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Descent w/ Modification Chapter 22 Lecture Objectives 1. Charlies Darwin – Before & After 2. Descent w/ Modification & Natural Selection 3. Evidence for Evolution CHARLES DARWIN AND THE ORIGIN OF SPECIES Biology came of age on November 24, 1859. Charles Darwin published On the Origin of Species by Means of Natural Selection, an assemblage of facts about the natural world. © 2013 Pearson Education, Inc. Historical context of Darwin’s ideas Common beliefs Who created living organisms? Did they evolve? What was the age of the earth? Did the earth change? 1809 Lamarck publishes his hypothesis of evolution. 1798 Malthus publishes “Essay on the Principle of Population.” 1795 Hutton proposes his principle of gradualism. 1812 Cuvier publishes his extensive studies of vertebrate fossils. 1830 Lyell publishes Principles of Geology. Sketch of a flying frog by Wallace 1858 While studying species in the Malay Archipelago, Wallace (shown above in 1848) sends Darwin his hypothesis of natural selection. 1790 1870 1809 Charles Darwin is born. 1831–1836 Darwin travels around the world on HMS Beagle. Marine iguana in the Galápagos Islands Figure 22.2 1859 On the Origin of Species is published. 1844 Darwin writes his essay on descent with modification. Darwin in 1840, after his return from the voyage HMS Beagle in port Great Britain NORTH AMERICA EUROPE ATLANTIC OCEAN The Galápagos Islands Genovesa Marchena Santiago Fernandina Isabela 0 20 40 AFRICA PACIFIC OCEAN Pinta SOUTH AMERICA Equator Daphne Islands Pinzón Santa Santa Cruz Fe Florenza Kilometers Figure 22.5 San Cristobal Chile PACIFIC OCEAN Equator Brazil Cape of Good Hope Argentina Española Cape Horn Malay Archipelago PACIFIC OCEAN AUSTRALIA Tasmania New Zealand The Grand Canyon (a) Charles Darwin and (b) Alfred Wallace wrote scientific papers on natural selection that were presented together before the Linnean Society in 1858. CHARLES DARWIN’S UNEXPECTED PATTERNS 1. Was it possible for a species to diverge from the original population? 2. Similarity between fossils of extinct & extant species occurred at every location © 2013 Pearson Education, Inc. (a) Cactus-eater Figure 22.6 (b) Insect-eater (c) Seed-eater CHARLES DARWIN’S UNEXPECTED PATTERNS CON’T. Glyptodont Hairy Armadillo © 2013 Pearson Education, Inc. Darwin’s Two Main Points in The Origin of Species 1. Descent with Modification Organisms inhabiting Earth today descended from ancestral species. - As organisms spread over various habitats, they are modified or changed by accumulating adaptations to diverse ways of life - AKA evolution: a change in the genetic composition of a population over time. © 2013 Pearson Education, Inc. Darwin’s Two Main Points in The Origin of Species con’t. 2. Natural Selection is the mechanism for descent with modification Process in which organisms with certain inherited characteristics are more likely to survive and reproduce than are individuals with other characteristics. Populations change over generations. Natural selection thus leads to evolution. Darwinian Fitness: measure of viable offspring compared to other members of that species © 2013 Pearson Education, Inc. EVIDENCE OF EVOLUTION Evolution leaves observable signs. We will examine five of the many lines of evidence in support of evolution: 1. the fossil record, 2. biogeography, 3. comparative anatomy, 4. comparative embryology, and 5. molecular biology. © 2013 Pearson Education, Inc. Australia Common ringtail possum Koala Common wombat Red kangaroo Humerus Radius Ulna Carpals Metacarpals Phalanges Human Figure 22.15 Cat Whale Bat Pharyngeal arches Post-anal tail Chick embryo (LM) Figure 22.16 Human embryo Primate Percent of selected DNA sequences that match a chimpanzee’s DNA 92% Chimpanzee Human Gorilla Orangutan Gibbon Old World monkey 96% 100% Support for Natural Selection according to Darwin 1. All species tend to produce excessive offspring 2. Organisms vary heritable. Fig. 22.10 © 2013 Pearson Education, Inc. Fig. 22.11 Natural Selection in Action Today Examples of natural selection include pesticide-resistant insects, antibiotic-resistant bacteria, and drug-resistant strains of HIV. © 2013 Pearson Education, Inc. Evolved Beliefs after On the Origin of Species Organisms can change over time. Some organisms have gone extinct. Earth is ~ 4.5 billion years old The geology of the earth is not constant, but always changing. Organisms descend from ancestral species.