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How did such tremendous diversity of life come to exist on this planet? PowerPoint PPT Presentation


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How did such tremendous diversity of life come to exist on this planet?. Evolution. Each organism is unrelated and is created independently Life evolved many times. All life shares common ancestry - all life is related Life evolved once only. What Did Darwin Do?. Two key things:

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How did such tremendous diversity of life come to exist on this planet?

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Thescienceteacher

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Thescienceteacher

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Thescienceteacher

How did such tremendous diversity of life come to exist on this planet?

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Evolution

Evolution

Each organism is unrelated and is created independently

Life evolved many times

All life shares common ancestry - all life is related

Life evolved once only

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What did darwin do

What Did Darwin Do?

Two key things:

1. He provided evidence for evolution

2. He proposed a theory to explain the mechanism by which evolution occurs

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Evolution1

Evolution

Darwin's definition: descent with modification.

,

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Darwin s evolution

Darwin’s Evolution

  • Organisms have changed overtime

  • All organisms share common ancestors

    3.Change is gradual

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1 fossil record change over time

1. Fossil Record – Change over time

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2. Shared Structures – Common Ancestry

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3. Similarities Between Embryos – Change is gradual

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The mechanism for evolution

The Mechanism for Evolution

Natural Selection

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Natural selection

Natural Selection

1. There is a "struggle" (metaphorically) to survive and reproduce (organisms produce potentially more offspring that can possibly survive)

2. Organisms show variation in characters that influence their success in this struggle for existence.

3. Parents possessing certain traits that enable them to survive and reproduce will contribute disproportionately to the offspring that make up the next generation.

4. The population in the next generation will consist of a higher proportion of individuals that possess whatever adaptation enabled their parents to survive and reproduce.

5. Overtime the population will become adapted to the environment

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Requirements for natural selection

Requirements for Natural Selection

  • 1. Heritable variation for some trait

  • 2.Differential survival and reproduction associated with the possession of that trait.

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Antibiotic resistance an example of modern day evolution by natural selection

Antibiotic resistance – an example of modern day evolution by natural selection

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Variation in population  over production of offspring  competition between offspring  best adapted survive and reproduce  favourable characteristics passed onto next generation

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Why haven’t polar bears got white noses?

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4 genetic changes

4. Genetic Changes

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Darwin s theory of evolution by natural selection

Darwin's Theory of Evolution by Natural Selection

  • Individual characteristics of an organism are vitally important for its ability to survive and to breed

  • Individuals of a given species vary in many characteristics

  • Individuals produce more offspring than can survive i.e. there is competition

  • Only a small proportion of offspring will therefore survive. If those characteristics which help the oranThese individals that survive

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Did humans evolve from chimpanzees

Did humans evolve from chimpanzees?

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Evidence for evolution

Evidence for Evolution

1.Fossil evidence shows the course of evolution through time

2. Similar structures are shared by many organisms

3. Comparative embryology (looking at similarities between developing embryos of different species)

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