_Unit_7_Natural_Selection___Chp_22

• Pre-Darwin (everyone thought no evolution)

  • Plato- Organisms are already perfectly adapted in thier environments

  • Aristotle- organisms arranged on a “scale of life” from simple to complex

  • Creationism- ultimate being created the universe

  • Created viewpoint that all species could be identified and named (taxonomy)

  • major factor in the Linnaeus classification system

  • Cuvier- catastrophism

    • fossils wer the remains of species lost due to catastrophe

    • no new species were originated, species could only be lost over time

  • Hutton- Gradualism

    • changes on the Earth were gradual, not catastrophic

  • Lyell- uniformitarianism

    • earth must be very old, idea that slow and subtle process can cause substantial change

  • Lamarck-

    • Life did change from simple to complex

    • fossils were remains of lost organisms

    • (bad idea) use and disuse

      • body parts used to survive become larger and stronger

      • body parts not used to survive are thrown away

    • (good idea) Acquired Characteristics

      • modifications acquires by use/disuse were passed onto offspring

• Natural Selection- observable phenomenon

  • first described by Charles Darwin

  • organisms that are well adapted to their environment are most likely to survive and reproduce

  • genes that have adaptive traits will increase in frequency in the next generation

• Charles Darwin

  • father of modern theory on evolution

  • Specific theory called Descent with Modifcation

  • Do not say survival of the fittest

  • published The Origin of Species in 1859

• contributing factors to natural selection

  • overproduction-the likelihod of living things to produce more offspring than the environment can support

  • variation-offpsinrg will posses natural genetic differences which may increase their survival and reproduction

  • competition- organiss will die for limited environmental resources and those better suited to acquire them will surivive and reproduce more often

  • differntial reproductive success: organisms with adaptive variations will outcompete other individuals and reproduce more often- passing adaptive alleles onto the next generation more frequently

• Evolutionary fitness

  • measured by reproductive success

  • organisms that survive and pass on their genes to the next generation are considered fit

  • organisms that do not pass on their genes to the next generation are not fit

• a popuplation is a group of members of the same species capable of interbreeding and producing fertile offspring

• a gene pool consists of all of the alleles for all loci in a population

• Natural Selection

  • biotic and abiotic factors in the environment may change or be stable

    • biotic- ecological factors imposed in an ecosystem by living things ex) predation, competition

    • abiotic- ecological factors imlosed in an ecosystem by nonliving things ex) sunlight, pH

• Selection pressures

  • environmental forces that affect an individuals reproductive success

  • organisms lacking adaptive variations will have lowwer reproductive rates

  • as environments change, formerly adaptive phenotypes may lose theiir adaptive value

  • if allele frequencies change from one generation to the next, the population is deemed to be evolving

• Types of Natural Selection

  • Directional Selection: one ened of the phenotype spectrum is selected for

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  • Disruptive selection: both ends of the phenotypic spectrum are selected for

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  • stabilizing selection: both ends of the phenotypic spectrum are selected against

• natural selection in huimans

  • sickle cell anemia in human is under the control of two alleles at a single locus

  • wildt type aeenenffifssdc nad sickle cell ldads tp assms

• concvergnet evolution

  • evoltuion of similar or analhous featr=ure in didftjatoe=kates species

  • evidence of evolution\

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    • evidence of evolutiin

    • FOSRIII KRECORD

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    • sedimentary rock atrad reveal relative age of a tock

    • key tawkwars wsiht fofisl

    • ot has chainged

    • mayb sepcies fail to survive

    • focopooiaation as a arare event only hard [wrts torassa;zoe well, problem in infin re

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    • domains of life

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    • jniversal of cahhdrhahrhacteram

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embyology

• Biogeography

  • geographjic distribution of species, provides evidence of evolution

  • earth’s continenets were formerly united in a single large continent called Pangea, but since hace separated by continental drift

  • an understanding of continent movement and modern distribution of species allows us to predict when and where different groups evolved