Transcript Chapter 16 - Ms. Lee`s Classes @ JICHS

Chapter 16:
Population Genetics and Speciation
Chapter 16.1
Genetic Equilibrium
Evolution by Natural Selection
• widely accepted by end 1800s
• Further genetics research supported
it
What’s population genetics?
• Studying evolution of genes in a
population
• Type of Microevolution
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What’s an allele?
What’s a species?
Same genotypes?
Interbreed?
Can an individual evolve?
NO!!!!!
What are causes of VARIATION?
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Environmental factors
Heredity
Mutations
Recombination
Random pairing of gametes
Complex characters
GENE POOL...
• ALL ALLELES IN
POPULATION
• Allele Frequency
Example:
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20 lions in population
½ are heterozygous
¼ are hom dom
¼ are hom rec
Freq of A?
Freq of a?
How’s allele frequency
different from
phenotype frequency?
Hardy-Weinberg Equilibrium
• Genotype frequencies usually stay
~same across generations UNLESS
acted on by outside influences...
• ?????
• Important b/c...
• Tells us what forces may disrupt
genetic equilibrium & allow for
evolution to take place
How it can
change the
population:
5 Assumptions of
Hardy-Weinberg Principle:
1. No net mutations; alleles remain
same.
2. No immigration or emigration
3. Large population size
4. Random mating
5. No selection occurring
5 Factors that can lead to
Evolution:
1.
2.
3.
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5.
Genetic drift
Gene flow
Mutation
Sexual selection
Natural selection
REVIEW...
1. What are 3 causes of genetic
variation in a population?
2. What’s a GENE POOL?
3. How do you calculate genotype &
phenotype frequency?
4. What are the assumptions of the HW principle?
5. How does the pairing of gametes
produce genotypic variation?
Allele Frequency Practice
Opener, Wednesday Jan. 6th
Start a new opener sheet &
answer in complete sentences.
Some tigers have a recessive allele that
causes an absence of fur pigment in
homozygous individuals (albino tigers).
• Do you think the white phenotype in tigers
is favored by natural selection?
• Why or why not?
• What does this mean for the occurrence of
the allele in future generations (more,
less)?
Earth Force Update
• TEAM LEADERS—
– Check in with team
members…everyone’s assignment
turned in?
• Those who haven’t done anything yet—
– Contact rental agencies
» Ask how many beachfront properties
they manage
» Tell them about our project
» Ask if they’d use stickers/magnets if we
gave them to them
» Ask if they’d use flyers if we gave them
to them
– Contact Stacey
» Any luck with $ for lightbulbs or signs?
• Class vote
– Design & text for flyer, magnet/sticker
Project Stuff
• Team Leaders—
Wed., Jan. 6th!
List the 5 assumptions of
Hardy-Weinberg Equilibrium?
• ANY EXCEPTIONS 
• CHANGE IN ALLELE FREQ 
• EVOLUTION OF POPULATION OVER
GENERATIONS
16-2:
Disruption of
Genetic Equilibrium
Looking at those H-W
assumptions…continuing on
your chart.
1. Mutations
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Mutagens increase mutation rates
Radiation, chemicals
New alleles
-/0/+
2. Gene Flow
• Change in population size...how?
• Immigration, emigration
– Migration, seed dispersal
• Male apes moving to new
troops...gene flow?
3. Genetic Drift
• Allele freq changes due to random
event/chance
• Small pop  bigger effects
4. Nonrandom Mating
• Many species don’t
mate randomly!
• Geography, similar
traits (assortative
mating), sexual
selection
• SURVIVE &
REPRODUCE!
5. Natural Selection
• Ongoing in nature
• SURVIVE &
REPRODUCE!
• 3 patterns/modes
Campbell CD
• Activity 13D
REVIEW!
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How can mutation lead to evolution?
What’s gene flow?
How’s it different from genetic drift?
Why does genetic drift affect small
populations more dramatically?
Stabilizing selection? Example?
Disruptive?
Directional?
Example OTHER THAN A PEACOCK/BIRD for
sexual selection?
Practice!
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Beads
Rat Islands
Or
Natural Selection/Camouflage
Opener, Thurs. Jan 7th
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Use the following terms in a
sentence to summarize what you
learned yesterday & LINK it to last
night’s homework:
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Genetic equilibrium
Gene pool
Speciation
Opener, Thursday Jan. 7th
Some tigers have a recessive allele
that causes an absence of fur
pigment in homozygous
individuals (albino tigers).
 Do you think the white
phenotype in tigers is favored by
natural selection?
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Why or why not?
Will it be selected “for” or “against”?
What does this mean for the
occurrence of the allele in future
generations (more, less)?
16-3: Speciation
How many species are on Earth?
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BioBucks! Estimate w/reference…
Reproductive Isolation:
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Can be caused by...
1.
2.
3.
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Is the final stage of ...
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1. Behavioral Isolation
• Courtship/mating
behavior
• Prevents reproduction
between populations
• (Leads to evolution of
new species)
• Examples: bird songs,
firefly lights
2. Geographical Isolation
• Physical barriers divide a
population into 2 or more
groups
• Prevents repro. b/w pops.
• (Leads to evolution of new
species)
• Examples: 10,000 yrs ago—
Colorado River…squirrels @ N.
& S. rim of Grand Canyon
• Mountains—salamanders
• Islands—finches, tortoises!
3. Temporal Isolation
• TIMING of reproductive or
courtship events
• prevents repro. b/w pops.
• (Leads to evolution of new
species)
• Examples: flowers w/ diff.
bloom times
• Clams—different
spawning times
What’s speciation?
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Common ancestor
Deviations
Similar ------- very different
How can some be similar and some
so different?
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Time!
How do scientists determine if
2 organisms are the same species?
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Morphology, anatomy
Molecular evidence
INTERBREED & PRODUCE
FULLY FERTILE OFFSPRING
http://evolution.berkeley.edu/evosite/evo101/VSpeciation.shtml
Isolation, leads to
speciation
Reproductive
or Geographic?
Example:
A physical barrier divides
the population into two or
more groups that can no
longer reproduce with
each other.
Allopatric:
Differences in courtship or
mating behaviors prevent
reproduction between
populations.
Prezygotic:
Postzygotic:
Sympatric:
How long does this take?
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Depends on the species &
conditions!
Gradualism:
Punctuated equilibrium:
Test Tomorrow…
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Review Ch 17 also!
Ch 14, 15, 16
Let’s go over your quiz so you can
STUDY it
Test Corrections available …
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Friday, Monday, Tuesday only.
Must have HW completed!
Chapter 16 Activity: Data Analysis,
Frequencies, & Natural Selection
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Identifying patterns in data by
studying graphs and charts is
important in making future
predictions and hypotheses.
Population Genetics
Swordtails are small freshwater
fish. One section of the tail of the
male fish is elongated and has a
specific color pattern of two black
lines running the outside length of
the section, with yellow in the
middle. Scientists conducted an 
experiment to determine which
component of the color pattern
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may be most attractive to the
female swordtail during mating. 
The females were exposed to three
different stimuli: a normal male 
fish tail, an all-black male fish tail,
and an all-yellow male f ish tale. 
The response of the females to
each stimulus was recorded. The
graph below shows the results of
the research.
Groups of 3
Read
Analyze Graph
Answer questions AS A GROUP
Write on your own paper
Concept Map:
http://my.hrw.com/sh2/sh07_10/student
/flash/concept_maps/00171.htm
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Bill nye, jeff corwin
AQUATERRA ACTIVITY!
PAIR-SHARE
• Sandstone, siltstone
• Die, water, sink, more aquatic
fossils
• Erosion (mts, hills, river sediment,
etc.)...Appalachian used to be
bigger than Himalayan mts.
• No plate pushing up App. Now,
landmass far gone...