![Page 1: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/1.jpg)
Chapter 16
Evolution of Populations
![Page 2: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/2.jpg)
Ch. 16 Evolution of Populations
• 16–1Genes and VariationA. How Common is Genetic Variation?
– Most genes have two forms.– Many genes have multiple alleles.– Many traits are polygenic.
B. Variation and Gene Pools• Gene pools have frequency of certain traits.• This frequency changes over time.
– This increases or decreases the variation in the population
![Page 3: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/3.jpg)
Ch. 16 Evolution of Populations
C. Sources of Genetic Variation1. Mutations
• http://www.koshlandsciencemuseum.org/exhibitdna/crops04activity.jsp
2. Gene Shuffling• Independent assortment of
chromosomes during meiosis.
D. Single-Gene and Polygenic Traits– 2 phenotypes vs. many phenotypes
Click here to go to next outline
![Page 4: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/4.jpg)
Ch. 16 Evolution of Populations
Fre
qu
en
cy
O
f p
he
no
typ
e
Phenotype (height)
Polygenic
Traits will make a bell curve when graphed
Click here to return to outline-
![Page 5: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/5.jpg)
Ch. 16 Evolution of Populations
• A single gene trait makes a bar graph with two phenotypes
Click here to return to outline
![Page 6: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/6.jpg)
Ch. 16 Evolution of Populations
• 16–2 Evolution as Genetic ChangeA. Natural Selection on Single-Gene
Traits– Natural selection on single-gene
traits can lead to changes in allele frequencies and thus to evolution.
• Run this simulation of the perrered moth evolution.
http://www.biologycorner.com/worksheets/pepperedmoth.html
![Page 7: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/7.jpg)
Ch. 16 Evolution of Populations
B. Natural Selection on Polygenic Traits
Natural selection can affect the distributions of phenotypes in any of three ways 1. Directional Selection
2. Stabilizing Selection
3. Disruptive Selection
![Page 8: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/8.jpg)
Ch. 16 Evolution of Populations
– C. Genetic Drift
Sample of Original Population
Founding Population A
Founding Population B
Descendants
Click here to continue with outline
![Page 9: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/9.jpg)
Ch. 16 Evolution of Populations
• Click to return to outline
Low mortality, high fitness
High mortality, low fitness
Directional Selection
![Page 10: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/10.jpg)
Ch. 16 Evolution of Populations
• Click here to return to outline
Selection against both
extremes keep curve narrow and in same
place.
Low mortality, high fitness
High mortality, low fitness
Stabilizing Selection
Selection against both
extremes keep curve narrow and in same
place.
Low mortality, high fitness
High mortality, low fitness
Stabilizing Selection
![Page 11: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/11.jpg)
Ch. 16 Evolution of Populations
• Click here to continue with outline
Disruptive Selection
Largest and smallest seeds become more common.
Beak Size
Population splits into two subgroups specializing in different seeds.
Beak Size
Low mortality, high fitness
High mortality, low fitness
Disruptive Selection
Largest and smallest seeds become more common.
Beak Size
Population splits into two subgroups specializing in different seeds.
Beak Size
Low mortality, high fitness
High mortality, low fitness
![Page 12: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/12.jpg)
Ch. 16 Evolution of Populations
D. Evolution Versus Genetic Equilibrium
The Hardy-Weinberg principle states that allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change.
In other words, as long as everything stays the same, evolution will not happen.
![Page 13: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/13.jpg)
Ch. 16 Evolution of Populations
Genetic Equilibrium Five conditions are required to maintain
genetic equilibrium from generation to generation
1. Random Mating2. Large Population3. No Movement Into or Out of the
Population4. No Mutations5. No Natural Selection
![Page 14: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/14.jpg)
Ch. 16 Evolution of Populations
16–3 The Process of Speciation-how do species evolve?A. Isolating Mechanisms-ALL types of
isolation result in Reproductive Isolation.1.Behavioral Isolation-have differences in courtship
rituals
2.Geographic Isolation-are separated by geographic barriers such as rivers, mountains, or bodies of water.
3.Temporal Isolation-reproduce at different times.
![Page 15: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/15.jpg)
Ch. 16 Evolution of Populations
B. Testing Natural Selection in Nature
Examples of Evolution observed in Nature• Peppered Moth• Antibiotic resistance in bacteria• Human adults who can digest milk• Gypsy Moth• Insects able to survive insecticides• Plants able to survive herbicides• Darwin’s finches-see next page• Sickle cell trait in humans
![Page 16: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/16.jpg)
Ch. 16 Evolution of Populations
C. Speciation in Darwin’s Finches1. Founders Arrive-birds arrive from S. America
perhaps blown there by a storm2. Separation of Populations-The small population is
separated on different islands.3. Changes in the Gene Pool-Natural variation due to
mutation occurs4. Reproductive Isolation-Birds are isolated by
behavior and geography5. Ecological Competition-Each island has specific
foods in limited amounts6.Continued Evolution-all of these drive changes in
the population (evolution) which is documented even today
![Page 17: Chapter 16 Evolution of Populations. Ch. 16 Evolution of Populations 16–1Genes and Variation A.How Common is Genetic Variation? –Most genes have two forms](https://reader036.vdocuments.us/reader036/viewer/2022062515/56649f4e5503460f94c6ec6f/html5/thumbnails/17.jpg)
Ch. 16 Evolution of PopulationsD. Studying Evolution Since Darwin• Advances in genetics, molecular biology,
ecology, physics and chemistry increase the evidence that species change over time and continue to change.
E. Limitations on Research• Evidence of change exists. But no one has yet
witnessed the formation of a brand new species.• Many new discoveries have led to new
hypotheses that refine and expand Darwin's original ideas. Even Darwin has evolved.
• There are still many unanswered questions.