Population Genetics and Speciation

1
Chapter 16

• Population Genetics and Speciation

2
Chapter 16.1

• Genetic Equilibrium

3
Evolution by Natural Selection

• widely accepted by end 1800s
• Further genetics research supported it

4
Whats population genetics?

• Studying evolution of genes in a population
• Type of Microevolution
• Whats an allele?
• Whats a species?
• Same genotypes?
• Interbreed?

5
Can an individual evolve?

• NO!!!!!

6
What are causes of VARIATION?

• Environmental factors
• Heredity
• Mutations
• Recombination
• Random pairing of gametes
• Complex characters

7
(No Transcript)
8
GENE POOL...

• ALL ALLELES IN POPULATION
• Allele Frequency Example
• 20 lions in population
• ½ are heterozygous
• ¼ are hom dom
• ¼ are hom rec
• Freq of A?
• Freq of a?

9
Hows allele frequency different from phenotype
frequency?
10
(No Transcript)
11
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

12
How it can change the population
13
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

14
(No Transcript)
15
5 Factors that can lead to Evolution

1. Genetic drift
2. Gene flow
3. Mutation
4. Sexual selection
5. Natural selection

16
REVIEW...

1. What are 3 causes of genetic variation in a
   population?
2. Whats a GENE POOL?
3. How do you calculate genotype phenotype
   frequency?
4. What are the assumptions of the H-W principle?
5. How does the pairing of gametes produce genotypic
   variation?

17
Allele Frequency Practice
Opener, Wednesday April 24th
There are 100 Heffalumps in the population. 80
have an extra-long snout (homozygous dominant).
15 have a medium-sized snout (heterozygous). 5
have a short snout (homozygous recessive).
Calculate the allele frequency for both alleles.
18

• 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)?

19
List the 5 assumptions of Hardy-Weinberg
Equilibrium

• ANY EXCEPTIONS ?
• CHANGE IN ALLELE FREQ ?
• EVOLUTION OF POPULATION OVER GENERATIONS

20
16-2 Disruption of Genetic EquilibriumLooki
ng at those H-W assumptionscontinuing on your
chart.
21
1. Mutations

• Mutagens increase mutation rates
• Radiation, chemicals
• New alleles
• - / 0 / effects

22
2. Gene Flow

• Change in population size...how?
• Immigration, emigration
• Migration, seed dispersal
• Male apes moving to new troops...gene flow?

23
3. Genetic Drift

• Allele freq changes due to random event/chance
• Small pop ? bigger effects

24
4. Nonrandom Mating

• Many species dont mate randomly!
• Geography, similar traits (assortative mating),
  sexual selection
• SURVIVE REPRODUCE!

25
5. Natural Selection

• Ongoing in nature
• SURVIVE REPRODUCE!
• 3 patterns/modes

26
(No Transcript)
27
Campbell CD

• Activity 13D

28
REVIEW!

• How can mutation lead to evolution?
• Whats gene flow?
• Hows 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?

29
Practice!

• Beads
• Rat Islands
• Or
• Natural Selection/Camouflage

30
Opener, Thurs. Jan 7th

• Use the following terms in a sentence to
  summarize what you learned yesterday LINK it to
  last nights homework
• Genetic equilibrium
• Gene pool
• Speciation

31
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)?

32
16-3 Speciation
33
How many species are on Earth?

• BioBucks! Estimate w/reference

34

• http//www.plosbiology.org/article/info3Adoi2F10
  .13712Fjournal.pbio.1001127

35
Reproductive Isolation

• Can be caused by...
• 1.
• 2.
• 3.
• Is the final stage of ...

36
1. Behavioral Isolation

• Courtship/mating behavior
• Prevents reproduction between populations
• (Leads to evolution of new species)
• Examples bird songs, firefly lights

37
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 agoColorado
  Riversquirrels _at_ N. S. rim of Grand Canyon
• Mountainssalamanders
• Islandsfinches, tortoises!

38
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
• Clamsdifferent spawning times

39
Whats speciation?

• Common ancestor
• Deviations
• Similar -------? very different
• How can some be similar and some so different?
• Time!

40
How do scientists determine if 2 organisms are
the same species?

• Morphology, anatomy
• Molecular evidence
• INTERBREED PRODUCE
• FULLY FERTILE OFFSPRING

http//evolution.berkeley.edu/evosite/evo101/VSpec
iation.shtml
41
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
42
(No Transcript)
43
How long does this take?

• Depends on the species conditions!
• Gradualism Punctuated equilibrium

44
(No Transcript)
45
Test Tomorrow

• Review Ch 17 also!
• Ch 14, 15, 16
• Lets go over your quiz so you can STUDY it
• Test Corrections available
• Friday, Monday, Tuesday only.
• Must have HW completed!

46
(No Transcript)
47
(No Transcript)
48
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

49
(No Transcript)
50
(No Transcript)
51
Concept Maphttp//my.hrw.com/sh2/sh07_10/student
/flash/concept_maps/00171.htm

• Bill nye, jeff corwin

52
AQUATERRA ACTIVITY!
53
(No Transcript)
54
PAIR-SHARE
55

• 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...