theories for evolution

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Theories for Evolution. Mr. Young. Evolution. The process of change within a living system over a period of time Genotype changes vs. Phenotype changes Micro vs. Macro Evolution Many different scientists have proposed theories about this process….…. Microevolution : - PowerPoint PPT Presentation


  • Theories for Evolution

    Mr. Young

  • EvolutionThe process of change within a living system over a period of timeGenotype changes vs. Phenotype changesMicro vs. Macro EvolutionMany different scientists have proposed theories about this process.

  • Microevolution: Small-scale evolutionary changes, usually on the molecular level, that occur over the span of a few generations and can therefore be detected in living populations.

  • Macroevolution: Large scale evolutionary changes, speciation events, that may require many hundreds of generations and are usually only detectable in the fossil record

  • Natural Selection: The differential reproductive success of certain phenotypes within a given environmentSurvival of the Fittest

  • Jean Lamarck1744-1829

    Acquired Traits

    Theory of use and disuse If an organ is used , it becomes stronger and better developedIf an organ is not used, it becomes weaker and withers away

  • LamarckAn organism acquires traits from its experience (not genes) and those traits are passed down, or inherited by their offspringExample: Lamarck believed that giraffes stretched their necks to reach food. Their offspring and later generations inherited the resulting long necks.

  • To Lamarck this meansIf you have a nose job, your kids will inherit the new nose!

    In real life, what nose will your kids get? (the old one or the new one?)

    Answer: the old one!

  • Is this logical?What determines that traits are passed to their children?DNA

    If you change your appearance, will your children inherit the new appearance

    No, because your DNA did not change

  • Natural SelectionEnvironmental SelectionRole of the EnvironmentAcquired traits???? (Lamarck)

  • Whos Your Daddy?Charles Darwin

    Theory-descent w/ modificationTheory-natural selection-main principles:

  • Charles Darwin1809 - 1882A naturalist (studied and preserved biological specimens that he collected)5 year voyage around the world aboard the HMS Beagle

  • Charles DarwinTheory of evolution by natural selectionNature will select the organisms that have variations that allow them to better survive (survival of the fittest) Descent by ModificationDarwin collected different species that were very similar and hypothesized that they shared a common ancestor

  • insects


  • Darwins Book: Origin of Species by Natural SelectionDescribed his theory of evolutionCaused a lot of controversy and angered the churchThe church initially believed that evolution is a sin against GodBefore Darwin died, the church accepted his theory and he was buried in a famous church in England

  • Charles DarwinDarwins theories are accepted today as the most accurate explanation for evolution

  • Darwin explains why giraffes have longer necks than their ancestorsOverproduction too many giraffesStruggle or compete for foodVariation in length of neck exists naturallyLonger neckreach food...surviveLonger necked giraffes survive and reproduce to eventually originate a new species of giraffes

  • Hugo De VriesAdded the concept that mutations in DNA are what cause organisms to change or have variationsEvolution is changes in DNA that is then inherited(microevolution)

  • Variations in organismsEach species has organisms with varying characteristics for example:some are tallersome have bigger feetsome run fastersome have better visionsome smell better

  • Struggle for existenceOverproduction of a species causes competition for resources to survive food water shelter space

  • Survival of the fittest by means of natural selectionVariations may give certain organisms advantages to survive, while other organisms diedNature selects those organisms that will die or survive

  • Evidence for Darwin's theoryFossil recordBiogeographyComparative AnatomyEmbryologyBiochemistry

  • Evidence for EvolutionHomologous structuresSimilar shapeDifferent functionShared originExample: arms of human, wings of bats, wings of penguins, arms of alligatorsDivergent evolution

  • Evidence for EvolutionAnalogous structuresDifferent shapeSimilar function Different originsExample: wings of a humming bird and wings of a moth, both allow the organism to hoverConvergent evolution

  • Vestigial StructuresA structure that had a use in an ancestor but has no use in a particular organismExamples: Appendix in humansTail bones in humans we have no tailsTiny leg bones in snakesthey have no legsWings in penguinsthey do not flyNipples on boysthey do not produce milk

  • Embryology

    The study of an organism from creation to birthEmbryos have tails that vanish into their spinesgill slits, like fish to breath that vanish into earscoats of hair that fall off at birth

  • Embryos go through stages of heart development2 chambers like fish hearts3 chambers like reptiles4 chambers like birds and mammals

  • AdaptationsA trait that increases an organisms chances of survival

  • What forces cause evolution?MutationMigration (gene flow)Genetic driftRandom eventsSmall populationsNon-random matingNatural selection-4 types;

  • Types of natural selectionStabilizingDirectionalDisruptiveAka diversifyingsexual

  • Natural Selection?

    What leads to these changes?Random mutationsOrganisms w/ shorter generation times have higher mutation rates & so evolve quicker than animals w/ longer generation timesExamples:Industrial Revolution vs. Peppered Moth

  • Natural selection results from Selection Pressuresthose aspects of the environment that can have a notable impact on the reproduction of members of a particular species over evolutionary time. adaptations

  • Defense MechanismDifferent ways for organisms to defend themselvesExample: thorns on rose bush

  • MimicryCopying the appearance of another, more dangerous specieExample, the fat bumble bees do not sting, but they copy the yellow/black appearance of thin bumble bees that do sting

  • CamouflageThe ability of an organism to blend into their environmentExample, fish have pale bottoms and dark topsFrogs are shades of green

  • Lets play name that adaptation!!!


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