Why is life on Earth so diverse??? TEST: Friday 10/28.

Why is life Why is life on Earth on Earth

so so diverse???diverse???

TEST: Friday 10/28

EvolutionEvolution► Change over timeChange over time► Descent with modificationDescent with modification► Genetic traits passed on to offspringGenetic traits passed on to offspring

Charles Darwin &Charles Darwin &The Voyage of the BeagleThe Voyage of the Beagle

► In 1831 he traveled In 1831 he traveled around the world on a around the world on a ship called the ship called the BeagleBeagle

► He noticed that there He noticed that there was was great diversitygreat diversity in in organisms even in very organisms even in very similar environmentssimilar environments

► The The Galapagos IslandsGalapagos Islands had the biggest impact had the biggest impact on Darwin’s studies.on Darwin’s studies.

Darwin’s JourneyDarwin’s Journey

What did Darwin See??What did Darwin See??

What did Darwin see?????What did Darwin see?????

What did Darwin see?????What did Darwin see?????

Glyptodon (fossil)

Evidence of EvolutionEvidence of EvolutionDarwin saw many things which Darwin saw many things which

influenced his theories……influenced his theories……1.1. Fossil Record, the Earth was Fossil Record, the Earth was reallyreally old old

(estimated at 4.5 billion years) (estimated at 4.5 billion years)

2.2. Lamark’s misconceptions on use and Lamark’s misconceptions on use and disuse of adaptations (crab)disuse of adaptations (crab)

3.3. Populations did not grow out of Populations did not grow out of control, there were factors that control, there were factors that limited population growthlimited population growth

Evidence of EvolutionEvidence of Evolution

► FossilFossil RecordsRecords--fossils being fossils being discovered discovered were evidence were evidence that the world that the world was much was much older that once older that once thought.thought.

99% of species that once lived are now extinct!!!!!!Did

you

know????Some fossils were very

similar to modern day creatures

FossilsFossils show history of life on Earthshow history of life on Earth

Relative Relative DatingDating -The -The layering of layering of rock can rock can show which show which fossils are fossils are older.older.

FossilsFossils show history of life on Earthshow history of life on Earth

Radioactive DatingRadioactive Dating -using the half-life of radioactive -using the half-life of radioactive elements scientists can tell how old a fossil is.elements scientists can tell how old a fossil is.

Lamark’s TheoryLamark’s Theory► Lamark believed organisms could adapt to fit their Lamark believed organisms could adapt to fit their

environment (ex: fiddler crab)environment (ex: fiddler crab)

•Problem was that he Problem was that he didn’t know about how didn’t know about how traits are passed on traits are passed on geneticallygenetically

•His idea that animals are His idea that animals are adapted to their environment adapted to their environment influenced Darwin’s idea on influenced Darwin’s idea on adaptationsadaptations

WRONG

Darwin’s Observations:Darwin’s Observations:1.1. organisms produce so many offspring that their organisms produce so many offspring that their

population size would increase exponentially if all population size would increase exponentially if all individuals that are born reproduce successfully. individuals that are born reproduce successfully. (Green bean analogy)(Green bean analogy)

2.2. populations tend to remain stable in size, except for populations tend to remain stable in size, except for seasonal fluctuations. seasonal fluctuations.

3.3. environmental resources are limited. environmental resources are limited.

POPULATION GROWTH

AHA!!!....Darwin said “It is AHA!!!....Darwin said “It is SURVIVAL OF THE FITTESTSURVIVAL OF THE FITTEST””

Darwin’s Inference:Darwin’s Inference:Production of more individuals than the environment Production of more individuals than the environment can support leads to a can support leads to a struggle for existencestruggle for existence, with , with only a fraction of offspring surviving.only a fraction of offspring surviving.

““ORIGIN OF SPECIES”ORIGIN OF SPECIES”In 1859, after 25 years of work, Darwin publishes his work In 1859, after 25 years of work, Darwin publishes his work

to much ridicule.to much ridicule.

Theory of Natural SelectionDarwin proposes that the diversity of life has evolved because the most fit organism in an environment survives and is able to pass on these fitness traits.

Adaptations are characteristics which allow organisms the ability to best survive in their ecosystem.

Pinta IslandIntermediate shell

Hood IslandSaddle-backed shell

Isabela IslandDome-shaped shell

Darwin’s Theory is supported by….Darwin’s Theory is supported by….

ARTIFICIAL SELECTIONARTIFICIAL SELECTION► Nature provides Nature provides

variation but variation but humans decide humans decide what traits are what traits are selected and selected and passed on.passed on.

► Hybridization brings Hybridization brings about new about new variationsvariations

donkey meets horse...

.

donkey meets horse...

.

mule offspring (sterile)

mule offspring (sterile)

Darwin new there was much variation in nature….Darwin new there was much variation in nature….

Descent with ModificationDescent with ModificationDarwin proposes that after long periods of time, natural selection results in organisms which are very different from their ancestor.

•Different structures

•Different niches

•Different habitatsCOMMON

ANCESTOR

Reasons for….Reasons for….

Descent with ModificationsDescent with Modifications

Reason for Genetic Reason for Genetic VariabilityVariability

►Sexual reproductionSexual reproduction►MutationsMutations►MigrationsMigrations►Natural SelectionNatural Selection►Genetic DriftGenetic Drift

Other Evidence for Evolution…Other Evidence for Evolution…

EmbryologyEmbryology

Embryos tend Embryos tend to look very to look very similar at similar at early stages early stages and cells and cells develop into develop into homologous homologous structures.structures.

EmbryologyEmbryology


Homologous StructuresHomologous Structures

Traits that are similar in different species because the species share a common ancestor.►Same structure, different functionSame structure, different function

Analagous StructuresAnalagous Structures

►Analogous StructuresAnalogous Structures: structures : structures similar in function, but similar in function, but not inherited not inherited from a common ancestorfrom a common ancestor. Share . Share similar environments.similar environments.

►Same function, different structureSame function, different structure


Vestigial OrgansVestigial OrgansTraces of organs, inherited from ancestors, Traces of organs, inherited from ancestors,

that seem to have no functional purposethat seem to have no functional purpose

►Hip joint in whales, snakesHip joint in whales, snakes►Ear muscles in humansEar muscles in humans►Male nipplesMale nipples►TailboneTailbone


Geographic DistributionGeographic Distribution

► When similar When similar

environments produce environments produce

similar looking similar looking

organisms that are organisms that are

unrelated.unrelated.

Beaver

Capybara

Muskrat

Coypu

Beaver

Muskrat

Beaver andMuskrat

Coypu

Capybara

Coypu andCapybara


Biochemical EvidenceBiochemical Evidence•All living things use DNA/RNA as their genetic code

•There is very little difference in DNA sequences of most organisms

Why is life on Earth so diverse??? TEST: Friday 10/28.

Documents

Transcript of Why is life on Earth so diverse??? TEST: Friday 10/28.