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The Theory of Evolution 1 I. The theory of Evolution by Natural Selection A. Darwin Proposed a Mechanism for evolution 1. The theory of evolution has developed through decades of scientific observations and experimentation. 2 C. Darwin developed his idea (don’t have to write all this, just listen) 1. Darwin had a hard time in school. 2. His father was a wealthy doctor and wanted him to become a doctor or a 3 3. Darwin ditched classes and spent most of his time outdoors. 4. At 16 Darwin was sent away to study medicine. 5. Darwin skipped lectures to collect specimens. 4 7. Darwin did get a degree in theology but he liked science better. 8. Darwin was bored so at 22 he set on the HMS Beagle a boat that would change his life forever. 5 D. Science before Darwin’s voyage 1. Before Darwin most scientists and non-scientists thought that each species was a divine creature, unchanging and existing as it originally created. 2. In 1809 the scientist Jean Baptist Lamarck proposed how evolution occurs. 6 3. He thought that things evolved with the use/disuse theory. 4. According to Lamark that these traits were then passed on to the offspring. 5. We now know this is WRONG 7 E. What Darwin saw during his voyage 1. He saw different animals with different characteristics on the Galapagos Islands. 8 9 10 11 F. Darwin sought a Reasonable Explanation for Evolution 1. When Darwin returned his voyage at age 27, he continued his lifelong study of plants, animals and geology. 12 2. Thomas Malthus helped Darwin out when he wrote the human populations are able to increase faster than the food supply. 13 3. Examples: Tree seeds- Lots but not all of them will develop into a tree. 4. A population consists of all the individuals of a species that live together in one place at one time. 14 5. Darwin realized that Malthus’s idea about the human population apply to all species. 6. Individuals that have physical or behavioral traits that better suit their environment are more likely to survive and reproduce than those that do not have such 15 traits. 7. Darwin called this process natural selection. 8. Darwin suggested that organisms differ from place to place because their habitats present different challenges. 9. The changing of species that results in its better-suited environment is called 16 adaptation. 10. Darwin also noticed that organisms more closely resemble those living in nearby. 11. Darwin published his ideas in 1859. His book was called, “On the Origin of Species by Means of Natural Selection.” 17 http://carrot.mcb.uconn.edu/~olgazh/photogal/galapagos/santa_cruz/ 18 G. Darwin’s Ideas have been updated 1. Natural selection causes change WITHIN populations. 2. We now know that genes are responsible for inherited traits. 19 3. Natural selection causes the frequency of certain alleles in a population. 4. The environment differs from place to place. 5. Isolation is the condition in which two populations of the same species cannot breed with one another. 20 6. As the two isolate populations of the same species become more different over time, they may eventually be unable to breed with one another. 21 7. Over long periods of time, events such as climate changes and natural disasters result in some species becoming extinct. 8. Which means they disappear permanently. 22 II. Evidence of Evolution A. Fossils Provide an objective record of evolution 1. Most scientists agree on the following three things: 23 a. Earth is about 4.5 billion years old. b. Organisms have inhabitant Earth for most of its history. c. All organisms living today evolved from earlier, simpler life 24 2. Paleontologists study fossils to compare the past verse the present. 25 B. Biological Molecules contain a record of evolution 1. If species have changed over time, then the genes that determine their characteristics should also have changed. 2. As species evolved, one change after another should have become part of their genetic instructions through mutations. 26 3. Therefore a species proteins and nucleic acids would show these changes. 27 C. Anatomy and Development suggest common ancestry 1. Comparisons of the anatomy (structures) of different types of organisms often reveal basic similarities in body structures, even though their functions may be very different. 28 2. Sometimes bones are present in an organism but are reduced in size and either have no use or have a less important function . These structures are called vestigial structures. 29 30 3. Homologous structures are structures that share common ancestry. Same structure different function. 4. Example: A whale flipper and a human have the same structure but different function. 31 32 5. Analogous structures are structures that DO NOT share common ancestry. They have the same function but different structure. 6. Example: A bird wing and a butterfly wing both fly but they have different bones. 33 34 7. The evolutionary history of organisms is also seen in the development of embryos 35 D. Does evolution occur in spurts? 1. There are two theories of how evolution occurs. 2. Gradual change over a long period of time leads to species formation called gradualism. 36 37 3. Rapid change in species is separated by periods of little or no change is called punctuated equilibrium. 38 III. Examples of evolution A. Natural Selection changes the makeup of population 1. Cause and effect. Everything that has a cause in nature will have an affect. 2. Example- kettlewell and his moths. 39 40 B. Overview of natural selection 1. All species have genetic variation 2. The environment presents many different challenges to an individual’s ability to reproduce. 41 3. Organisms tend to produce more offspring than their environment can support, thus the animal must survive to live. 4. Individuals that are able to cope with the challenges of their offspring tend to leave more offspring than those 42 less suited. 5. The traits of the individuals best suited to a particular environment tend to increase in a population over time. 43 C. Industrial melanism 44 D. Beaks of finches 1. Beaks of finches evolved to what the finch is eating. 45 46 E. The formation of New Species Begins with Small Changes 1. Species formation occurs in a series of stages. 2. The accumulation of differences between gropes is called divergent. 47 3. Within populations, divergence leads to the formation of new species. This is called speciation. 4. Over time, populations of the same species that differ genetically because of adaptations to different living conditions become what biologists call ecological races. 48 F. Maintaining new species 1. What keeps new species separate? Why are even closely related species usually unable to interbreed? 49 2. See page 293 on frog mating months. 3. Reproductive isolation is the inability of formerly interbreeding groups to mate or produce fertile offspring. 4. Species formation is continuously being documented. 50 THE END 51