EVOLUTIONEVOLUTIONObjectives:Objectives:

1.1. Explain how natural selection works?Explain how natural selection works?

2. 2. What observations did Darwin helped him What observations did Darwin helped him develop the theory of evolution?develop the theory of evolution?

3.3. What does adaptation mean? Give an What does adaptation mean? Give an example of an organism adapting to its example of an organism adapting to its environment.environment.

QuizQuiz

1.1. What don’t harmful mutations accumulate What don’t harmful mutations accumulate over time?over time?

2.2. Why can we use observations of bacteria as Why can we use observations of bacteria as evidence of evolution?evidence of evolution?

3.3. What is the difference between a hypothesis What is the difference between a hypothesis and a theory?and a theory?

4.4. What is selective breeding?What is selective breeding?

Early theories (pre-1700’s)Early theories (pre-1700’s) Before Darwin, nature was seen as not Before Darwin, nature was seen as not

changing but as having originated through changing but as having originated through spontaneous generation.spontaneous generation.

1700’s1700’s An understanding of the age of the Earth develops An understanding of the age of the Earth develops

through geology. through geology. The Earth has been and is still gradually changing.The Earth has been and is still gradually changing.

Inheritance of acquired traits (use and disuse).Inheritance of acquired traits (use and disuse).

ex. Baby giraffes are born with long necks because ex. Baby giraffes are born with long necks because their parents stretched their necks to reach leaves their parents stretched their necks to reach leaves (Jean-Baptiste Lamarck, 1801)(Jean-Baptiste Lamarck, 1801)

MisconceptionMisconception

Genetics and the Passing on of Traits

Living organisms pass on their traits to their offspring.

Today’s species came about through gradual change.

What drove that change?

SURVIVAL/SEX/!!!!

Darwin and the Voyage of the Darwin and the Voyage of the BeagleBeagle

December, 1831’s, Charles Darwin, a December, 1831’s, Charles Darwin, a naturalist in his 20’s began a 5-year naturalist in his 20’s began a 5-year journey around the world on a ship called journey around the world on a ship called HMS BeagleHMS Beagle

Darwin’s role was to Darwin’s role was to observe, record, and observe, record, and collect specimens of collect specimens of rocks, minerals, plants, and animalsrocks, minerals, plants, and animals

Darwin collected 1000’s of specimens and Darwin collected 1000’s of specimens and shipped them to England, mainly from South shipped them to England, mainly from South America and a chain of volcanic islands called America and a chain of volcanic islands called GalapagosGalapagos

He did not realize what he was seeing until He did not realize what he was seeing until years later (ex. didn’t catalogue the finches very years later (ex. didn’t catalogue the finches very well, ate turtles that would later support his well, ate turtles that would later support his theories, etc.)theories, etc.)

Darwin spent the next 20 yrs analyzing his Darwin spent the next 20 yrs analyzing his findings in light of artificial selection (ex. findings in light of artificial selection (ex. breeding of pigeons, breeding of dogs, etc.)breeding of pigeons, breeding of dogs, etc.)

Darwin’s FinchesDarwin’s Finches

ArrivalArrival SuccessSuccess CompetitionCompetition Diversity & Diversity &

OpportunityOpportunity RadiationRadiation

Perhaps a single ancestral species Perhaps a single ancestral species transported from nearby land might give transported from nearby land might give rise to a number of similar but distinct new rise to a number of similar but distinct new species. species.

Hawaiian honeycreeperHawaiian honeycreeper

What Darwin Observed

1) Homologous Features

Homologous features: different functions, but similar structure (flippers, hands, wings)

All forelimbs of All forelimbs of vertebrates have the vertebrates have the same pattern of bonessame pattern of bones

ex. The ex. The flippers of flippers of whales, and whales, and the wings of the wings of birdsbirds

2) Analogous features: similar functions, but different structure (wings of birds and bees)

Darwin’s conclusion: organisms with homologous features likely shared a more recent ancestor, while those with analogous features do not!

3) Vestigial Features: non-functional structures that are homologous to fully functioning structures in closely related species.

Example: whales have pelvic bones that do not attach to legs

4) Similarities in Early Development (tailbones)

Goosebumps Darwin’s conclusion:

these ‘leftover’ features must have once had a use!

Other Evidence for Evolution…Other Evidence for Evolution…

Stuff that we have seen in our time…Stuff that we have seen in our time…

When comparing When comparing the DNA of one the DNA of one species to species to another, more another, more similarities are similarities are found in found in species that species that are more are more closely related.closely related.

Evidence for EvolutionEvidence for Evolution

The Fossil RecordThe Fossil Record-Layer -Layer show changeshow change

Shows numbers extinct animalsShows numbers extinct animals Shows similarities between extinct Shows similarities between extinct

animals and animals that are alive animals and animals that are alive todaytoday

The earth’s layers show a time The earth’s layers show a time scale of species and when they scale of species and when they appeared on earth (and when they appeared on earth (and when they died out)died out)

Transitional fossils Transitional fossils are fossils that are fossils that show intermediary show intermediary links between links between groups of groups of organismsorganisms

They can provide a They can provide a link between the link between the past and presentpast and present

Direct observation of species Direct observation of species change change

Bacteria become Bacteria become resistant to resistant to antibioticsantibiotics

Wolves were bred over Wolves were bred over many generations to many generations to become dogs (become dogs (artificial artificial selectionselection) • and then bred ) • and then bred further to create a variety further to create a variety of breedsof breeds

But how does evolution really But how does evolution really work???work???

How does evolution really work? How does evolution really work? http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html

What did Darwin think drove Evolution???

1) Artificial Selection Selecting offspring with desirable traits as

breeding stock for succeeding generations Example: corn with higher oil content

Darwin’s conclusion: if people could alter the appearance and behaviour of species through artificial selection, then the environment could have a similar selective effect on wild species!

Natural Selection & Artificial Natural Selection & Artificial SelectionSelection

Natural variationNatural variation--differences among --differences among individuals of a speciesindividuals of a species

Artificial selectionArtificial selection- nature provides the - nature provides the variation among different organisms, and variation among different organisms, and humans select those variations they find humans select those variations they find

usefuluseful..

Evolution by Natural SelectionEvolution by Natural Selection

The Struggle for ExistenceThe Struggle for Existence--members of each species have to members of each species have to compete for food, shelter, other life compete for food, shelter, other life necessitiesnecessities

Survival of the FittestSurvival of the Fittest-Some -Some individuals better suited for the individuals better suited for the environmentenvironment

The Struggle for Survival Plants and animals produce more offspring

than are able to survive Favourable variations would tend to be

preserved, unfavourable ones would be destroyed.

INTENSE COMPETITION!!!!!

Natural Selection as the Cause of EvolutionNatural Selection as the Cause of Evolution- called “natural selection” because it happens on - called “natural selection” because it happens on

its ownits own

1. Genetic Variation1. Genetic Variation

- there are many varieties of alleles- there are many varieties of alleles

- caused by random mutations- caused by random mutations

- can be passed onto offsprings (inherited variation)- can be passed onto offsprings (inherited variation)

2. Overproduction of Offsprings2. Overproduction of Offsprings

- organisms make too many offsprings- organisms make too many offsprings

3. Struggle for existence3. Struggle for existence- competition for limited resources- competition for limited resources

4. Differential survival and reproduction4. Differential survival and reproduction- only organisms that have certain - only organisms that have certain

characteristics will survive to reproduce characteristics will survive to reproduce - non-random, caused by the environment: - non-random, caused by the environment:

amount of food, competition (ex. Darwin’s amount of food, competition (ex. Darwin’s finches)finches)

PBS Evolution: The Evolutionary Arms PBS Evolution: The Evolutionary Arms Race (12 min)Race (12 min)

Answer questions on video.Answer questions on video.

Your task… (Due for tomorrow!!!)Your task… (Due for tomorrow!!!)

1.1. Read through the handout on Adaptation Read through the handout on Adaptation and Variationand Variation

2.2. Answer questions 1-5Answer questions 1-5

All of this takes a LOOOOOOONG All of this takes a LOOOOOOONG timetime