle Farming Cultures
•Observation:
– In European populations, changes in the lactase gene
strongly correlated with the ability to digest lactose
as an adult
Hypotheses:
– The substitutions are the causal variants
They were favored by natural selection
12
Predictions
If substitutions in the lactase gene cause lactase persistence,
then we would predict:
Other human populations with lactase persistence should have the
same substitutions, or changes with similar consequences.
If dairy agriculture imposed evolution by natural selection on
substitutions that cause lactase persistence,
then we would predict:
Other human populations practicing dairy agriculture should have
lactase persistent phenotypes.
We should see genetic evidence of past selection at the lactase gene.
substitution/nucleotide
In genetics, a type of mutation due to replacement of one nucleotide in a DNA sequence by another nucleotide or replacement of one
amino acid in a protein by another amino acid.
Substitution is a type of mutation where one base pair is replaced by a different base pair. The term also refers to the replacement of
one amino acid in a protein with a different amino acid.
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