A Short History

  Aristotle  Envisioned – scala naturae  Fixed species occupied allotted rungs on an increasingly complex ladder of life  Linnaeus –  Devised a hierarchy for classification  King Phillip Came Over For Grape Soda Pre-Darwinian View

  Cuvier –  Believed that catastrophic extinctions explained unique sets of fossil species between successive strata  James Hutton & Charles Lyell  Proposed that profound changes in the earth’s surface can result from slow, continuous actions Pre-Darwinian View

  Jean Baptiste Lemark  Inheritance of Acquired Characteristics  Proposed the theory of evolution where increasing complexity & more perfect adaptations result from inheritance of characteristics acquired by organisms interacting w/ the environment  However, there is NO evidence for inheritance of acquired characteristics Pre-Darwinian View

  Darwin  Proposed the idea that new species originate from ancestral forms by the gradual accumulations of adaptations  Alfred Wallace  Independently arrived at the theory of Natural Selection soon after Darwin Pre-Darwinian View

  Darwinian view of life has 2 parts:  Descent with Modification  Natural Selection Dual Meaning of Darwinism

  Survival of the Fittest  The driving force of Evolution  Based on differential success in reproduction  Individuals best adapted to the local environment leave more offspring = thereby pass on their adaptive characteristics more frequently Natural Selection

  Fact 1:  All species’ population size would increase exponentially if all individuals that are born reproduce successfully  Fact 2  Most populations are normally stable in size, except for seasonal fluctuations  Fact 3  Natural resources are limited 5 Facts of Nature

  Fact 4  Individuals of a population vary extensively in their characteristics; no 2 individuals are exactly alike  Fact 5  Much of this variation is inherited 5 Facts of Nature

  Darwin’s 1 st Inference/Conclusion:  Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, w/ only a fraction of offspring surviving each generation Darwin’s Conclusions

  2 nd Inference/Conclusion:  Survival is a struggle that depends on the inherited characteristics of the individual. Surviving individuals will produce more offspring  3 rd Inference/Conclusion:  Unequal ability to survive and reproduce will lead to gradual change in a population

  Biogeography of species  First suggested common descent – island species are more closely related than those on distant shores  Chronological fossil record  This supports and is compatible w/ other lines of evidence  Taxonomic hierarchy  reflects common descent Signs of Evolution

  Homologous structures  testify to an evolutionary remodeling process  Embryonic Development  Reveals homologies not apparent in adult species  Closely related species show unmistakable similarities in their DNA and Proteins Signs of Evolution Cont.

 Tree of Life - Cladogram