evolution. diversity of life there are millions of different kinds of organisms on earth. there are...

EvolutionEvolution

Diversity of LifeDiversity of Life

There are millions of different kinds of organisms There are millions of different kinds of organisms on Earth.on Earth.

This variety of living things is called This variety of living things is called biological biological diversity.diversity.

Diversity of LifeDiversity of Life

The theory of evolution helps to explain how all The theory of evolution helps to explain how all these different organisms arose. these different organisms arose.

Evolution is simply Evolution is simply change over timechange over time. . Charles DarwinCharles Darwin contributed more to our contributed more to our

understanding of evolution than anyone else!understanding of evolution than anyone else!

Charles DarwinCharles Darwin

Charles Darwin, at the Charles Darwin, at the age of 22, set off on a age of 22, set off on a journey that would journey that would change his life and the change his life and the way we think of way we think of ourselves. ourselves.

He took a job as a He took a job as a naturalist on a voyage on naturalist on a voyage on the the HMS BeagleHMS Beagle..

Darwin’s TripDarwin’s Trip

Wherever the ship anchored, Darwin went ashore to Wherever the ship anchored, Darwin went ashore to collect plant and animal specimens and collect plant and animal specimens and fossils, fossils, preserved remains of ancient organisms. preserved remains of ancient organisms.

Darwin’s TripDarwin’s Trip The place that The place that

influenced Darwin the influenced Darwin the most was a small most was a small chain of islands called chain of islands called the the Galapagos Galapagos IslandsIslands. .

They were very close They were very close together but had very together but had very different climates.different climates.

Darwin’s ObservationsDarwin’s Observations Darwin noticed that the Darwin noticed that the giant land tortoise’sgiant land tortoise’s on on

each island had a each island had a different shelldifferent shell..

Dome -shaped Saddle-shaped

Darwin’s ObservationsDarwin’s Observations He also noticed that birds calledHe also noticed that birds called finches finches had had

different shaped beaksdifferent shaped beaks depending on what depending on what island they were on.island they were on.

Darwin’s ObservationsDarwin’s Observations Darwin had observed that somewhat similar Darwin had observed that somewhat similar

species had traits that were also similar, but species had traits that were also similar, but suited them for the particular environment they suited them for the particular environment they lived in. lived in.

He began to wonder if species living on different He began to wonder if species living on different islands had once been the same species?islands had once been the same species?

The Evolution of a Theory After many observations of many species and After many observations of many species and

their geographical locations, Darwin started to their geographical locations, Darwin started to formulate his Theory of Evolution. formulate his Theory of Evolution.

Video 1: Isn’t evolution just a theory? Video 1: Isn’t evolution just a theory? http://www.pbs.org/wgbh/evolution/educators/

teachstuds/svideos.html

Darwin’s InfluencesDarwin’s Influences James Hutton and Charles LyellJames Hutton and Charles Lyell were geologists that were geologists that

helped scientists recognize that Earth was millions of helped scientists recognize that Earth was millions of years old, not young like others thought during their day.years old, not young like others thought during their day.

Darwin realized that if Earth was actually really old, that Darwin realized that if Earth was actually really old, that would have given time for evolution to have occurred. would have given time for evolution to have occurred.

James Hutton Charles Lyell

Darwin’s InfluencesDarwin’s Influences Jean-Baptiste LamarckJean-Baptiste Lamarck proposed that by selective use or disuse of organs, proposed that by selective use or disuse of organs,

species acquired or lost certain traits during their lifetime, and these new species acquired or lost certain traits during their lifetime, and these new traits were passed on to their offspring.traits were passed on to their offspring.

This was a good idea but not correct. Darwin’s idea of evolution was that it This was a good idea but not correct. Darwin’s idea of evolution was that it took a much longer amount of time to occur, not just a lifetime.took a much longer amount of time to occur, not just a lifetime.

Jean-Baptiste Lamarck

Darwin’s InfluencesDarwin’s Influences With the knowledge from Hutton, Lyell, Lamarck, and his With the knowledge from Hutton, Lyell, Lamarck, and his

own research on the Beagle, Darwin started working on own research on the Beagle, Darwin started working on his book, his book, On The Origin Of SpeciesOn The Origin Of Species..

He wrote this book and left it unpublished for 25 years! He wrote this book and left it unpublished for 25 years! Finally, he published it in 1859.Finally, he published it in 1859.

Who Was Darwin VideoWho Was Darwin Video Who Was Darwin?Who Was Darwin? Video 2 Video 2 http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

Darwin’s Theories on EvolutionDarwin’s Theories on Evolution Darwin included 4 major points about Darwin included 4 major points about

evolution:evolution:1.1. Inherited variation existsInherited variation exists within the within the

genes of every population or species.genes of every population or species. For example, some trees produce more For example, some trees produce more

oranges than others. oranges than others. Artificial Selection is when someone other Artificial Selection is when someone other

than nature selects, breeds, for a than nature selects, breeds, for a particular trait.particular trait.

Darwin’s Theories on EvolutionDarwin’s Theories on Evolution Darwin included 4 major points Darwin included 4 major points

about evolution:about evolution:

2.2. In a particular environment, some In a particular environment, some individuals of a population or individuals of a population or species are species are better suited, fit,better suited, fit, to to survive and have more offspring. survive and have more offspring. ((Natural selection/survival of the Natural selection/survival of the fittest).fittest).

Natural Selection (Survival of the Fittest)Natural Selection (Survival of the Fittest) Individuals that have physical or Individuals that have physical or

behavioral traits that better suit their behavioral traits that better suit their environment are more likely to survive and environment are more likely to survive and will reproduce more successfully than will reproduce more successfully than those that do not have such traits.those that do not have such traits.

Help with survival Camouflage – When an organism blends in with

its surroundings. Who will survive?

Help with survival Camouflage – When an organism blends in with

its surroundings.

Help with survival Mimicry – when an organism

copies the appearance of another species.

Monarch butterflies make birds that eat them really sick.

Viceroy butterflies are fine for birds to eat.

Birds however do not eat either!



3.3. Over time, the traits that make Over time, the traits that make certain individuals of a population certain individuals of a population able to survive and reproduce able to survive and reproduce tend to spread in that population tend to spread in that population ((descent with modificationdescent with modification).).



4.4. There is overwhelming evidence There is overwhelming evidence from from fossils, homologous fossils, homologous structuresstructures, similarities in , similarities in embryology, and DNAembryology, and DNA that living that living species evolved from organisms species evolved from organisms that are extinct.that are extinct.

How does evolution really work? Video 4 http://www.pbs.org/wgbh/evolution/educators/

teachstuds/svideos.html

Evidence of EvolutionEvidence of Evolution Evolution is change over time and is seen in the Evolution is change over time and is seen in the

fossil recordsfossil records. . By dating the sediments around the fossils, By dating the sediments around the fossils,

paleontologists can arrange the fossils from oldest paleontologists can arrange the fossils from oldest to youngest. to youngest.

What older rock layers tell us:What older rock layers tell us:

Evidence of EvolutionEvidence of EvolutionHomologous structuresHomologous structures – structures that – structures that

are similar in structure but different in are similar in structure but different in function. function.

Evidence of EvolutionEvidence of Evolution Example: the forelimbs of vertebrates contain the Example: the forelimbs of vertebrates contain the

same kinds of bones, which form the same way during same kinds of bones, which form the same way during embryological development, but are used differently embryological development, but are used differently when they mature.when they mature.

Evidence of Evolution Analogous structures – structures that are similar

in purpose but different in structure. Example: All of these are used to fly, but are different

in structure.

Evidence of Evolution Embryology –

the early stages of development are similar in different organisms.

Evidence of EvolutionEvidence of EvolutionVestigial StructuresVestigial Structures – bones or organs that – bones or organs that

are present in an organism but are are present in an organism but are reduced in size and either have no use or reduced in size and either have no use or have a less important function than they have a less important function than they do in other, related organisms. do in other, related organisms.

Evidence of EvolutionEvidence of EvolutionVestigial Structures Vestigial Structures

Example: hind limbs of whalesExample: hind limbs of whales..

Evidence of EvolutionEvidence of EvolutionVestigial Structures Vestigial Structures

Example: human appendixExample: human appendix..

Evidence of EvolutionEvidence of EvolutionHow do we know evolution happens?How do we know evolution happens?

Video 3 Video 3 http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

Evidence of EvolutionEvidence of EvolutionMolecular data (DNAMolecular data (DNA)– most important by far. )– most important by far.

Similar DNA shows similar relatedness.Similar DNA shows similar relatedness.

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Evidence of EvolutionEvidence of EvolutionDid Humans evolve? Video 5Did Humans evolve? Video 5

http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

4 Main Factors of Natural Selection4 Main Factors of Natural Selection1.1. All populations have All populations have genetic variationgenetic variation. .

Even if you cannot see it, there is an Even if you cannot see it, there is an array of variety in every species.array of variety in every species.

4 Main Factors of Natural Selection4 Main Factors of Natural Selection2.2. The The environment presents challengesenvironment presents challenges to to

successful reproduction. successful reproduction. If an organism does not survive or its If an organism does not survive or its

offspring die before they can offspring die before they can reproduce, their genes are not passed reproduce, their genes are not passed on to future generations.on to future generations.

4 Main Factors of Natural Selection4 Main Factors of Natural Selection3.3. Individuals tend to produce more Individuals tend to produce more

offspring than the environment can offspring than the environment can supportsupport. .

Individuals of a population will have Individuals of a population will have to compete with one another.to compete with one another.

4 Main Factors of Natural Selection4 Main Factors of Natural Selection4.4. Individuals that are better able to cope Individuals that are better able to cope

with the challenges presented by their with the challenges presented by their environment tend to leave more environment tend to leave more offspring than those individuals less offspring than those individuals less suited to the environment.suited to the environment.

Gene PoolAll species have a All species have a gene pool which includes gene pool which includes

all the different alleles for every gene in that all the different alleles for every gene in that population.population.

Gene PoolIn the gene pool, a trait controlled by a

single gene has less genotype and phenotype possibilities.

Gene PoolA trait controlled by polygenic gene has

many combinations of genotypes and phenotypes, this means more variety!

Genetic Equilibrium?If a population is left alone and nothing changes with it, the If a population is left alone and nothing changes with it, the

relative frequencies of the alleles in the gene pool never relative frequencies of the alleles in the gene pool never change.change.

Hardy-Weinberg Principle – allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change

Does this ever happen?

Causes of Genetic VariationCauses of Genetic Variation

However, there are situations that cause However, there are situations that cause these frequencies to change:these frequencies to change: The two main situations are:The two main situations are:

Mutations.Mutations.Gene shuffling in gamete formation Gene shuffling in gamete formation

(crossing over).(crossing over).

Causes of Genetic VariationCauses of Genetic Variation

Other sources that cause these Other sources that cause these frequencies to change are:frequencies to change are:Natural selection towards a particular Natural selection towards a particular

trait.trait.Genetic drift.Genetic drift.Nonrandom mating.Nonrandom mating.Small population size. Small population size.

Formation of New SpeciesFormation of New Species

A species can evolve to the point of A species can evolve to the point of becoming two or more new species. becoming two or more new species. This is known as This is known as speciation. speciation.

SpeciationStart with 1

species.Split it into 2

groups due to geographic isolation (separation by rivers, mountains, water, etc.).

SpeciationGive each group

a different environment and allow time to pass.

Speciation2 different

species have evolved and can no longer interbreed.

Speciation!

Speciation ExampleSpeciation Example

The Kaibab squirrel became isolated in the Grand Canyon about 10,000 years ago. Features have gradually evolved that separate it from its close relative, the Abert squirrel.


The accumulation of differences The accumulation of differences between groups is called between groups is called divergencedivergence..

Divergence leads to the formation of Divergence leads to the formation of new species.new species.


A second factor that can cause A second factor that can cause speciation is speciation is reproductive isolationreproductive isolation or or the loss of the ability of 2 species to the loss of the ability of 2 species to mate and produce viable, fertile mate and produce viable, fertile offspring.offspring.

Formation of New SpeciesFormation of New SpeciesConvergent Evolution Convergent Evolution – when different species – when different species

become more similar to each other. become more similar to each other. All of these different species are becoming All of these different species are becoming

better swimmers and their bodies are becoming better swimmers and their bodies are becoming more streamline. more streamline.

3 Types of Natural Selection3 Types of Natural Selection

Stabilizing SelectionStabilizing Selection – a type of – a type of selection in which genetic diversity selection in which genetic diversity decreases as the population size decreases as the population size stabilizes on a particular trait value.stabilizes on a particular trait value.

When individuals near the center of the When individuals near the center of the curve have higher fitness than individuals curve have higher fitness than individuals at either end of the curve.at either end of the curve.


Stabilizing SelectionStabilizing SelectionExample: Birth weight of babies.Example: Birth weight of babies.

If a baby is too small, it tends to get ill If a baby is too small, it tends to get ill quickly.quickly.

If a baby is too large, it is very difficult If a baby is too large, it is very difficult to deliver.to deliver.

A baby of medium size, however, A baby of medium size, however, does not get ill as quickly and is able does not get ill as quickly and is able to be delivered more often without to be delivered more often without harming the mother or the baby. harming the mother or the baby.


Stabilizing SelectionStabilizing SelectionIn essence, the trait’s frequency in a In essence, the trait’s frequency in a

population “stabilizes.” population “stabilizes.”


Stabilizing SelectionStabilizing Selection

Fre

quen

cy

of s

ize

(%)

Birth weight (pounds)

2 4 6 8 10 12 14 16

50

40

30

20

10 1st generation

1000’s of generations


Disruptive SelectionDisruptive Selection – a type of selection that – a type of selection that simultaneously favors individuals with a trait that simultaneously favors individuals with a trait that is found at one extreme of the population.is found at one extreme of the population.

When individuals at the upper and lower ends of the When individuals at the upper and lower ends of the curve have higher fitness than individuals near the curve have higher fitness than individuals near the middlemiddle


Disruptive SelectionDisruptive SelectionExample: Beaks of finches.Example: Beaks of finches.

If a beak is very small, the bird can If a beak is very small, the bird can easily pick up small seeds.easily pick up small seeds.

If a beak is very large, the bird can If a beak is very large, the bird can easily crack large seeds.easily crack large seeds.

If a beak is medium size, however, it If a beak is medium size, however, it cannot easily pick up seeds, nor can it cannot easily pick up seeds, nor can it easily crack large seeds. Thus, these easily crack large seeds. Thus, these birds are less adapted to their birds are less adapted to their environment and have lower fitness. environment and have lower fitness.


Disruptive SelectionDisruptive SelectionIn essence, the trait’s frequencies in a In essence, the trait’s frequencies in a

population “disrupt” a normal population “disrupt” a normal distribution. distribution.


Disruptive SelectionDisruptive Selection

Fre

quen

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of s

ize

(%)

Beak length (mm)

2 4 6 8 10 12 14 16

50

40

30

20

10

1st generation



Directional SelectionDirectional Selection – a type of selection that – a type of selection that favors a single phenotype and therefore the favors a single phenotype and therefore the allele frequency continuously increases.allele frequency continuously increases.

When individuals at one end of the curve have higher When individuals at one end of the curve have higher fitness than individuals in the middle or at the other end.fitness than individuals in the middle or at the other end.


Directional SelectionDirectional SelectionExample: Speed of greyhounds.Example: Speed of greyhounds.

If a dog was slow, owners would not If a dog was slow, owners would not breed them.breed them.

If a dog was fast, owners would breed If a dog was fast, owners would breed them.them.

Thus, over time, the frequency of fast Thus, over time, the frequency of fast dogs in the population increased. dogs in the population increased.


Directional SelectionDirectional SelectionIn essence, the trait’s frequency in a In essence, the trait’s frequency in a

population moves “directionally,” from population moves “directionally,” from low frequency to high frequency. low frequency to high frequency.


Directional SelectionDirectional Selection

Fre

quen

cy

of s

ize

(%)

Speed (mph)

2 4 6 8 10 12 14 16

50

40

30

20

101st generation


Evolutionary ChangesEvolutionary Changes

The speed of evolutionary changes can The speed of evolutionary changes can differ in 2 ways:differ in 2 ways:1.1. Gradualism Gradualism – the idea that evolution occurs – the idea that evolution occurs

gradually over a long period of time.gradually over a long period of time.

2.2. Punctuated EquilibriumPunctuated Equilibrium - the idea that - the idea that evolution occurs with periods of rapid evolution occurs with periods of rapid change which are separated by periods of change which are separated by periods of little or no change.little or no change.

Evolutionary ChangesEvolutionary ChangesCladograms help group organisms based Cladograms help group organisms based

on their evolutionary history and shows the on their evolutionary history and shows the order in which derived characteristics order in which derived characteristics evolved.evolved.

Importance of Evolution Now

Due to evolution, some strains of bacteria have become resistant to antibiotics!

Why does Evolution Matter Now? Video 6 http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

Why is Evolution Controversial? Video 7 http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

evolution. diversity of life there are millions of different kinds of organisms on earth. there are...

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