ch. 22/23 warm-up 1.what is the evidence for evolution?
TRANSCRIPT
![Page 1: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/1.jpg)
CH. 22/23 WARM-UP
1. What is the evidence for evolution?
![Page 2: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/2.jpg)
CHAPTER 23
THE EVOLUTION OF POPULATIONS
![Page 3: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/3.jpg)
WHAT YOU MUST KNOW:
• How mutation and sexual reproduction each produce genetic variation.
• The conditions for Hardy-Weinberg equilibrium.
![Page 4: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/4.jpg)
SMALLEST UNIT OF EVOLUTION
Microevolution: change in the allele frequencies of a population over generations
![Page 5: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/5.jpg)
• Darwin did not know how organisms passed traits to offspring
• 1866 - Mendel published his paper on genetics
• Mendelian genetics supports Darwin’s theory Evolution is based on genetic variation
![Page 6: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/6.jpg)
SOURCES OF GENETIC VARIATION
• Point mutations: changes in one base (eg. sickle cell)
• Chromosomal mutations: delete, duplicate, disrupt, rearrange usually harmful
• Sexual recombination: contributes to most of genetic variation in a population1.Crossing Over (Meiosis – Prophase I)2.Independent Assortment of Chromosomes
(during meiosis)3.Random Fertilization (sperm + egg)
![Page 7: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/7.jpg)
Population genetics: study of how populations change genetically over time
Population: group of individuals that live in the same area and interbreed, producing fertile offspring
![Page 8: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/8.jpg)
• Gene pool: all of the alleles for all genes in all the members of the population• Diploid species: 2 alleles for a gene
(homozygous/heterozygous)• Fixed allele: all members of a population
only have 1 allele for a particular trait• The more fixed alleles a population has,
the LOWER the species’ diversity
![Page 9: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/9.jpg)
HARDY-WEINBERG THEORM
Hardy-Weinberg Theorm: The allele and genotype frequencies of a population will remain constant from generation to generation
…UNLESS they are acted upon by forces other than Mendelian segregation and recombination of alleles
Equilibrium = allele and genotype frequencies remain constant
![Page 10: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/10.jpg)
CONDITIONS FOR HARDY-WEINBERG EQUILIBRIUM
1. No mutations.2. Random mating.3. No natural selection.4. Extremely large population size.5. No gene flow.
If at least one of these conditions is NOTNOT met, then the population is EVOLVINGEVOLVING!
![Page 11: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/11.jpg)
CAUSES OF EVOLUTION
![Page 12: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/12.jpg)
CONDITIONS FOR HARDY-WEINBERG EQUILIBRIUM
1. No mutations.2. Random mating.3. No natural selection.4. Extremely large population size.5. No gene flow.
If at least one of these conditions is NOTNOT met, then the population is EVOLVINGEVOLVING!
![Page 13: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/13.jpg)
Minor Causes of Evolution:Minor Causes of Evolution:#1 - Mutations
• Rare, very small changes in allele frequencies
#2 - Nonrandom mating• Affect genotypes, but not allele
frequencies
Major Causes of EvolutionMajor Causes of Evolution:• Natural selection, genetic drift, gene flow
(#3-5)
![Page 14: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/14.jpg)
MAJOR CAUSES OF EVOLUTION
#3 – Natural Selection#3 – Natural Selection• Individuals with variations better suited
to environment pass more alleles to next generation
![Page 15: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/15.jpg)
MAJOR CAUSES OF EVOLUTION
#4 – Genetic Drift#4 – Genetic Drift• Small populations have greater chance of fluctuations in
allele frequencies from one generation to another• Examples:
• Founder Effect• Bottleneck Effect
![Page 16: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/16.jpg)
Genetic DriftGenetic Drift
![Page 17: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/17.jpg)
FOUNDER EFFECT
• A few individuals isolated from larger population• Certain alleles under/over represented
Polydactyly in Amish population
![Page 18: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/18.jpg)
BOTTLENECK EFFECT
• Sudden change in environment drastically reduces population size
Northern elephant seals hunted nearly to extinction in
California
![Page 19: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/19.jpg)
MAJOR CAUSES OF EVOLUTION
#5 – Gene Flow#5 – Gene Flow• Movement of fertile
individuals between populations
• Gain/lose alleles• Reduce genetic
differences between populations
![Page 20: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/20.jpg)
HOW DOES NATURAL SELECTION BRING ABOUT ADAPTIVE EVOLUTION?
![Page 21: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/21.jpg)
Natural selection can alter frequency distribution of heritable traits in 3 ways:
1.Directional selection2.Disruptive (diversifying) selection3.Stabilizing selection
![Page 22: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/22.jpg)
Directional Selection: eg. larger black bears survive extreme cold better than small ones
Disruptive Selection: eg. small beaks for small seeds; large beaks for large seeds
Stabilizing Selection: eg. narrow range of human birth weight
![Page 23: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/23.jpg)
SEXUAL SELECTION
• Form of natural selection – certain individuals more likely to obtain mates
• Sexual dimorphism: difference between 2 sexes• Size, color, ornamentation, behavior
![Page 24: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/24.jpg)
SEXUAL SELECTION
• IntrasexualIntrasexual – selection within same sex (eg. M compete with other M)
• IntersexualIntersexual – mate choice (eg. F choose showy M)
![Page 25: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/25.jpg)
PRESERVING GENETIC VARIATION
• DiploidyDiploidy: hide recessive alleles that are less favorable
• Heterozygote advantageHeterozygote advantage: greater fitness than homozygotes• eg. Sickle cell disease
![Page 26: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/26.jpg)
NATURAL SELECTION CANNOT FASHION PERFECT ORGANISMS.
1. Selection can act only on existing variations.
2. Evolution is limited by historical constraints.
3. Adaptations are often compromises.
4. Chance, natural selection, and the environment interact.
![Page 27: CH. 22/23 WARM-UP 1.What is the evidence for evolution?](https://reader035.vdocuments.mx/reader035/viewer/2022062720/56649f0e5503460f94c22c2b/html5/thumbnails/27.jpg)
SAMPLE PROBLEM
Define the following examples as directional, disruptive, or stabilizing selection:
a) Tiger cubs usually weigh 2-3 lbs. at birthb) Butterflies in 2 different colors each
represent a species distasteful to birdsc) Brightly colored birds mate more
frequently than drab birds of same species
d) Fossil evidence of horse size increasing over time