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Transcript
Ch. 22 Descent with Modification: A Darwinian View of Life View of life • Before Darwin: • Plato: » Two worlds, real (ideal/eternal) and illusory (imperfect) » Evolution counterproductive • Aristole: scala naturae » No evolution, permanent. • Natural Theology: » Nonevolving, Creator’s plan, creator’s purpose/design • Carolus Linaeus: Taxonomy, no evolutionary kinship Fossils, Paleontology •Sedimentary Rocks/fossils, strata, erosion, organism succession • Georges Cuvier: catastrophism (Paleontology) •James Hutton: gradualism/mechanisms, current •Charles Lyell: uniformarianism geological processes Lamarck Two Concepts used: •Use/Disuse •Inheritance of acquired characteristics •Adaptation to the Environment: Primary product of evolution •Sentiments interieurs or “felt needs” Darwinian Revolution (1809-1882) •University of Edinburgh (medicine) •Christ College at Cambridge (clergyman) •Natural theology •22 yrs. Old sailed on HMS Beagle •Chart South American coastline •Studied plants and animals •Galapagos •Returned 1836 •Used Lyell and Lamarck studies Figure 22.5 The Voyage of HMS Beagle What was his reasoning? • The voyage of the Beagle • Galapagos islands • Darwin focused on adaptation – descent with modification – observations What’s the reason for diversity and numerous similarities among species? • On the Origin of Species by Means of Natural Selection. 1859. Charles Darwin. • In his book, Charles Darwin made 2 major points: – 1. Species evolve from ancestral species and were not specially created. – 2. Natural selection is the mechanism that could result in this evolutionary change. •Branching history •Most branches extinct (99%) Figure 22.7 Descent with modification Observation #1 • All species have such great potential fertility that their population size would increase exponentially if all individuals that were born reproduced successfully. Observation #2 • Populations tend to remain stable in size, except for seasonal fluctuations. Observation #3 • Environmental resources are limited. • Inference #1 – Production of more individuals that the environment can support leads to a struggle for existence, with only a fraction of offspring surviving. Observation #4 • Individuals of a population vary extensively in their characteristics/ no two individuals are exactly alike. Observation #5 • Much of this variation is heritable. Inference #2 – Survival is not random, but depends in part on the hereditary constitution of the surviving individuals. Those individuals whose inherited characteristics fit them best to their environment are likely to leave more offspring than less fit individuals. Inference #3 – This unequal ability to survive and reproduce will lead to a gradual change in a population. Summary of Darwin’s Ideas • Natural selection: differential success in reproduction. • Natural selection occurs from the interaction between the environment and the inherent variability in a population. • Variations in a population arise by chance, but natural selection is not a chance phenomenon. • Artificial Selection: breeding of plants and animals. Example of Natural Selection • Ground Finches – avg. beak depth (inherited trait) oscillates with rainfall. • Wet years - feed on small seeds - avg. beak depth decreases. • Dry years - small seeds less plentiful, survival depends on the finches being able to crack the less preferred larger seeds. Avg. beak depth increases. • What does this study indicate? What does this study indicate? • Natural selection is situational. What works in one environment may not work in another. • The environment did not create beaks specialized for large or small seeds, but only acted on inherited variations already present in the population. Current evidence of Natural Selection Figure 22.12 Evolution of insecticide resistance in insect populations Figure 22.13 Evolution of drug resistance in HIV Evidence for Evolution • Homology • Anatomical • Vestigial • Embryonic • Molecular • Biogeography • endemic • Fossil record • Drosophila fossils in Hawaii Theoretical about Evolution??? Theories are attempts to explain facts and integrate them with overreaching concepts. Natural Selection is the proposed mechanism of Darwin’s Theory of Evolution Theories are more than a simple hypothesis. Predictions stand up with continuous testing by experiments and observations “There is grandeur in this view of life”