Evolution week 1 Darwin’s Theory & Natural Selection.

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Evolution week 1 Evolution week 1 Darwin’s Theory & Natural Darwin’s Theory & Natural Selection Selection

Transcript of Evolution week 1 Darwin’s Theory & Natural Selection.

Page 1: Evolution week 1 Darwin’s Theory & Natural Selection.

Evolution week 1Evolution week 1Darwin’s Theory & Natural SelectionDarwin’s Theory & Natural Selection

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EvolutionEvolution

Nothing in biology makes sense without Nothing in biology makes sense without the unifying concept of evolution!the unifying concept of evolution!

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Darwin Developed a theory of Darwin Developed a theory of EvolutionEvolution

A new view of life came into focus in 1859, A new view of life came into focus in 1859, when Charles Darwin published his book when Charles Darwin published his book The Origin of SpeciesThe Origin of Species..

On its grandest scale, evolution is all of On its grandest scale, evolution is all of the changes that have transformed life the changes that have transformed life over an immense time.over an immense time.

In a sense, evolution is the biological In a sense, evolution is the biological history of life on Earth.history of life on Earth.

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Before DarwinBefore Darwin

Before Darwin there were two ideals about life Before Darwin there were two ideals about life on Earthon Earth

1.1. One was that species were fixed, or permanentOne was that species were fixed, or permanent

2.2. The other was that the Earth was less than 10,000 The other was that the Earth was less than 10,000 years old and also relatively unchanged.years old and also relatively unchanged.

These ideals were challenged as people became These ideals were challenged as people became aware of the incredible diversity of organisms past aware of the incredible diversity of organisms past and present, and the nature of Earth’s geologic and present, and the nature of Earth’s geologic processess.processess.

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In the 1700’sIn the 1700’s

The study of fossils led by French The study of fossils led by French naturalist Geoges Buffon suggested that naturalist Geoges Buffon suggested that the Earth might be much older.the Earth might be much older.

Another scientist of the time – Lamarch, Another scientist of the time – Lamarch, was the 1was the 1stst to suggest that similarities to suggest that similarities between species are because they evolve. between species are because they evolve. His explanation was ultimately flawed. His explanation was ultimately flawed. Use and disuse.Use and disuse.

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Use or disuseUse or disuse

Lamarch also thought that living things Lamarch also thought that living things might have evolved. But, his reasoning might have evolved. But, his reasoning

was flawed in that he thought that was flawed in that he thought that acquired characteristics could be passedacquired characteristics could be passed

down from parent to offspring.down from parent to offspring.

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Voyage of the Beagle!Voyage of the Beagle!

On a cold December day in 1831, the HMS On a cold December day in 1831, the HMS Beagle set sail from England on a voyage Beagle set sail from England on a voyage around the world.around the world.

The main mission was to chart poorly known The main mission was to chart poorly known stretches of S. America for the British navy.stretches of S. America for the British navy.

Aboard was a 22-year old college graduate, Aboard was a 22-year old college graduate, Charles Darwin. There to study the geology, Charles Darwin. There to study the geology, plants and animals encountered on the trip.plants and animals encountered on the trip.

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Darwin’s ObservationsDarwin’s Observations

Plants and animals throughout the Plants and animals throughout the continent all had a definite south American continent all had a definite south American character.character.

Some of the fossils were gigantic forms of Some of the fossils were gigantic forms of modern animals.modern animals.

His observations supported his idea that His observations supported his idea that species living in S. America today were species living in S. America today were descendants from ancestral species on descendants from ancestral species on that continentthat continent

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The GalapagosThe Galapagos

The Galapagos are a chain (archipelago) The Galapagos are a chain (archipelago) of young islands 900 km of the west coast of young islands 900 km of the west coast of Ecuador, S. America.of Ecuador, S. America.

The Islands had similar plant and animal The Islands had similar plant and animal species to those found on the mainland.species to those found on the mainland.

Yet, these organisms were different from Yet, these organisms were different from island to island.island to island.

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Blue footed boobies Blue footed boobies (bobos ~ clown)(bobos ~ clown)

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Marine & land iguanasMarine & land iguanas

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Ahhh!!!Ahhh!!!

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Neck-size vs. Vegetation heightNeck-size vs. Vegetation height

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Galapagos’ FinchesGalapagos’ Finches

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Darwin’s Two Main PointsDarwin’s Two Main Points

Species of organisms living on Earth today descended Species of organisms living on Earth today descended from ancestral species. They spread in to different from ancestral species. They spread in to different habitats where they accumulated different modifications habitats where they accumulated different modifications (adaptations) to diverse ways of life. (Descent with (adaptations) to diverse ways of life. (Descent with modification)modification)

Natural Selection is the mechanisms for evolution. Natural Selection is the mechanisms for evolution. Natural selection is the process by which individuals with Natural selection is the process by which individuals with inherited characteristics well-suited to the environment inherited characteristics well-suited to the environment leave more offspring on average than do other leave more offspring on average than do other individuals.individuals.

• As time passes, populations change through time….they evolve!As time passes, populations change through time….they evolve!

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Summary of the Theory of EvolutionSummary of the Theory of Evolution

DNA is the blue-print for building DNA is the blue-print for building ALLALL living things on living things on planet Earth.planet Earth.

DNA sequences are changed by random mutations, DNA sequences are changed by random mutations, radiation, viruses, chemicals, sexual reproduction, radiation, viruses, chemicals, sexual reproduction, migration, geological events, etc.migration, geological events, etc.

As a result there is variation within populations of a As a result there is variation within populations of a species.species.

Those individuals of a particular species with a Those individuals of a particular species with a phenotype (phenotype (as a result of their genotypeas a result of their genotype) that is more fit ) that is more fit to survive in a given environment has a better chance to to survive in a given environment has a better chance to reproduce.reproduce.

Those individuals who reproduce Those individuals who reproduce moremore pass-on their pass-on their genes at a higher frequency than those who do not.genes at a higher frequency than those who do not.

Given enough time anything is possible!!! (Earth is 4.6 Given enough time anything is possible!!! (Earth is 4.6 billion years old)billion years old)

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The EndThe EndBring book tomorrow for a grade!!!Bring book tomorrow for a grade!!!