Chapter 16: Chapter 16: Population Genetics and SpeciationPopulation Genetics and Speciation

Chapter 16.1Chapter 16.1

Genetic EquilibriumGenetic Equilibrium

Evolution by Natural SelectionEvolution by Natural Selection

• widely accepted by end 1800swidely accepted by end 1800s

• Further genetics research supported Further genetics research supported itit

What’s What’s population geneticspopulation genetics??

• Studying evolution of genes in a Studying evolution of genes in a populationpopulation

• Type ofType of Microevolution Microevolution

• What’s an allele?What’s an allele?• What’s a species?What’s a species?• Same genotypes?Same genotypes?• Interbreed?Interbreed?

Can an individual evolve?Can an individual evolve?

NO!!!!!NO!!!!!

What are causes of VARIATION?What are causes of VARIATION?

• Environmental factorsEnvironmental factors

• HeredityHeredity

• MutationsMutations

• RecombinationRecombination

• Random pairing of gametesRandom pairing of gametes

• Complex charactersComplex characters

GENE POOLGENE POOL......• ALL ALLELES IN ALL ALLELES IN

POPULATIONPOPULATION

• Allele FrequencyAllele Frequency Example:Example:• 20 lions in population20 lions in population• ½ are heterozygous½ are heterozygous• ¼ are hom dom¼ are hom dom• ¼ are hom rec¼ are hom rec• Freq of A?Freq of A?• Freq of a?Freq of a?

How’s How’s alleleallele frequency frequency different from different from phenotypephenotype frequency? frequency?

Hardy-Weinberg EquilibriumHardy-Weinberg Equilibrium• Genotype frequencies usually stay Genotype frequencies usually stay

~same across generations UNLESS ~same across generations UNLESS acted on by outside influences...acted on by outside influences...

• ??????????

• Important b/c...Important b/c...• Tells us what forces may Tells us what forces may disruptdisrupt

genetic equilibrium & genetic equilibrium & allow for allow for evolution to take placeevolution to take place

How it can How it can change the change the population:population:

5 Assumptions of 5 Assumptions of Hardy-Weinberg Principle:Hardy-Weinberg Principle:1.1. No net mutations; alleles remain No net mutations; alleles remain

same.same.

2.2. No immigration or emigrationNo immigration or emigration

3.3. Large population sizeLarge population size

4.4. Random matingRandom mating

5.5. No selection occurring No selection occurring

5 Factors that can lead to 5 Factors that can lead to Evolution:Evolution:

1.1. Genetic driftGenetic drift

2.2. Gene flowGene flow

3.3. MutationMutation

4.4. Sexual selectionSexual selection

5.5. Natural selectionNatural selection

REVIEW...REVIEW...

1.1. What are 3 causes of genetic What are 3 causes of genetic variation in a population?variation in a population?

2.2. What’s a GENE POOL?What’s a GENE POOL?3.3. How do you calculate genotype & How do you calculate genotype &

phenotype frequency?phenotype frequency?4.4. What are the assumptions of the H-What are the assumptions of the H-

W principle?W principle?5.5. How does the pairing of gametes How does the pairing of gametes

produce genotypic variation?produce genotypic variation?

Allele Frequency PracticeAllele Frequency PracticeOpener, Wednesday April 24thOpener, Wednesday April 24th

There are 100 Heffalumps in the population. There are 100 Heffalumps in the population. 80 have an extra-long snout (homozygous 80 have an extra-long snout (homozygous dominant). dominant). 15 have a medium-sized snout 15 have a medium-sized snout (heterozygous). (heterozygous). 5 have a short snout (homozygous 5 have a short snout (homozygous recessive). recessive). Calculate the allele frequency for both Calculate the allele frequency for both alleles.alleles.

Some tigers have a recessive allele that Some tigers have a recessive allele that causes an absence of fur pigment in causes an absence of fur pigment in homozygous individuals (albino tigers).homozygous individuals (albino tigers).

• Do you think the white phenotype in tigers Do you think the white phenotype in tigers is favored by natural selection?is favored by natural selection?• Why or why not?Why or why not?

• What does this mean for the occurrence of What does this mean for the occurrence of the allele in future generations (more, the allele in future generations (more, less)?less)?

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

• Mutagens increase mutation rates

• Radiation, chemicals

• New alleles

• - / 0 / + effects

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!

• 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!

• Beads

• Rat Islands

• Or

• Natural Selection/Camouflage

Opener, Thurs. Jan 7th

Use the following terms in a sentence to summarize what you learned yesterday & LINK it to last night’s homework:

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? 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?How many species are on Earth?

BioBucks! Estimate w/reference…

http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001127

Reproductive Isolation:

Can be caused by... 1. 2. 3.

Is the final stage of ...

1. Behavioral Isolation1. Behavioral Isolation• Courtship/mating Courtship/mating

behaviorbehavior

• Prevents reproduction Prevents reproduction between populationsbetween populations

• (Leads to evolution of (Leads to evolution of new species)new species)

• Examples: bird songs, Examples: bird songs, firefly lightsfirefly lights

2. Geographical Isolation2. Geographical Isolation• Physical barriers divide a Physical barriers divide a

population into 2 or more population into 2 or more groupsgroups

• Prevents repro. b/w pops.Prevents repro. b/w pops.• (Leads to evolution of new (Leads to evolution of new

species)species)• Examples: 10,000 yrs ago—Examples: 10,000 yrs ago—

Colorado River…squirrels @ N. Colorado River…squirrels @ N. & S. rim of Grand Canyon& S. rim of Grand Canyon

• Mountains—salamandersMountains—salamanders• Islands—finches, tortoises! Islands—finches, tortoises!

3. Temporal Isolation3. Temporal Isolation• TIMING of reproductive or TIMING of reproductive or

courtship events courtship events • prevents repro. b/w pops.prevents repro. b/w pops.• (Leads to evolution of new (Leads to evolution of new

species)species)• Examples: flowers w/ diff. Examples: flowers w/ diff.

bloom timesbloom times• Clams—different Clams—different

spawning timesspawning times

What’s speciation?What’s speciation?

Common ancestor Deviations Similar ------- very different How can some be similar and some

so different? Time!

How do scientists determine if How do scientists determine if 2 organisms are the same species?2 organisms are the same species?

Morphology, anatomy Molecular evidence

INTERBREED & PRODUCE FULLY FERTILE OFFSPRING

http://evolution.berkeley.edu/evosite/evo101/VSpeciation.shtml

Isolation, leads to speciation

Reproductive, Temporal, or Geographic?

Example:

Physical barrier divides pop into 2 or more groups that can no longer reproduce with each other

Allopatric speciation--

Differences in courtship/mating behaviors prevent reproduction between pops.

Prezygotic:

Postzygotic:

How long does this take?How long does this take? Depends on the species &

conditions!

Gradualism: Punctuated equilibrium:

Test Tomorrow…

Review Ch 17 also!Review Ch 17 also! Ch 14, 15, 16Ch 14, 15, 16 Let’s go over your quiz so you can

STUDY it Test Corrections available …

Friday, Monday, Tuesday only. Must have HW completed!

Chapter 16 Activity: Data Analysis, Frequencies, & Natural Selection

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 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 Bill nye, jeff corwin

AQUATERRA ACTIVITY!

PAIR-SHAREPAIR-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...