Evolution Chapter 2
Evolution Chapter 2 BIOL 3303
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This 12 page Class Notes was uploaded by Madeline Abuelafiya on Saturday January 30, 2016. The Class Notes belongs to BIOL 3303 at Southern Methodist University taught by Dr. John Wise in Winter 2016. Since its upload, it has received 22 views. For similar materials see Evolution in Biology at Southern Methodist University.
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Date Created: 01/30/16
Chapter 2 Biology: from natural philosophy to Darwin Darwin’s insights form the foundation of evolutionary theory • Explains how patterns of diversity came to be • Combined his ideas with work of many others Early naturalists classified life’s diversity Carl Linnaeus (1707-78): Father of modern taxonomy Some recognized record of historical change Nicolas Steno (1638-86): Father of geology and stratigraphy Early ideas about evolution • Earth formed according to laws of physics and chemistry – Older than previously thought • Life emerged as distinct types – Transformed when environment changed Georges Buffon (1707-88) Paleontology provided evidence that life changed • Georges Cuvier (1769-1832) – Fossils resemble but are not exactly the same as modern species – Many past species are extinct – In 1801 Cuvier published a list of 23 species that no longer existed Cuvier‘s Fossil Evidence of Extinction • The Irish Elk • Hard to overlook... http://www.prehistoric- wildlife.com/species/m/megaloceros.html Megaloceros giganteus Geologists recognized that change was gradual • James Hutton – Observable processes produce small changes that accumulate over time – The earth must be very, very old • far older than the 6000 years J(1726-1797) assigned by theologians from biblical inference. • William Smith – Different rock layers contain distinct fossils William Smith (1769-1839) Smith created first geological map 5 Geologists named rock formations from different periods Sedimentary formations often identified by types of fossils they contain Evolution as striving • Life driven from simple to complex – thought that he saw several lines of descent in collected fossils and current species – Each was a chronological series of older to younger fossils leading tJean-Baptiste Lamarck modern species (1744-1829) • Adaptation occurs through inheritance of acquired changes – False Charles Darwin (1809-1882) • Medical school in Edinburgh – Dropped out Preferred to study nature • Trained to become clergyman at Cambridge • Invited to serve as unofficial naturalist for HMS Beagle in 1831 Voyage of the Beagle • Collected many fossils and living organisms • Studied geology while reading Principles of Geology by Lyell – Uniformitarianism: observable natural processes responsible for events in the past – Saw seashells on a mountain top in South America – Witnessed an earthquake that raised the ground significantly Observations convinced Darwin that life evolved After decades of waiting Prompted to go public • Letter from Alfred Russel Wallace proposed similar evolutionary ideas – Common ancestry – Natural selection • Compromise publishing arrangement set up by Geologist Lyell • Letters from Darwin and Wallace presented at Alfred Russel Wallace Linnean Society in 1858 (1823-1813) • The Society members were “underwhelmed” Darwin’s book published in 1859 • On the Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life Evolution by natural selection (1) Species are related by descent with modification from a common ancestor (2) Species change through time (3) Changes occur through natural selection 460 pages of “one long argument” Common descent makes sense of puzzling patterns in nature Homologous trait: similar because of inheritance from a common ancestor Common descent makes sense of puzzling patterns in nature Fish vascular anatomy for gills adapted in development for lungs of reptiles/mammals Evolution isn’t intelligent – it is imperfect Recurrent laryngeal nerve – One of the cranial nerves – Goes from the brain through a tube near the heart to the larynx. • Direct route in fish. • Detour of ~ 1-2 feet in humans. • 10 to 15 feet of extra nerve in giraffes. Why? Because evolution and natural selection operates in the short term, with each step taking place as a modification of what is already present. The giraffe is cobbled together from what came before. William Clift's Law of Succession Fossil and modern organisms are related in each area • Important because it connects life forms from one time to another in the same place (required by Theory of Evolution). Huge effect on Darwin in South America • Darwin: Armadillos of Argentina (top, modern pygmy armadillos and fossil nd glyptodont (2 from top) are related. • Richard Owen: extinct Australian mammal Diprotodon (bottom) related to wombat marsupial (2 ndfrom bottom). Reproductive Potential - In every population studied, more offspring are produced than survive to breed. Also known as biotic potential or fecundity. The number of progeny an organism or pair can produce under optimal conditions assuming no deaths in the offspring. In every population looked at, some individuals are more successful at mating and producing offspring than others. In a steady state population (no growth and no decline) an average of 1 offspring per breeding survivor is produced. Postulate that Individuals vary in survival and reproduction is universally true. 11 Natural selection: Darwin’s mechanism of change Overall effect of Natural Selection: On average, surviving individuals / populations will have higher fitness than those that do not survive Leads to Adaptations: traits that have evolved by natural selection Darwin’s theory remains the best explanation for the diversity of life • Natural selection and sexual selection are powerful forces in natural populations • Darwin’s theory has also been expanded – Genetic drift: random changes to the gene pool resulting from chance events – Sexual selection – Kin selection – Group selection (?)
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