Examples of Evolution by Natural Selection Microevolution vs. Macroevolution Microevolution is intraspecific evolution, evolution WITHIN a species. Microevolution.

Examples of Evolution by Natural SelectionExamples of Evolution by Natural Selection

Microevolution vs. MacroevolutionMicroevolution vs. Macroevolution

Microevolution is intraspecific evolution, Microevolution is intraspecific evolution, evolution WITHIN a species.evolution WITHIN a species.

Macroevolution is speciation. One species Macroevolution is speciation. One species evolves into a new species. evolves into a new species.

Examples of Evolution by Natural Examples of Evolution by Natural SelectionSelection

Example #1: Antibiotic ResistanceExample #1: Antibiotic Resistance This is a famous example, known by almost everyone but This is a famous example, known by almost everyone but

rarely called “evolution.” rarely called “evolution.” But it is !!! We hear “resistance develops” or resistance But it is !!! We hear “resistance develops” or resistance

emerges” etc. In fact, resistance evolves.*emerges” etc. In fact, resistance evolves.* AR is a fine example of very fast evolution ANDAR is a fine example of very fast evolution AND A fine example of one way Darwinian evolution is important A fine example of one way Darwinian evolution is important

to to youryour health and well-being. health and well-being.

*They DO NOT “become immune to the antibiotics.” *They DO NOT “become immune to the antibiotics.”

This phenomenon is NOTHING like you getting a flu shot!! This phenomenon is NOTHING like you getting a flu shot!!

Examples of Evolution by Natural Examples of Evolution by Natural SelectionSelection

Example #1: Antibiotic ResistanceExample #1: Antibiotic Resistance AR is the “poster-child” for rapid evolution.*AR is the “poster-child” for rapid evolution.* If we develop a new antibiotic this year and…If we develop a new antibiotic this year and… a resistant strain of bacteria develops in a London a resistant strain of bacteria develops in a London

hospital …hospital …• resistant strains will evolve and be in all London resistant strains will evolve and be in all London

hospitals in 6 months and…hospitals in 6 months and…• they will be observed in Hong Kong in two years, i.e. they will be observed in Hong Kong in two years, i.e.

they will have moved around the Earth in two years.they will have moved around the Earth in two years.

How does that happen?How does that happen?

*Steven Sterns, Yale U.

Examples of Evolution by Natural SelectionExamples of Evolution by Natural SelectionExample #1: Antibiotic ResistanceExample #1: Antibiotic Resistance


Example #2: Pesticide ResistanceExample #2: Pesticide Resistance Insecticides, Fungicides, Herbicides Insecticides, Fungicides, Herbicides (see first page of chapter 13)(see first page of chapter 13)

Consider DDT, the first widely usedConsider DDT, the first widely used

synthetic insecticide.synthetic insecticide.


Example #2: Pesticide ResistanceExample #2: Pesticide Resistance Insecticides, Fungicides, HerbicidesInsecticides, Fungicides, HerbicidesConsider DDT, the first widely used synthetic insecticide.Consider DDT, the first widely used synthetic insecticide. Species Resistant to InsecticidesSpecies Resistant to Insecticides

• 1948:1948: 1414• 1956:1956: 6969• 1970:1970: 224 224• 1976:1976: 364 364• 1984:1984: 447 447• 1989:1989: 504 504

Example #2: Pesticide ResistanceExample #2: Pesticide ResistanceHerbicide Resistance in 6 Species of Plants in Czech RepublicHerbicide Resistance in 6 Species of Plants in Czech Republic


Example #3: The Peppered MothExample #3: The Peppered MothBiston betulariaBiston betularia

Industrial Melanism in a Night-flying MothIndustrial Melanism in a Night-flying Moth

Fig. 18-6a1, p.288

The Peppered Moth, The Peppered Moth, Biston betulariaBiston betulariaan example of directional selectionan example of directional selection

Natural Selection in the Peppered MothNatural Selection in the Peppered Moth

H.B.D. KettlewellH.B.D. KettlewellMark and Recapture ExperimentsMark and Recapture Experiments (using caged females w/ pheromones)(using caged females w/ pheromones)

%Recaptured %Recaptured

Woodland Melanics Pepper Woodland Melanics Pepper

Urban 27.5% 13.0% Urban 27.5% 13.0%

Rural 6.3% 12.5%Rural 6.3% 12.5%

This shows a difference but does not This shows a difference but does not prove that birds CAUSED it.prove that birds CAUSED it.

Differential Predation Observations

(freshly killed moths placed on trees and watched)

# moths eaten by birds Woodland Melanics Pepper

Urban 15 43 Rural 164 26

Science is “roll up Science is “roll up your sleeves” your sleeves” process…process…

HBD doesn’t even HBD doesn’t even wear a shirt !!!wear a shirt !!!

;-);-)

Industrial melanism is seen in more than 70 species of British moths; Industrial melanism is seen in more than 70 species of British moths;

all show patterns similar to that seen in all show patterns similar to that seen in B. betulariaB. betularia..

Evolution by Natural Selection: The Peppered MothEvolution by Natural Selection: The Peppered Moth

Left: Kettelwell, 1956Left: Kettelwell, 1956 Right: Grant et.al. 1998Right: Grant et.al. 1998

Grant's comments on these maps: "The maps show a before-after comparison of the geographic distribution of melanic phenotypes in peppered Grant's comments on these maps: "The maps show a before-after comparison of the geographic distribution of melanic phenotypes in peppered moth populations in Britain based on Kettlewell's 1956 survey (left map) and that conducted 40-years later (1996) by my colleagues and me (right moth populations in Britain based on Kettlewell's 1956 survey (left map) and that conducted 40-years later (1996) by my colleagues and me (right map). The black segments of the pie charts indicate the percentage of melanics at the various locations. Clearly melanism has declined everywhere map). The black segments of the pie charts indicate the percentage of melanics at the various locations. Clearly melanism has declined everywhere it was once common." (Grant, personal communication, February 11, 2002)it was once common." (Grant, personal communication, February 11, 2002)The source publication for these maps: Grant, B. S., Cook, A. D. , Clarke, C. A., and Owen, D. F. 1998. Geographic and temporal variation in the The source publication for these maps: Grant, B. S., Cook, A. D. , Clarke, C. A., and Owen, D. F. 1998. Geographic and temporal variation in the incidence of melanism in peppered moth populations in America and Britain. Journal of Heredity 89:465-471.incidence of melanism in peppered moth populations in America and Britain. Journal of Heredity 89:465-471.


Example #4: Sickle-cell Anemia and MalariaExample #4: Sickle-cell Anemia and Malaria

Example #4: Sickle-cell Anemia and MalariaExample #4: Sickle-cell Anemia and Malaria

Okay, let’s simplify it…Okay, let’s simplify it…HbHbA A = “N” = normal= “N” = normalHbHbS S = “S” = sickle cell= “S” = sickle cell

NN = “normal”NN = “normal” Ns = “normal but carrier”Ns = “normal but carrier”

sN = “normal but carrier” sN = “normal but carrier” ss = sickle-cell anemiass = sickle-cell anemia

The Genetic Basis of Sickle Cell AnemiaThe Genetic Basis of Sickle Cell AnemiaHbA vs HbHbA vs Hbββ: Everyone has HbA (141), and Hb-non-A (146)”: Everyone has HbA (141), and Hb-non-A (146)”

HbS is a mutant form of HbA HbS is a mutant form of HbA

The Genetic Basis of Sickle Cell AnemiaThe Genetic Basis of Sickle Cell Anemia

less than 1 in 1,600

1 in 400-1,600

1 in 180-400

1 in 100-180

1 in 64-100

more than 1 in 64

Fig. 18-13b, p.293

The Distribution of the Sickle-Cell GeneThe Distribution of the Sickle-Cell Gene

Malaria: Malaria: the the PlasmodiumPlasmodium parasite parasiteSickle cell anemia is a genetic disease of the blood.Sickle cell anemia is a genetic disease of the blood.

Malaria is parasitic disease of the blood. Malaria is parasitic disease of the blood. What is the relationship between these two diseases?What is the relationship between these two diseases?

Fig. 18-13a, p.293

The Distribution of Falciparum MalariaThe Distribution of Falciparum Malaria

Geographic Distribution of Malaria vs. Sickle-cell AnemiaGeographic Distribution of Malaria vs. Sickle-cell Anemia

Sickle-Cell Trait: Sickle-Cell Trait: Heterozygote AdvantageHeterozygote Advantage

or heterosis or hybrid vigoror heterosis or hybrid vigor

Allele Allele HbHbSS causes causes sickle-cell anemia sickle-cell anemia when homozygous when homozygous

Heterozygotes Heterozygotes (NS)(NS)

are more resistant to are more resistant to malaria than malaria than homozygotes homozygotes (SS or NN) (SS or NN)

less than 1 in 1,600

1 in 400-1,600

1 in 180-400

1 in 100-180

1 in 64-100

more than 1 in 64

Malaria case

Sickle-cell trait

What Is Our View of Darwin’s Idea Today?What Is Our View of Darwin’s Idea Today?The Modern Synthesis: Darwinism Meets GeneticsThe Modern Synthesis: Darwinism Meets Genetics

To his credit, his idea has withstood the scrutiny of about 150 To his credit, his idea has withstood the scrutiny of about 150 years of scientific testing.years of scientific testing.

But a lot has happened in 150 years.But a lot has happened in 150 years.

What Is Our View of Darwin’s Idea Today?What Is Our View of Darwin’s Idea Today? Neo-Darwinism = The Modern Synthesis Neo-Darwinism = The Modern Synthesis

Neo-Darwinism Neo-Darwinism Darwin + Modern Darwin + Modern GeneticsGenetics










Neo-Darwinism Neo-Darwinism Darwin + Modern GeneticsDarwin + Modern Genetics

And also every other branch of biology that has grown since 1859 And also every other branch of biology that has grown since 1859 and contributes to our understanding of Darwin’s idea, and contributes to our understanding of Darwin’s idea, i.e. all of i.e. all of them. Especially...them. Especially...

All the “Comparatives” All the “Comparatives” Comparative Anatomy Comparative Anatomy (morphology)(morphology) Comparative Embryology Comparative Embryology (development)(development) Comparative Ethology Comparative Ethology (behavior)(behavior) Comparative Biochemistry Comparative Biochemistry (molecular biology: proteins and DNA)(molecular biology: proteins and DNA)

Biogeography Biogeography (where do they live and why?)(where do they live and why?)

Paleontology Paleontology (the fossil record)(the fossil record)

Vestigial Structures Vestigial Structures (the “scars” of evolution)(the “scars” of evolution)

Neo-Darwinism = The Modern SynthesisNeo-Darwinism = The Modern Synthesis evidence from evidence from

Comparative Anatomy (morphology)Comparative Anatomy (morphology)

HumanCat Whale Bat

Figure 13.8

Comparative AnatomyComparative Anatomyhomologous structures (vs analogous structures)homologous structures (vs analogous structures)

HumanCat Whale Bat

Figure 13.8

Comparative AnatomyComparative Anatomyhomologous structures (vs analogous structures)homologous structures (vs analogous structures)

Comparative EmbryologyComparative Embryology

Neo-Darwinism = The Modern SynthesisNeo-Darwinism = The Modern Synthesisevidence fromevidence from

Comparative Embryology (development)Comparative Embryology (development)

Post-anal

tail

Human embryoChicken embryo

Pharyngeal

pouches

Figure 13.9

Comparative Embryology

Neo-Darwinism = The Modern SynthesisNeo-Darwinism = The Modern Synthesis evidence from evidence from Molecular BiologyMolecular Biology

((Comparative Biochemistry)Comparative Biochemistry)

Neo-Darwinism = The Modern SynthesisNeo-Darwinism = The Modern Synthesis evidence from evidence from ComparativeComparative Biochemistry Biochemistry

(= comparative molecular biology)(= comparative molecular biology)

What mutation could cause isoleucine (Ile) to change to phenylalanine (Phe)?And what mutation can change Leucine (Leu) to Arginine (Arg)

Percent of selected DNA sequences

that match a chimpanzee’s DNA

Chimpanzee

100%96%92%

Human

Gibbon

Orangutan

Gorilla

Primate

Old World

monkey

Figure 13.10

Neo-Darwinism = The Modern SynthesisNeo-Darwinism = The Modern Synthesis evidence from evidence from Comparative BiochemistryComparative Biochemistry

We can calculate rates of mutation particularly in very stable We can calculate rates of mutation particularly in very stable genes or pseudogenes and use them as clocksgenes or pseudogenes and use them as clocks

Cytochrome C: yeast, wheat, humanCytochrome C: yeast, wheat, human

Neo-Darwinism = The Modern SynthesisNeo-Darwinism = The Modern Synthesis evidence from evidence from BiogeographyBiogeography

Pangaea

Pre

se

nt

Pa

leo

zoic

Ce

no

zoic

Me

so

zoic

25

1 m

illi

on

ye

ars

ag

o1

35

65

Laurasia

Gondwana

Eurasia

India

Madagascar

North Americ

a

Africa

South

America

Antarctica Australia

Figure 14.17

Neo-Darwinism = The Modern SynthesisNeo-Darwinism = The Modern Synthesisevidence from evidence from Paleontology (fossils)Paleontology (fossils)

Neo-Darwinism = The Modern SynthesisNeo-Darwinism = The Modern Synthesis

evidence from evidence from Paleontology: The Fossil RecordPaleontology: The Fossil Record

Fossil Fossil RecordRecord


evidence from evidence from Vestigial StructuresVestigial Structures

The Recurrent Laryngeal NerveThe Recurrent Laryngeal Nervevestiges, the “scars” of evolutionvestiges, the “scars” of evolution

The Recurrent Laryngeal NerveThe Recurrent Laryngeal Nervevestiges, the “scars” of evolutionvestiges, the “scars” of evolution





Does Evolution occur by Does Evolution occur by mechanisms other than mechanisms other than

natural selection?natural selection? YES. Evolution can…YES. Evolution can…

be slow or fast;be slow or fast; and it can be helpful, harmful or neutral.and it can be helpful, harmful or neutral.

Does Evolution occur by mechanisms Does Evolution occur by mechanisms other than natural selection?other than natural selection?

OK, how about this question…OK, how about this question…

Does Evolution Does Evolution notnot occur? occur?

What’s necessary for equilibrium?What’s necessary for equilibrium?

NO mutation NO mutation

NO gene flow NO gene flow

NO genetic drift NO genetic drift

NO nonrandom mating (i.e. totally random mating)NO nonrandom mating (i.e. totally random mating)

NO natural selectionNO natural selection

A large population.A large population.

ALL OF THESE CONDITIONS OCCURRING SIMULTANEOUSLY IS UNLIKELY!ALL OF THESE CONDITIONS OCCURRING SIMULTANEOUSLY IS UNLIKELY!

Analyzing Gene PoolsAnalyzing Gene Pools The gene pool is a reservoir from which the next The gene pool is a reservoir from which the next

generation draws its genes.generation draws its genes. Alleles in a gene pool occur in certain frequencies.Alleles in a gene pool occur in certain frequencies. When thinking about evolution, think When thinking about evolution, think gene pool gene pool !!

Evolution is a change in the genetic make-up of a POPULATION (gene pool)


natural selection?natural selection? The 3 main causes of evolutionary change are:The 3 main causes of evolutionary change are:

• Genetic driftGenetic drift• Gene flowGene flow• Natural selection (only natural selection is adaptive)Natural selection (only natural selection is adaptive)


natural selection?natural selection? Let’s look at Let’s look at Genetic DriftGenetic Drift.. Just consider the two words:Just consider the two words:

Natural Natural SelectionSelection

vs.vs. Genetic Genetic DriftDrift

Genetic DriftGenetic Drift Genetic driftGenetic drift is: is:

• A change in the gene pool of a small populationA change in the gene pool of a small population• Due to Due to chance events..• Compare the words: “drift” vs “selection.”Compare the words: “drift” vs “selection.”

Genetic DriftGenetic Drifte.g. Founder Effect and Bottleneck Effecte.g. Founder Effect and Bottleneck Effect

Genetic DriftGenetic Drift

Oreaster reticularum Oreaster reticularum in Bahamas…in Bahamas… Non-random matingNon-random mating

Examples from textbook…Examples from textbook… Non-random mating (small population of Non-random mating (small population of

flowers)flowers) Bottleneck Effect (cheetahs)Bottleneck Effect (cheetahs) Founder Effect (humans on Tristan da Cahuna)Founder Effect (humans on Tristan da Cahuna)

The Caribbean Cushion StarThe Caribbean Cushion Star• A change in the gene pool of a A change in the gene pool of a smallsmall population population• Due to chanceDue to chance

Figure 13.19

Flower Example from TextFlower Example from Text

Only 5 of

10 plants

leave

offspring

RR

rr

Rr

RR

RR

RR

RR Rr

RR

Rr

Rr

Only 2 of

10 plants

leave

offspring

RR

rr RR

Rr

rr

RR

Rr

Rr Rr

rr

RR

RR

RR

RR

RR

RR

RR

RRRR

Generation 1

p (frequency of R)) 0.7

q (frequency of (r) 0.3

Generation \22

p 0.5

q 0.5

Generation 3

p 1.0

q 0.0

Figure 13.22-3

Genetic Drift is: A change in the gene pool of a small

population, …due to chance

The Bottleneck EffectThe Bottleneck Effect The The bottleneck effectbottleneck effect::

• Is an example of genetic drift Is an example of genetic drift • Results from a drastic reduction in population size Results from a drastic reduction in population size

often due to some catastrophic event.often due to some catastrophic event.

Original

population

Bottlenecking

event

Surviving

population

The Bottleneck EffectThe Bottleneck Effect The The bottleneck effectbottleneck effect::

• Is an example of genetic drift Is an example of genetic drift • Results from a drastic reduction in population sizeResults from a drastic reduction in population size• The hunting of large cats like the cheetahThe hunting of large cats like the cheetah

Bottlenecking in a population usually reduces Bottlenecking in a population usually reduces genetic variation because at least some alleles are genetic variation because at least some alleles are likely to be lost from the gene pool.likely to be lost from the gene pool.

Cheetahs appear to have experienced at least two Cheetahs appear to have experienced at least two genetic bottlenecks in the past 10,000 years.genetic bottlenecks in the past 10,000 years.

The Founder EffectThe Founder Effect The The founder effectfounder effect is likely when a few individuals is likely when a few individuals

colonize an isolated habitat and represent genetic colonize an isolated habitat and represent genetic drift in a new colony.drift in a new colony.

The founder effect explains the relatively high The founder effect explains the relatively high frequency of certain inherited disorders among frequency of certain inherited disorders among some small human populations.some small human populations.• Huntington’s Disease around Lake Maracaibo VenezuelaHuntington’s Disease around Lake Maracaibo Venezuela• Hereditary blindness on Tristan da CuhanaHereditary blindness on Tristan da Cuhana• Galapagos species (drift + selection)Galapagos species (drift + selection)

Founder EffectFounder Effect

South

America

Tristan da

Cunha

Africa

Figure 13.25

Gene FlowGene Flow

Gene flow:Gene flow:• Is genetic exchange with another population Is genetic exchange with another population • Tends to reduce genetic differences between populationsTends to reduce genetic differences between populations

Three General Outcomes of Three General Outcomes of Natural SelectionNatural Selection

Directional selection:Directional selection:• Shifts the phenotypic “curve” of a population Shifts the phenotypic “curve” of a population • Selects in favor of some extreme phenotypeSelects in favor of some extreme phenotype

Disruptive selection:Disruptive selection: • can lead to a balance between two or more contrasting can lead to a balance between two or more contrasting

phenotypic forms in a population.phenotypic forms in a population.

Stabilizing selection:Stabilizing selection:• Favors intermediate phenotypes Favors intermediate phenotypes • Is the most commonIs the most common

Original

population

Evolved

population

Phenotypes (fur color)

Fre

qu

ency

of

ind

ivid

ual

sOriginal

population

(a) Directional selection (b) Disruptive selection (c) Stabilizing selection

Sexual SelectionSexual Selection Sexual dimorphismSexual dimorphism is: is:

• A distinction in appearance between males and femalesA distinction in appearance between males and females• Not directly associated with reproduction or survivalNot directly associated with reproduction or survival

Sexual selectionSexual selection is a form of natural selection in which is a form of natural selection in which inherited characteristics determine mating preferences.inherited characteristics determine mating preferences.

(a) Sexual dimorphism in

a finch species

(b) Competing for mates

Figure 13.29

(a) Sexual dimorphism in a finch species

Figure 13.29a

(b) Competing for mates

Figure 13.29b

Population Genetics and Health SciencePopulation Genetics and Health Science The Hardy-Weinberg formula can be used to The Hardy-Weinberg formula can be used to

calculate the percentage of a human population that calculate the percentage of a human population that carries the allele for a particular inherited disease.carries the allele for a particular inherited disease.

Go over this in book on your own.Go over this in book on your own.

END OF CHAP 13END OF CHAP 13ON TO CHAP 14ON TO CHAP 14

Old slidesOld slides

PKU:PKU:• Is a recessive allele that prevents the breakdown of the Is a recessive allele that prevents the breakdown of the

amino acid phenylalanineamino acid phenylalanine• Occurs in about one out of every 10,000 babies born in the Occurs in about one out of every 10,000 babies born in the

United StatesUnited States

INGREDIENTS: SORBITOL,

MAGNESIUM STEARATE,

ARTIFICIAL FLAVOR

INGREDIENTS: SORBITOL,

MAGNESIUM STEARATE,

ARTIFICIAL FLAVOR

ASPARTAME† (SWEETENER),

† PHENYLKETONURICS:

CONTAINS PHENYLALANINE

The Hardy-Weinberg formula can be The Hardy-Weinberg formula can be used to calculate the frequencies of used to calculate the frequencies of genotypes in a gene pool from the genotypes in a gene pool from the

frequencies of alleles.frequencies of alleles.

((pp++qq))22 = = pp22 + + 2pq2pq + + qq22 = 1 = 1

Let’s do a simple analysis of a gene poolLet’s do a simple analysis of a gene pool::

Set these conditions: Set these conditions: Just one trait, (let’s say fur color)Just one trait, (let’s say fur color) With just two alleles, B + rWith just two alleles, B + r And one dominant (B) and the other recessive (r)And one dominant (B) and the other recessive (r)

Let’s say the genes exist the in the gene pool at 50-50.Let’s say the genes exist the in the gene pool at 50-50.

The Hardy-Weinberg formula can be The Hardy-Weinberg formula can be used to calculate the frequencies of used to calculate the frequencies of genotypes in a gene pool from the genotypes in a gene pool from the

frequencies of alleles.frequencies of alleles.

((pp++qq))22 = = pp22 + + 2pq2pq + + qq22 = 1 = 1

((BB++rr))22 = = BB22 + + 2Br2Br + + rr22 = 1 = 1

So, p = B = black, the dominant gene

And q = r = red the recessive gene

Shuffle up and deal…

HardyHardy WeinbergWeinberg

What is YOUR genotype?What is YOUR genotype? What is YOUR phenotype?What is YOUR phenotype? What alleles do YOU have?What alleles do YOU have? What is the population’s gene frequencies What is the population’s gene frequencies

for B? for r?for B? for r?

Hardy-Weinberg EquilibriumHardy-Weinberg Equilibrium

OK, mate (randomly). Give a gamete to OK, mate (randomly). Give a gamete to anyone else until everyone has two. anyone else until everyone has two.

Has anything changed in the gene pool?Has anything changed in the gene pool?

Has anything changed? Has anything changed? Has the population evolved?Has the population evolved?

•

Genotype frequencies:Genotype frequencies:• Can be calculated from allele frequencies Can be calculated from allele frequencies • Are symbolized by the expressions Are symbolized by the expressions pp22, 2, 2pqpq, and , and qq22

To refresh our memories, consider the more complex but To refresh our memories, consider the more complex but familiar multiple-allele Human ABO Blood Types…familiar multiple-allele Human ABO Blood Types…

Neither A nor B is dominant to the other, o is recessive.Neither A nor B is dominant to the other, o is recessive.

A, B, O are the A, B, O are the three allelesthree alleles

AA, Ao, BB, Bo, AB, oo are the AA, Ao, BB, Bo, AB, oo are the six genotypessix genotypes

Type A, Type B, Type AB and Type O are the Type A, Type B, Type AB and Type O are the four four phenotypes.phenotypes.

Examples of Evolution by Natural Selection Microevolution vs. Macroevolution Microevolution is intraspecific evolution, evolution WITHIN a species. Microevolution.

Documents

intraspecific evolution

rapid evolution

natural selectionexample

way darwinian evolution

species resistant

new species

species of plants

species of british moths