9 30 16 BASIS OF BIOLOGICAL VARIATION Divinity Catastrophism and Evolution Divine Creation o Through the 14th century the Genesis version of Divine creation accepted as explanation for biological diversity o Included following beliefs Earth was young Archbishop Usher 10 22 4004 BC Species were unchanging fixity of species Species arranged in hierarchy with humans at the top Great Chain of Being o Challenges to Doctrine Discovery of New World and circumnavigation of glove exposed Europeans to diversity never before seen In 1514 Copernicus challenged Aristotle s notion that the Earth was fixed at center of the universe later elaborated by Galileo Other discoveries in physics and biology suggested that phenomena were governed by natural laws e g gravity Through the 18th century most still attributed creation to Divine forces but now phenomena were investigated not accepted as unknowable Making Sense of Biological Variation o Carolus Linnaeus 1707 1778 By 16th century interest in biological diversity was great Linnaean classification system formed the basis for taxonomy still used today With some controversy Linnaeus included humans in his scheme First to propose a process of biological change o Jean Baptiste Lamarck 1744 1829 Hypothesized a dynamic interplay between organic forms and the environment As environment changed organic forms changed due to increased or decreased use These acquired traits would then be passed on to offspring Catastrophism o Georges Cuvier 1769 1832 Opposition to Lamarck came to Cuvier who believed in the fixity of species Suggested that extinction in fossil record came as a result of regional catastrophes such as the biblical flood Locations of catastrophe were then repopulated from nearby unaffected regions The Darwinian Breakthrough o Charles Darwin 1809 1882 In 1831 Charles Darwin set sail on a 5 year global expedition aboard the H M S Beagle He left believing in the fixity of species and shortly later grew doubtful o Influencing Darwin s Thinking Charles Lyell 1797 1875 Principal of uniformitarianism if gravity is around now it has always been around Implied slow gradual change not catastrophism Required deep geological time Thomas Malthus 1766 1834 Essay on the Principle of Population Populations increase faster than the rate of resources Life is full of competition a struggle to survive Darwinian Natural Selection Variation exists in a given population species 2 Under given set of environmental conditions certain members possess traits that allow them to survive and reproduce more often than those lacking such traits some selected for others against With each generation population evolves adapts To Darwin evolution was simply descent with modification it had no particular direction no purpose 3