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What Best Explains Diversity? I. Special Creation Aristotle to Darwin ~350 BC to 1800s II. Evolution Darwin to Present (A) Each organism originated independently. (A) All organisms originated from common ancestors. (B) Since the time of creation, each organism has remained the same. (B) Organisms have and continue to change over time. (C) All organisms were created recently. (C) Evolution of organisms began 3.7 billion years ago For a more details concerning the History of Evolutionary Thought: http://www.ucmp.berkeley.edu/history/evolution.html For information about the Evolution/Creationist Controversy: http://www.talkorigins.org/ National Center for Science Education: http://www.natcenscied.org/ The Important Players that Influenced Charles Darwin John Ray (1628-1705) : Practiced “Natural Theology”; he thought that god’s creation can best be understood and appreciated through study of nature. Carl Linnaeus (1707-1778): Father of taxonomy; authored Systeme Naturae. Also practiced natural theology. Georges-Louis Leclerc, Comte de Buffon (1707-1788) : 1) Questioned the idea of Special Creation. Wrote about the similarity of man and apes in Historie Naturelle. 2) Questioned the idea of a young earth in Les Epoques of Nature. Erasmus Darwin (1731-1802): Great intellectual of 18th century Organic life beneath the shoreless waves Was born and nurs'd in ocean's pearly caves; First forms minute, unseen by spheric glass, Move on the mud, or pierce the watery mass; These, as successive generations bloom, New powers acquire and larger limbs assume; Whence countless groups of vegetation spring, And breathing realms of fin and feet and wing. The Temple of Nature William Paley (1743-1805): wrote: Natural Theology: or, Evidences of the Existence and Attributes of the Deity, Collected from the Appearances of Nature. . . . when we come to inspect the watch, we perceive. . . that its several parts are framed and put together for a purpose, e.g. that they are so formed and adjusted as to produce motion, and that motion so regulated as to point out the hour of the day; that if the different parts had been differently shaped from what they are, or placed after any other manner or in any other order than that in which they are placed, either no motion at all would have been carried on in the machine, or none which would have answered the use that is now served by it. . . . the inference we think is inevitable, that the watch must have had a maker -- that there must have existed, at some time and at some place or other, an artificer or artificers who formed it for the purpose which we find it actually to answer, who comprehended its construction and designed its use. Thought that only an Intelligent Designer could have made life. Age of Comparative Anatomy Georges Cuvier (1769-1832): Founded vertebrate paleontology and developed the comparative method of organismal biology. Established extinction as fact. Geoffroy St. Hilaire (1772-1844): Geoffroy spent much time drawing up rules for deciding when structures in two different organisms were variants of the same type. One of his more infamous theories was that the segmented external skeleton and jointed legs of insects were equivalent to the internal vertebrae and ribs of vertebrates; insects literally live inside their own vertebrae and walk on their ribs. He is said to have stated, "There is, philosophically speaking, only a single animal." Richard Owen (1804-1892): Defined homology in 1843 as "the same organ in different animals under every variety of form and function." Jean-Baptiste de Lamarck (1744-1829) First Theory of Evolution Transformational Evolution Humans Mammals Amphibians Scale Of Nature Fish Insects Jellyfish Zooplankton Pond Scum Time Lamarck : • Believed in inheritance of acquired characteristics (acquired during life) Parents Parents Change During Lifetime Change Inherited by Offspring Parents Change During Lifetime Change Inherited by Offspring Parents Change During Lifetime Grows up Among Short Trees Inheritance of Acquired Characteristics Two Sibling Giraffe’s Grows up Among Tall Trees: Longer neck Importance of Lamarck’s Theory • Recognized that life forms were connected • Recognized that there is variation in traits • Recognized that evolution requires time (Earth is Old). • Recognized that inheritance is an important aspect of adaptation Darwin (1809-1882) “On the Origins by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle of Life” • Two Major Ideas: – Common Descent All living and extinct species descended from one or a few common ancestors. • aka: Macroevolution – Adaptation occurs by Natural Selection The characteristics of organisms change through time as a result of natural selection. • aka: Microevolution The only figure in “On the Origins….” Darwin’s Idea of Common Decent Implies: (1) Branching evolution (2) That species accumulate differences over time Genus 1 Species 1 Species 2 Genus 2 Species 1 Extinction Differences Accumulate Over Time Species 2 Species 3 Species 5 Species 4 Systematists Study Differences Among Species to Reconstruct Phylogeny (i.e. Phylogeny = Genealogy of Species) http://phylogeny.arizona.edu/tree/ Evolution by Natural Selection What is adaptation? Process of genetic change whereby individuals of a population become better suited to their environment Evolution of developmental timing: metamorphosis vs paedomorphosis ephemeral pond Metamorphosis Time Adaptation to Permanent Pond Hatching no metamorphosis Paedomorphosis Evolution After Darwin Most folks accepted idea of common descent, but not natural selection. Competing theories were proposed: Orthogenesis: variation in the characteristics of organisms is channeled in pre-determined directions. Macromutation: downplayed the importance of continuous variation and stressed discrete variation. Thought evolution only depended upon mutation rate. The Modern Synthesis (1930’s - 40’s) Synthesis of ideas/concepts among geneticists, natural historians, and evolutionary biologists that modern evolutionary biology is built upon. Emphasized the co-action of random mutation, selection, genetic drift, and gene flow in microevolution. Emphasized that these evolutionary processes were sufficient to account for macroevolutionary trends.