Evolution natural selection adaptation
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Evolution: Natural Selection & Adaptation. Chapters 15 and 16. Evolution is the Unifying Principle of all Biology forms foundation for all other concepts answers all “why” questions explains context of boil. phenomena two major aspects:

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Evolution: Natural Selection & Adaptation

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Evolution natural selection adaptation

Evolution:Natural Selection & Adaptation

Chapters 15 and 16


Evolution natural selection adaptation

  • Evolution is the Unifying Principle of all Biology

    • forms foundation for all other concepts

      • answers all “why” questions

      • explains context of boil. phenomena

    • two major aspects:

      • descent from a common ancestor  why org. have similar characteristics

      • adaptation to environment  explains diversity of life

  • Charles Darwin

    • developed theory of evolution

      • 1859: The Origin of Species

    • descent with modification

      • “change through time”

    • evol. occurs through natural selection

      • env. determines which ind. will survive and reproduce

        • are fittestind.  possess best adaptations

      • adaptations

        • characteristics that increase chance of survival and reproduction


Evolution natural selection adaptation

  • Natural Selection

    • mechanism of evol.

    • based on five key points:

      • ind. vary within pops.

      • some variation is inherited and affects survival

      • more offspring are produced than env. can support

      • offspring with most adaptive traits will survive better and produce more of their own offspring

        • offspring will also have the adaptive traits

      • over time, the pop. changes

        • more adaptive traits become more prevalent

    • environmental forces affect an individual’s phenotype

      • to survive, an org’s. phenotype must become adapted to env.

        • but, genotype determines phenotype

      • orgs. with most adaptive genotypes survive better and pass their genes onto their offspring

        • their genotypes produce a more fit and adaptive phenotype

          • such organisms are “selected for”

      • variation in pop.  small genetic changes  produce new genotypes  lead to new, better adapted phenotypes

      • continued phenotypic change  development of new species


Evolution natural selection adaptation

  • variation

    • occurs in pops. in many different traits

      • behavioral, biochemical, physical

      • must be genetically based

      • two primary sources

        • mutation

          • source of new variations

        • crossing over

          • source of new combinations of traits

      • is very beneficial to a pop. evol. cannot occur without it

    • maintained through a wide variety of mechanisms

      • dispersal of young

      • masking recessive alleles

      • heterozygote advantage

      • others

Fig. 15.7 Variation in a human population


Evolution natural selection adaptation

Fig. 16.16 An example of heterozygote advantage


Evolution natural selection adaptation

  • Modern Synthesis – Today’s Theory of Evolution

    • incorporates genetics into evolution

  • nat. sel. causes populations to change, not individuals

  • selection is not a random process

  • evol. is not based on the needs of organisms

    • mutations  acted on by nat. sel.  adaptation to local env. conditions

  • selection has been tested and confirmed many times in many organisms

  • fittest ind. are those more likely to survive, based on adaptations

    • evolution is not “survival of the fittest”

    • survival not as important as reproduction

  • Fig. 16.3

    Natural selection in peppered moths


    Evolution natural selection adaptation

    • Evidence and Examples of Evolution

      • fossil record

        • radioactive dating

        • hard-bodied vs. soft-bodied organisms

        • phylogenetic trees

    Fig. 17.17 Evolutionary history of Equus


    Evolution natural selection adaptation

    Fig. 30.7 Human evolution


    Evolution natural selection adaptation

    • biogeography

      • study of where organisms are found on earth

      • provides evidence of past evol. history

      • isolated regions have their own types of plants and animals

      • similarity of unrelated species in similar environments

    Page 274 Biogeographical regions

    Fig. 15.5 An example of evidence through biogeography – the European hare and the Patagonian (S.A.) hare


    Evolution natural selection adaptation

    Fig. 15.14 Biogeography. Some mammals of Australia and their North and South American counterparts.


    Evolution natural selection adaptation

    • comparative anatomy

      • homologous vs. analogous structures

      • adult and embryological evidence

      • transitional organisms

      • vestigial structures

    Fig. 15.16 Developmental homologies

    Fig. 15.15 Homologous structures


    Evolution natural selection adaptation

    Fig. 15.13 Ambulocetus – an ancestor of whales and a transitional fossil

    Fig. 15.12 Transitional fossils - Archaeopteryx


    Evolution natural selection adaptation

    Some vestigial structures

    Fig. 17.1 Whale evolution, showing transitional organisms


    Evolution natural selection adaptation

    • molecular biology

      • genetic code and cellular structure

      • DNA and amino acid similarities

      • number of mutations

      • phylogenetic trees

    Fig. 15.17 Biochemical differences – evidence from molecular biology


    Evolution natural selection adaptation

    • artificial selection

      • selective breeding

    Fig. 15.9 Artificial selection in plants

    Fig. 15.8 Artificial selection in animals


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