Chapter 22: Descent With Modification A Darwinian View of Life On the Origin of Species by Means of Natural Selection by Charles Darwin  Attempts to create a family tree for all life on Earth Mechanism= natural selection Mechanism= natural selection

Groundwork for Darwin’s Theory Taxonomy Taxonomy Linnaeus- group organisms based on similar structures Linnaeus- group organisms based on similar structures Paleontology Paleontology Cuvier Cuvier Study of fossils Study of fossils Gradualism Gradualism Change is slow but continuous Change is slow but continuous Lamarck’s Theory Lamarck’s Theory First to include gradualism First to include gradualism Use & disuse Use & disuse Inheritance of acquired characteristics Inheritance of acquired characteristics

Natural Selection Population CAN change over generations if individuals with better adaptations leave more offspring Population CAN change over generations if individuals with better adaptations leave more offspring Evolutionary adaptation Evolutionary adaptation Inherited characteristics that enable survival and reproduction in a certain environment Inherited characteristics that enable survival and reproduction in a certain environment Evolution Evolution Change in genetic composition of a population over time Change in genetic composition of a population over time Descent with modification (Darwin’s term) Descent with modification (Darwin’s term) All organisms are related through descent with an ancestral organism All organisms are related through descent with an ancestral organism Modifications in species a result of inhabiting different environments Modifications in species a result of inhabiting different environments

Natural selection Requirements Requirements Resources are limited Struggle for existence Struggle for existence Individuals with heritable traits better suited to environment leave more offspring Individuals with heritable traits better suited to environment leave more offspring Population gradually evolves to exhibit higher number of individuals with beneficial trait Population gradually evolves to exhibit higher number of individuals with beneficial trait

Natural Selection INDIVIDUALS DO NOT EVOLVE- POPULATIONS CAN!!!! INDIVIDUALS DO NOT EVOLVE- POPULATIONS CAN!!!! Environment determines which traits are favored Environment determines which traits are favored Biogeography- similarities found among species in similar ecological niches Biogeography- similarities found among species in similar ecological niches Convergence- unrelated species in similar niches have similar adaptations Convergence- unrelated species in similar niches have similar adaptations Divergence- related species in different ecological niches have dissimilar adaptations Divergence- related species in different ecological niches have dissimilar adaptations Environment does not create change- it selects for individuals who already possess beneficial adaptation Environment does not create change- it selects for individuals who already possess beneficial adaptation

Examples of natural selection at work Guppy sexual maturation age & predatory pressure Guppy sexual maturation age & predatory pressure Drug resistant HIV Drug resistant HIV Insecticide resistance in insects Insecticide resistance in insects

Evidence Fossil record Fossil record Homology Homology related species have similar underlying traits that MAY be used for different functions related species have similar underlying traits that MAY be used for different functions Homologous structures Homologous structures Comparative embryology Comparative embryology Vestigial structures (remnant structures) Vestigial structures (remnant structures) Molecular similarities (DNA, protein) Molecular similarities (DNA, protein)