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In 1831, Charles Darwin sailed to the Galapagos islands aboard the HMS Beagle. He was hired to be the ship's naturalist, and he was required to document the plants and animals observed on the HMS Beagle's five year journey. Creationists: Believe God created all things at the same time Evolutionists: Believe all living things come from a common ancestor having changed very slowly over timeDarwin's Theory: Darwin proposed the Theory of Natural Selection. He proposed that over a very long period of time, natural selection can lead to changes. "Survival of the fittest" (competition) is part of this theory. Those organisms best suited to an environment will survive. Helpful variations(mutations) and adaptations(traits that help an organism survive) may gradually accumulate in a species while unfavorable ones may disappear. Evolution After Darwin returned to England he kept thinking about what he had observed during his five year journey aboard the HMS Beagle. In the Galapagos Islands, Darwin had observed adaptations that helped organisms survive and reproduce in different environments. Darwin reasoned that organisms that had arrived on the islands faced conditions that were different from those on the mainland. Over many generations, the species became better adapted to the new conditions. These ideas came to be known as Darwin's Theory of Evolution. Evolution is the gradual change in a species over time. Darwin wrote these ideas in a book entitled The Origin of Species. What is Selective Breeding? The process of selecting a few organisms with desired traits to serve as parents of the next generation Selective breeding was commonly used by farmers during Darwin's time. Natural Selection: What factors affect the process of natural selection? 1. Overproduction This occurs when species produce many more offspring than can possibly survive. Since there is limited food, water, and living space, offspring struggle to survive. Those best able to survive will eventually pass on their genes to their offspring. 2. Competition Limited resources may create competition within a species. Survival of the fittest results. 3. Variation These variations are differences in traits within a species. Sometimes certain traits may be more favorable than others. Those organisms displaying the favored trait will survive and reproduce. What evidence supports the theory of evolution? Since Darwin's time, scientists have found that a great deal of evidence supports the theory of evolution... 1-Fossil records 2-Embryology 3-Homologous structures 4-DNA How do fossils form? Most fossils form in sedimentary rock. This occurs when animals die and become buried in sediments. Eventually the organism's remains are replaced by minerals. Vocabulary: Petrified Fossils-A fossil formed when minerals replace all or part of an organism. The remains are actually changed into rock. Mold-A type of fossil formed when a shell or other hard part of an organism dissolves, leaving an empty space in the shape of the part Cast-A type of fossil that forms when a mold becomes filled in with minerals that then harden. Preserved Remains-Remains of organisms that become preserved in substances such as ice or amber How can you determine a fossils age? 1-Relative Dating May be used to determine which of two fossils is older. It does not reveal a fossil's actual age. 2-Radioactive Dating Allows scientists to determine the actual age of fossils. This technique measures the amount of radioactive elements contained in a fossil. Using the rate of decay for that element(half-life), scientists can calculate a fossil's age. What is half-life? The time it takes for half the atoms of a sample of a radioactive element to decay, or break down. What is mass extinction? When many types of organisms become extinct at the same time. What is gradualism? A theory that evolution occurs slowly but steadily. What is punctuated equilibria? Species evolve quickly over short periods of time. These periods are separated by long periods of little or no change.