Descent with Modification: CHAPTER 22: What was the philosophical consensus during the 18 th and 19 th centuries regarding Natural History and Evolution? EVOLUTION: EVOLUTION HISTORY: 1. Georges Cuvier 2. James Hutton 3. Thomas Malthus 4. Jean Baptiste de Lamarck 5. Charles Lyell 6. Alfred Wallace EVOLUTION: Additional Scientists of importance: Carolus Linnaeus- taxonomy ( ) Gregor Mendel- Inheritance (1865) EVOLUTION Evolution? Natural Selection? Driving Force of Natural Selection? TWO MAIN POINTS THAT COME FROM DARWINS ON THE ORIGIN OF SPECIES 1. Organisms presently inhabiting the Earth are descendants of ancestral species that were different 2. Natural selection is the mechanism for this evolutionary process NATURAL SELECTION AND ADAPTATION: 5 observations from Ernest Mayer: 1. Exponential fertility 2. Stable population size 3. Limitation of resources 4. Varying Characteristics 5. Variation is inheritable NATURAL SELECTION AND ADAPTATION Three inferences (Ernest Mayer): 1. Struggle for Existence 2. Non-random survival 3. Natural selection-differential success in reproduction EVIDENCE FOR EVOLUTION: 1. Biogeography Geographical distribution of species Example: Island vs. Mainland- most island species are closely related to the nearest mainland or island EVIDENCE FOR EVOLUTION: The Fossil Record: Supported by Biochemistry, Molecular biology, Cell biology Evolutionary transitions leave fossil evidence EVIDENCE FOR EVOLUTION: Comparative anatomy: Anatomical Homologies Suggest common ancestor Molecular Homologies: Vestigial organs EVIDENCE FOR EVOLUTION: Comparative Embryology : pharyngeal pouches, embryonic tails EVIDENCE FOR EVOLUTION: Molecular Biology DNA, genes, proteins Common genetic code FINAL POINTS ABOUT EVOLUTION AND NATURAL SELECTION: 1. Individuals do NOT evolve A population is the smallest unit that can evolve Evolution is measured as changes in a population over a succession of generations FINAL POINTS ABOUT EVOLUTION AND NATURAL SELECTION: 2. Natural Selection can amplify or diminish only heritable traits No Lamarckian use/disuse No inherited acquired characteristics FINAL POINTS ABOUT EVOLUTION AND NATURAL SELECTION: 3. Natural selection is always in operation, BUT the environment determines the favorability of the trait Traits can be favorable or detrimental FINAL THOUGHT: According to Darwins view, natural selection is a purposeless process but an efficacious one.. David Quammen The Reluctant Mr. Darwin