Population Genetics

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Population Genetics I. Basic Principles A.
Definitions B. Basic computations C.
Hardy-Weinberg Equilibrium D. Utility E.
Violating each Assumption 1. Mutation 2.
Migration 3. Non-random mating 4. Drift 5. NS

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5. NS a. Components of Fitness -
probability of survival to reproductive age -
number of offspring - probability that
offspring survive to reproduce
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5. NS a. Components of Fitness -
probability of survival to reproductive age -
number of offspring - probability that
offspring survive to reproduce Can't maximize
all three components at the same time there are
trade-offs that ultimately correlate with
important ecological and populational
descriptors.
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5. NS a. Components of Fitness -
probability of survival to reproductive age -
number of offspring - probability that
offspring survive to reproduce b.
Relationships with Energy Budgets
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5. NS a. Components of Fitness b.
Relationships with Energy Budgets
GROWTH
METABOLISM
REPRODUCTION
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5. NS a. Components of Fitness b.
Relationships with Energy Budgets
Maximize probability of survival
Maximize reproduction
GROWTH
METABOLISM
GROWTH
REPRODUCTION
METABOLISM
REPRODUCTION
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5. NS a. Components of Fitness b.
Relationships with Energy Budgets
Trade-offs within reproduction
METABOLISM
REPRODUCTION
REPRODUCTION
METABOLISM
A few large, high prob of survival
Lots of small, low prob of survival
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5. NS a. Components of Fitness b.
Relationships with Energy Budgets c.
Modeling Selection
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c. Modeling Selection Selection for a Dominant
Allele
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c. Modeling Selection Selection for a Dominant
Allele
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c. Modeling Selection Selection for a Dominant
Allele
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c. Modeling Selection Selection for a Dominant
Allele
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c. Modeling Selection Selection for a Dominant
Allele
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c. Modeling Selection Selection for a Dominant
Allele
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c. Modeling Selection Selection for a Dominant
Allele
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c. Modeling Selection Selection for a Dominant
Allele
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c. Modeling Selection Selection for a Dominant
Allele
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Evolution and Population Genetics I. The Modern
Synthesis A. Darwin's Primary Contributions
B. The Contribution of Genetics C. The
Contribution of Population Genetics D. The
Modern Synthesis Sources of Variation Agents
of Change Mutation N.S. Recombination Drif
t - crossing over Migration - independent
assortment Mutation Non-random Mating
VARIATION
So, if NO AGENTS are acting on a population, then
it will be in equilibrium and WON'T change.
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Evolution and Population Genetics I. The Modern
Synthesis A. Darwin's Primary Contributions
B. The Contribution of Genetics C. The
Contribution of Population Genetics II. Beyond
the Synthesis
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Evolution and Population Genetics I. The Modern
Synthesis A. Darwin's Primary Contributions
B. The Contribution of Genetics C. The
Contribution of Population Genetics II. Beyond
the Synthesis A. Punctuated Equilibrium
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
1. Consider a large, well-adapted population
VARIATION
TIME
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
1. Consider a large, well-adapted
population Effects of Selection and Drift are
small - little change over time
VARIATION
TIME
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
2. There are always small sub-populations
"budding off" along the periphery of a species
range...
VARIATION
TIME
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
2. Most will go extinct, but some may survive...
VARIATION
X
X
X
TIME
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
2. These surviving populations will initially be
small, and in a new environment...so the effects
of Selection and Drift should be strong...
VARIATION
X
X
X
TIME
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
3. These populations will change rapidly in
response...
VARIATION
X
X
X
TIME
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
3. These populations will change rapidly in
response... and as they adapt (in response to
selection), their populations should increase in
size (because of increasing reproductive success,
by definition).
VARIATION
X
X
X
TIME
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
3. As population increases in size, effects of
drift decline... and as a population becomes
better adapted, the effects of selection
decline... so the rate of evolutionary change
declines...
VARIATION
X
X
X
TIME
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
4. And we have large, well-adapted populations
that will remain static as long as the
environment is stable...
VARIATION
X
X
X
TIME
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
5. Since small, short-lived populations are less
likely to leave a fossil, the fossil record can
appear 'discontinuous' or 'imperfect'
VARIATION
X
X
X
TIME
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
5. Large pop's may leave a fossil....
VARIATION
X
X
X
TIME
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
5. Small, short-lived populations probably
won't...
VARIATION
X
X
X
TIME
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
6. So, the discontinuity in the fossil record is
an expected result of our modern understanding of
how evolution and speciation occur...
VARIATION
X
X
X
TIME
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- 1972 - Eldridge and Gould - Punctuated
Equilibrium
6. both in time (as we see), and in SPACE (as
changing populations are probably NOT in same
place as ancestral species).
VARIATION
X
X
X
TIME
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
1. Core Processes - Basic biological processes
are CONSERVED, and the enzymes that perform them
are CONSERVED - Many enzymes are more than 50
similar in AA sequence in E. coli and H. sapiens,
though separated by 2 billion years of
divergence. - Of 548 metabolic enzymes in E.
coli, 50 are present in ALL LIFE, and only 13
are unique to bacteria.
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
1. Core Processes - Basic biological processes
are CONSERVED, and the enzymes that perform them
are CONSERVED - Many enzymes are more than 50
similar in AA sequence in E. coli and H. sapiens,
though separated by 2 billion years of
divergence. - Of 548 metabolic enzymes in E.
coli, 50 are present in ALL LIFE, and only 13
are unique to bacteria. - So the variation and
diversity of life is NOT due to changes in
metabolic or structural genes... we are all built
out of the same stuff, that works the same way at
a cellular level.
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
- Variation is largely due to HOW these
processes are REGULATED... 300 cell types in
humans, all descended from the zygote all
genetically the same. - Best (and most
fundamental) examples are HOX genes. These are
'homeotic genes' that produce a variety of
transcription factors. The production and
localization of these transcription factors are
CRITICAL in determining the developmental
compartments' of bilaterally symmetrical
animals.
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
- Effects can be profound
- 'Master Switches' that initiate downstream
cascades that can be very different... like
compound or vertebrate eyes.
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
2. Exploratory Behavior - environmental cues
affect cell activity - production of growth
factors
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
2. Exploratory Behavior - environmental cues
affect cell activity - production of growth
factors - hypoxia - stimulates cell to produce
endothelial growth factor
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
2. Exploratory Behavior - environmental cues
affect cell activity - production of growth
factors - hypoxia - stimulates cell to produce
endothelial growth factor - neighboring vascular
tissue grows towards the source of growth
factor
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
2. Exploratory Behavior - environmental cues
affect cell activity - production of growth
factors - hypoxia - stimulates cell to produce
endothelial growth factor - neighboring vascular
tissue grows towards the source of growth factor
- and BINGO... now you have vascular tissue and
hypoxia is corrected
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
V. Physiology and Evolution
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
V. Physiology and Evolution - stress can
reveal new phenotypes - "norm of reaction"
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
V. Physiology and Evolution - stress can
reveal new phenotypes - "norm of reaction" -
(cloned plants raised in different environments
will look different, as a result of different
physiological responses and gene action.)
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
V. Physiology and Evolution - stress can
reveal new phenotypes - "norm of reaction" -
(cloned plants raised in different environments
will look different, as a result of different
physiological responses and gene action.) -
Initially, this response is phenotypic and
probably suboptimal in integration.... enzymes
may be off their optima, for example. However,
mutations that stabilize this phenotype (create
it with greater integration) would be selected
for.
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
V. Physiology and Evolution - stress can
reveal new phenotypes - "norm of reaction" -
(cloned plants raised in different environments
will look different, as a result of different
physiological responses and gene action.) -
Initially, this response is phenotypic and
probably suboptimal in integration. However,
mutations that stabilize this phenotype (create
it with greater integration) would be selected
for. - So the phenotype might not change, but
it shifts from a physiological stress response to
a genetically encoded norm. Subsequent stress
expresses new variation...
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II. Beyond the Synthesis A. Punctuated
Equilibrium B. Evo-Devo the influence of
developmental programs
Sources of Variation
Agents of Change
Selection Drift Mutation Migration Non-Random
Mating
Mutation Recombination
PHYSIOLOGY DEVELOPMENT
VARIATION