What is Evolution?What is Evolution? Change over timeChange over time The theory of evolution proposes that The theory of evolution proposes that

modern forms of life have descended modern forms of life have descended from earlier forms of life and changed from earlier forms of life and changed as they descended. as they descended.

What caused the “changes” or What caused the “changes” or differences in traits?differences in traits? MUTATIONS!!MUTATIONS!!

Can we control this?Can we control this?

Why is the Theory of Evolution so Why is the Theory of Evolution so Controversial?Controversial?

People have varying beliefs on the People have varying beliefs on the origin of life due to religion.origin of life due to religion.

Biological evolution Biological evolution does not does not study study the origin of life. It only studies the the origin of life. It only studies the changes in life forms since their changes in life forms since their origin.origin.

Mechanisms that drive evolution?Mechanisms that drive evolution? MutationMutation= random changes in the DNA= random changes in the DNA Natural SelectionNatural Selection Gene FlowGene Flow= movement of alleles into or out of a population = movement of alleles into or out of a population Genetic driftGenetic drift= changes in the alleles of a population due to = changes in the alleles of a population due to

random events (i.e. natural disaster. random events (i.e. natural disaster. Important terms to know:Important terms to know:• adaptationadaptation- A characteristic that increases fitness.- A characteristic that increases fitness.• fitnessfitness- The ability to survive and reproduce.- The ability to survive and reproduce.

What is natural selection?What is natural selection? A theory introduced by Charles DarwinA theory introduced by Charles Darwin A process that increases or decreases the presence of A process that increases or decreases the presence of

a trait depending on the trait’s ability to keep the a trait depending on the trait’s ability to keep the organism alive and reproducing.organism alive and reproducing.

3 conditions must be met for natural selection to occur:3 conditions must be met for natural selection to occur: Variation in characteristics (due to mutations)Variation in characteristics (due to mutations) Differences in fitnessDifferences in fitness Heritability (can be passed down to offspring) of the Heritability (can be passed down to offspring) of the

characteristiccharacteristic

Examples of Natural Selection Examples of Natural Selection Galapagos finches= different beaksGalapagos finches= different beaks Male peacocks= varying brightness in their feathersMale peacocks= varying brightness in their feathers Giraffes= varying neck lengthGiraffes= varying neck length Sharks= white on the underside and blue/gray on topSharks= white on the underside and blue/gray on top Humans= varying resistance to malariaHumans= varying resistance to malaria Bacteria= antibiotic resistanceBacteria= antibiotic resistance

Natural Selection LabNatural Selection Lab

Natural Selection LabNatural Selection Lab

How do we know if evolution has How do we know if evolution has occurred? occurred?

The The Hardy-WeinbergHardy-Weinberg Principle calculates genetic variety in Principle calculates genetic variety in a population. If the genetic variety remains constant from a population. If the genetic variety remains constant from one generation to the next, it is said to be in Hardy-one generation to the next, it is said to be in Hardy-Weinberg equilibrium (not evolving). Weinberg equilibrium (not evolving).

The H-W equation is:The H-W equation is:pp22 + 2pq + q + 2pq + q22= 1 (or 100%)= 1 (or 100%)p + q= 1p + q= 1

Hardy-Weinberg continued…Hardy-Weinberg continued…qq22= the frequency of homozygous = the frequency of homozygous recessive recessive individuals.individuals.2pq = the frequency of heterozygous 2pq = the frequency of heterozygous individuals.individuals.pp22= the frequency of homozygous = the frequency of homozygous dominant dominant individuals.individuals.

p= the frequency of the dominant allele.p= the frequency of the dominant allele.q= the frequency of the recessive allele.q= the frequency of the recessive allele.

Hardy-Weinberg continued…Hardy-Weinberg continued…Five conditions must be met for a population to remain in Five conditions must be met for a population to remain in H-W equilibrium:H-W equilibrium:•Random matingRandom mating•No movement of members into or out of the populationNo movement of members into or out of the population•No natural selectionNo natural selection•No mutationsNo mutations•Population must be largePopulation must be large

Hardy-Weinberg PracticeHardy-Weinberg Practice

Brown hair (B) is dominant to blonde hair (b). If Brown hair (B) is dominant to blonde hair (b). If there are 168 brown-haired people in a there are 168 brown-haired people in a population of 200, what are the frequencies of population of 200, what are the frequencies of homozygous dominant, homozygous recessive homozygous dominant, homozygous recessive and heterozygous individuals?and heterozygous individuals?

Hardy-Weinberg Goldfish LabHardy-Weinberg Goldfish Lab

Another H-W problemAnother H-W problemTongue rolling is a dominant trait. Who Tongue rolling is a dominant trait. Who in the class is homozygous recessive (tt) in the class is homozygous recessive (tt) and cannot roll his/her tongue? What are and cannot roll his/her tongue? What are the pthe p22, 2pq and q, 2pq and q22 values for the class? values for the class?

CladogramCladogram Evolutionary relatedness between organisms can be demonstrated Evolutionary relatedness between organisms can be demonstrated

on a diagram called a on a diagram called a cladogramcladogram.. Organisms with similar characteristics are placed more closely on Organisms with similar characteristics are placed more closely on

the diagram because they are thought to have evolved more the diagram because they are thought to have evolved more closely to one another.closely to one another.

As an organism evolves, there is a new branch on the cladogram.As an organism evolves, there is a new branch on the cladogram. Characteristics that evolve between species are called Characteristics that evolve between species are called derived derived

characterscharacters..

One more H-W problemOne more H-W problemCalculate the pCalculate the p22, 2pq and q, 2pq and q22 values when values when 14 out of 113 members of a population 14 out of 113 members of a population have the recessive trait for left have the recessive trait for left handedness.handedness.

Evidence of Common AncestryEvidence of Common Ancestry The theory of evolution states that all living things have The theory of evolution states that all living things have

descended from another life form, just as you have descended descended from another life form, just as you have descended from your parents and they descended from their parents.from your parents and they descended from their parents.

The evidence that supports this theory includes:The evidence that supports this theory includes: FossilsFossils DNA DNA Embryo structureEmbryo structure Comparative anatomyComparative anatomy

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Evidence of Common Ancestry- Fossil Record

Layers of rock contain fossils new layers cover older ones

creates a fossil record over time fossils show a series of organisms that

have lived on Earth

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Evolution from sea to land Fossils are also evidence of transitional (in between) forms. In 2006, there was the fossil discovery of the missing link between sea and

land animals 4 limbs called Tiktaalik

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Evidence of Common Ancestry- Comparative Anatomy

Animals with different structures on the surfaceAnimals with different structures on the surface

But when you look under the skin…But when you look under the skin…

It tells an evolutionary story of common ancestorsIt tells an evolutionary story of common ancestors

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Compare the bones

Limbs of different animals that perform different functions are built with the same bone structure

How could thesevery different animals

have the same bones?

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Homologous structures Structures that come from the same origin

homo = same logous = information

Forelimbs of humans, cats, whales, & bats are homologous structures. same internal structure but different

functions evidence of common ancestor The greater the # of homologous structures

between organisms, the more closely related they are.

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But don’t be fooled by these…

Analogous structures look similar on the outside have the same function different internal structure This means they do not have a close

evolutionary relationshipHow is a birdlike a bug?

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Vestigial organs Structures of modern animals that have

no function evolutionists believe that these were

functional in ancestors evidence of change over time

some snakes & whales have pelvis bones & leg bones of walking ancestors

eyes on blind cave fish

human tail bone

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Vestigial organs Hind leg bones on whale fossils

Why would whales have pelvis & leg bones if they were always sea creatures?

Why would whales have pelvis & leg bones if they were always sea creatures?

Because they used to

walk on land!

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Evidence of Common Ancestry- Embryology

Development of an embryo tells an evolutionary story The greater the # of similar structures during embryo

development, the more closely related they are.

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Evidence of Common Ancestry-Biochemistry

100 20 30 40 50 60 70 80 90 100 110 120

LampreyFrogBirdDogMacaqueHuman

328 45 67 125

Comparing DNA & protein structure Every living thing uses the same

genetic code!

The fewer the number of differences in the amino acid sequence of common proteins, the more closely related organisms are.

The fewer the number of differences in the amino acid sequence of common proteins, the more closely related organisms are.

number of amino acids different from human hemoglobinnumber of amino acids different from human hemoglobin

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  Horse Chicken Tuna Frog Shark Turtle Monkey Rabbit

Human 6 6 9 8 

14 8 1 4

Rabbit 5 

5 

9 6 12 7 5 X

Monkey 7 

8 10 8 13 9 X X

Turtle 7 

2 9 5 12 X X X

Shark 11 

12 12 12 X X X X

Frog 8 

3 8 X X X X X

Tuna 11 

7 X X X X X X

Chicken 7 

X X X X X X X

•What 2 organisms on the chart above are the most alike in terms of DNA?•What 2 organisms are the least alike?•What is the turtle’s closest relative? Why does this data make sense?

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What data from whole genome sequencing can tell us about evolution of humans

What data from whole genome sequencing can tell us about evolution of humans

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Example: the Evolutionary Hypothesis

of Common Ancestry

Chromosome Numbers in the great apes:

human (Homo) 4646chimpanzee (Pan) 48gorilla (Gorilla) 48orangutan (Pogo) 48

Testable prediction:Testable prediction: If these organisms share a common ancestor, that ancestor had either 48 chromosomes (24 pairs) or 46 (23 pairs).

Testable prediction:Testable prediction: If these organisms share a common ancestor, that ancestor had either 48 chromosomes (24 pairs) or 46 (23 pairs).

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Chromosome Numbers in the great apes (Hominidae):

human (Homo) 46chimpanzee (Pan) 48gorilla (Gorilla) 48orangutan (Pogo) 48

Testable prediction:Testable prediction: Common ancestor had 48 chromosomes (24 pairs) and humans carry a fused chromosome; or ancestor had 23 pairs, and apes carry a split chromosome.

Centromere

Telomere

Ancestral Chromosomes

FusionHomo sapiens

Inactivated centromere

Telomere sequences

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“Chromosome 2 is unique to the human lineage of evolution, having emerged as a result of head-to-head fusion of two acrocentric chromosomes that remained separate in other primates. The precise fusion site has been located in 2q13–2q14.1 (ref. 2; hg 16:114455823 – 114455838), where our analysis confirmed the presence of multiple subtelomeric duplications to chromosomes 1, 5, 8, 9, 10, 12, 19, 21 and 22 (Fig. 3; Supplementary Fig. 3a, region A). During the formation of human chromosome 2, one of the two centromeres became inactivated (2q21, which corresponds to the centromere from chimp chromosome 13) and the centromeric structure quickly deterioriated (42).”

“Chromosome 2 is unique to the human lineage of evolution, having emerged as a result of head-to-head fusion of two acrocentric chromosomes that remained separate in other primates. The precise fusion site has been located in 2q13–2q14.1 (ref. 2; hg 16:114455823 – 114455838), where our analysis confirmed the presence of multiple subtelomeric duplications to chromosomes 1, 5, 8, 9, 10, 12, 19, 21 and 22 (Fig. 3; Supplementary Fig. 3a, region A). During the formation of human chromosome 2, one of the two centromeres became inactivated (2q21, which corresponds to the centromere from chimp chromosome 13) and the centromeric structure quickly deterioriated (42).”

Homo sapiens

Inactivated centromere

Telomere sequences

Hillier et al (2005) “Generation and Annotation of the DNA sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731.

Hillier et al (2005) “Generation and Annotation of the DNA sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731.

Human Chromosome #2 shows the exact point at which this fusion took place

Human Chromosome #2 shows the exact point at which this fusion took place

Chr 2

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Building “family” treesEvolution evidence can be used to create family trees. Closely related species are branches on the tree — coming from a common ancestor

Evolution evidence can be used to create family trees. Closely related species are branches on the tree — coming from a common ancestor

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Human Impact on Evolution- Selective Breeding

Humans create the change over timeHumans create the change over time

“descendants” of the wolf“descendants” of the wolf

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Artificial Selection…and the examples keep coming!

I liked breeding pigeons!

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Insecticide resistance

Human activities like spraying crop fields with insecticides leads to: The survival of insects that are

resistant to the insecticide Resistant survivors reproduce Resistance is inherited Insecticide becomes less & less

effective

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