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Evolution Chapter 5 • Natural selection is daily and hourly scrutinizing throughout the world of every variation, even the slightest; rejecting all that which is bad, preserving and adding up all that is good; silently and insensibly working… We see nothing of these slow changes in progress until the hand of time has marked the long lapse of ages. Charles Darwin, On the Origin of Species, 1859 • How exceedingly stupid of me not to have though of that! Thomas Henry Huxley, 1859, after reading On the Origin of Species The Evolution of Evolution • On the Origin of species started a scientific revolution that transformed natural history into modern biology and for ever changed our view of ourselves. • By 1859 was already difficult to interpret life, fossils, and geology as evidence of the book of Genesis. Darwin’s book did not spring out of a vacuum. • The idea that one species might be transformed into another is an old one that continually crops up in western thought. • The Greek philosophers of thee fifth century B.C. promoted the idea that “everything changes”. • The dominance of thee Church in the western civilization put an end to that kind of free thought for over a millennium. • During the 1700s it became increasingly difficult to take Genesis literally. • Difficult to believe that every animal fit Noah’s Ark, and then migrated from Mt. Ararat to their present homes. • By mid-1700’s, the work of taxonomists like Linnaeus had already recognized over 6000 species of animals. • This because exploration in places like Africa, South America, Australia, southeast Asia (marsupials and placental). Fossil Record • The discovery of faunal succession in the early 1800s made impossible to treat all fossils as if they had been victims of a single flood, or even a series of floods. • The complexity of the fossil record showed that life had undergone many changes over time. • Hutton, Lyell and other geologist made it clear that Earth was immensely old and constantly changing not created only 6000 years ago. • By 1840s, geologist had all but abandoned the Bible as having anything to do with the with the fossil record. • A sequence of fossils was establish by creationist geologist more than 40 years before Darwin published his book. • In the 1700s the idea of evolution became more and more popular. • 1749, George-Louis Leclerc, Count of Buffon (1707-1788). Historie naturalle- a 34-volume work on evolution and suggested that Earth was 75,000 years old. • Lamarck, botanist, was assigned the work in the museum of invertebrate zoology which he completely reorganized lying the foundation of modern invertebrates. • Lamarck coined the term “Biology” to combine zoology and botany. His experience allow him to learn and see the diversity of life and published “Philospphie Zoologique” ion 1809. • He saw the interconnections and variability of life and realized that species were not fixed. • He arrange animals in the “scale of creation”. • The “ladder of creation” placed corals, worms, and other invertebrates at the bottom and “lower” vertebrates in the middles, mammals higher, and humans in the top of the ladder. • Various ranks of cherubim, seraphim, angels, and archangels were on the higher rungs, culminating with God. • Lamarck believed in life being spontaneously generated out of mud and moving up the ladder to the top.Those evolving for a long time were mammals or even humans. • Typical of that time Lamarck work was philosophical and speculative with little or no hard evidence or experimental data. • Lamarck also established “inheritance of acquired characters”- a blacksmith will pass its on his large muscles to his children, or a giraffe that stretched its neck would pass its longer neck on to its descendants until giraffes reached their current neck. The Evolution of Darwin • Charles Darwin (1809-1882) • He was born the same year that Lamarck published his evolutionary theory. His grandfather was the king’s physician and had published a poem that promoted evolution. • Darwin’s father was also a physician and planned his son to follow in the same family calling. Darwin • Darwin did not have the stomach for the profession. Instead he developed a passion for natural history and was very influenced by the zoologist Robert Grant, who taught in Edinburgh but was a follower of the French evolutionists. • Darwin dropped out of medical school, and was send to Cambridge to study theology so he would not disgrace the family. • In Cambridge he became more involved with natural history and was trained by the botanist, John Stevens Henslow and the geologist Adam Sedgwick. • He took part of the world oceanographic voyage on the H.M.S. Beagle. He became the ship’s naturalist. • The voyage took five years to go around the world. • Darwin collected animals and fossils. • In Galapagos darwin observed that each island had its own unique species of tortoises, and the finches had been modified to take over many of the roles taken by other birds on the mainland. • While in the ship Darwin read the three volumes of Lyell’s “Principles of Geology”. • By 1842 Darwin had a rough sketch of his evolutionary theory, but he sealed and put away with instruction for her wife to publish it after he died. Alfred Russel Wallace (1823-1913) • Wallace developed his own concept of natural selection. He got his ideas while traveling in Indonesia to collect animals in an expedition. He wrote a letter to Darwin with his finding. • Darwin not wanting to rob Wallace of due credit but also not wanting to lose credit for his own appealed to the geologist Charles Lyell and the botanist Joseph Hooker. • They decided to that both Darwin’s 1842 and Wallace 1858 work be read at the 1858 meeting of the Linnean society so that they will get equal credit. • However, they were considered not important. That years report of the society mentioned that no important discoveries were done. • Darwin summarized his ideas in a 155,000word book: On the Origin of Species by Means of Natural Selection. • It sold out all 1250 copies on the day it was published and went through six editions while Darwin was alive. On the Origin of Species by Means of Natural Selection • Darwin’s argumentation was very simple yet very clever. • First, he drew an analogy to the artificial selection practiced by the breeders of domesticated animals. • If wild dogs could be modify into beasts as different as house dogs, then species were much more flexible than naturalist admitted. • Then he draw arguments from Malthus (humans are reproducing at higher rates than resources) animals are capable of exponential growth of populations, yet in nature most animals populations remain constant so:more young are born than can survive. • Next he described how natural populations are also highly variable, and pointed to the experiments on domesticated animals that showed how these variations were heritable. • His major conclusion: Organism that inherit favorable variations for their immediate environment will tend to survive more often than others. Darwin called this idea Natural selection. In Africa indivuduals with heterozygous (Aa) have a greater resistance to malaria than normal individuals. AA are selected against by Malaria, And (aa) individuals die from sickel-cell anemia. Heterozygotes advantage. Aa - Aa mating results in 1/4 (aa) offsprings combination and die. Heterozygote advantsage. Neutralism-some changes are adaptively neutral. 64 possible combination of genetic code, only 20 aminoacids plus a few stop codes. If 1-U and 2-C is aminoacid-serine no matter who 3 is.