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Charles Darwin Was Darwin the First? Darwin was not the first to present the concept of evolution Word first appeared in 1647 Ancient Greeks inferred that species had descended from a common ancestor Darwin referred to evolution as “descent with modification”

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Was Darwin the First?

  • Darwin was not the first to present the concept of evolution

  • Word first appeared in 1647

  • Ancient Greeks inferred that species had descended from a common ancestor

  • Darwin referred to evolution as “descent with modification”

  • Explained it as the differential survival of organisms following their naturally occurring genetic variation

    • Natural Selection


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Early Influences on Darwin

  • Charles Lyell – geologist

  • Proposed that plant and animal species had arisen, developed variations over time and then became extinct

  • Also believed that earth’s physical landscape had changed over time

  • Thomas Malthus – proposed that populations outgrew their food supplies, causing competition between organisms and a struggle for one species to survive against another

  • Applied theory to humans, Darwin applied to all animal species


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Galapagos Islands

  • Darwin’s trip on the Beagle stopped in the Galapagos

  • Contained endemic species, not found anywhere else on earth

  • The species there looked similar to mainland species

  • But somehow specialized to their particular environment

    • proposed that changes were dependent on the environment


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Sequence

  • 1st: Adaptations  traits occur within organisms and allow them to be more successful in the environment

  • Darwin reasoned that the importance of these adaptations was to insure the survival of reproduction of the species

  • Successful adaptations help organisms to both survive and reproduce, so these adaptations are passed on to future generations

  • Natural Selection is the mechanism that explains how changes occur within a population with favorable variations for that particular environment surviving, reproducing and passing these variations on to the next generation

    • (environments are constantly changing)


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Sequence

  • 2nd Speciation – organisms on the Galapagos Islands had become geographically separated from one another

  • Produced reproductive isolation so that there is no interbreeding between organisms of same species

    • separates the gene pools of the populations

  • Darwin theorized that within a populations of species, adaptations would arise because of reproductive isolation and would develop adaptations specific to their particular environment over time

  • Eventually this would lead to new species evolving on the different islands

    • Which is what was observed


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Reproductive Isolation

  • All begins when a group becomes reproductively isolated from the rest

  • May be geographic, temporal or behavioral

    • It is most obvious in distant islands, such as the Galapagos or Hawaiian island

    • Mountains, rivers, lakes and other natural barriers can also geographically separate populations that once belonged to the same species


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Types of Reproductive Isolations

  • Temporal isolation occurs when there is a time difference between two species

    • Such as one species of flower opening up for pollination in the morning and another at night

  • Behavorial isolation occurs when the behavior of one species does not match another

    • One mating song for one bird is not recognized by another

  • Geographic isolation is the most common method of separating two populations of a species

    • Depends on the animal involved as to what is needed to separate it


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Finches

  • Classic example of speciation is the 13 species of finches on the Galapagos Islands

  • Each species, descended with modifications, from an ancestral species

  • Today, the different species of finches on the island have distinct habitats, diets and behaviors depending on the current climate conditions

    • Which determines what food is available to the birds


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Darwin’s Book

  • The Origin of Species – Presents Darwin’s theory (1859)

  • Has undergone modification and expansion and is now supported by studies in genetics and molecular biology


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