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  • 2 Definition Evolution is the slow, gradual change in a population of organisms over time. copyright cmassengale
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  • Charles Darwin is credited with being the father of modern evolutionary theory, though he was not the first person to formulate ideas about how life on earth has changed over time. He was an unusual person to have on board ship in the 1830s. He could read and write well, and was skilled in the use of scientific principles used to gather data on the wide variety of plants and animals they would see during their several year survey of South America and areas of the South Pacific. On these voyages first began to think about how plants and animals had come to have the characteristics they had. For 20 years, Darwin studied nature, and the more he observed, the more convinced he became that the Biblical account of Genesis, which holds that all living things on Earth were created in their original state in the first days of creation, could not be true. Finally, in 1859, Darwin published his beliefs about life on Earth in The Origin of the Species. In this work, Darwin explains a theory about the development of life on Earth that comes to dominate natural science for the next 150 years. Darwins argument also became and remains one of the most controversial theories in history.
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  • 4 HMS Beagles Voyage copyright cmassengale
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  • Darwin- Charles Darwin first put forth the idea that living organisms on earth have changed or adapted over periods of millions of years. These changes are believed to have resulted from a process of random genetic mutations that ended up somehow benefiting an organism giving it an advantage over other members of the same species. (In MOST cases, mutations are harmful or even fatal to the organism.) This often resulted in the development of different forms of the same gene. Unique physical characteristics or abilities that allow an organism to survive in its environment are known as adaptations. Eventually, enough changes occurred that entirely new species of organisms developed. This process has been called speciation. Evolutionary scientists cite evidence of evolution in the fossil record, our growing knowledge of genetics, and in comparative observations of modern plants and animals.
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  • Evolutionary theory is broken down into several major ideas: 1.Organisms have physical characteristics, adaptations, that allow them to survive in their environments. 2.Variations occur within species. We have seen that in our study of genetics. We learned there are different forms of genes resulting from slight mutations over time. 3.If one form of a gene or adaptation gives the organism a survival advantage over other members of the same species, that form of the trait will ultimately win out and be passed on to the offspring. This competition between organisms is known as natural selection: survival of the fittest. 4. Over time environmental conditions have changed. Organisms that were unable to adapt to the changes became extinct. 5. Over a period of millions of years, enough changes occur within certain species of organism that an entirely new species results. This is called speciation.
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  • 8 What variations can you observe in these animals?
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  • The Goldenrod Crab Spider has two common color variations. How might this be explained by natural selection? The ancient Goldenrod spiders with white or yellow coloring had a survival advantage over those that were a different color in this particular environment. The yellow and white colored spiders survived better and produced more offspring with the yellow and white color trait.
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  • Adaptations can be related to size, color, shape, or functionality of a particular body part. What are some of the adaptations for the organism shown here? This insects adaptation is shape and color. It is a leaf mimic.
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  • What are some of the adaptations for the organism shown here?
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  • 15 Common Descent 6. Darwin proposed that organisms descended from common ancestors that gradually changed over time into entirely new organisms.
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  • Believed evolutionary process of of horses, elephants, and whales.
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  • It was Darwins belief that natural selection could not be observed by humans because it took place over such tremendous lengths of time-millions of years in some cases. However, modern examples of variation within populations of organisms of the same genus are used to demonstrate natural selection at work.
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  • In our study of genetics we learned about selective breeding and genetic modification. Both involve humans manipulating breeding to produce desired outcomes. Selective breeding has resulted in the over 400 breeds of dogs we have on earth today. Most domesticated animals and food crops in our world today are a result of selective breeding. When nature selects which forms of traits will be passed on, it is referred to as natural selection. When humans manipulate this process and select which desired traits will be passed on, it is known as artificial selection. Artificial selection has resulted in new breeds of organisms, but not in entirely new species of organisms.
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  • These two animals are different breeds but the same species. What human- engineered process has resulted in the wide differences in these animals? How does this process differ from natural selection?
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  • Commonly Identified Examples of Natural Selection Darwins finches- During his exploration of the Galapagos Islands, Darwin observed that the beaks of the finches differed on many of the islands. Upon closer observation, Darwin concluded that the beak shapes had changed as a result of their surroundings, most importantly the source of food on each island for the finches. The beak shape on each island was the best shape for accessing the type of food finches ate on that island, but would not have been the best shape on one of the other islands. Darwin argued that as the sea level of the earth rose millions of years ago, populations of the original finches were trapped on small islands and became isolated from the other finches by stretches of ocean. Over millions of years, the form of the gene that best served the finches on each of the islands (based on the main food source for finches on each island) won out and that form of beak shape became the most common on that particular island.
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  • 24 The same thing appears to hold true in the tortoises living on the different islands of the Galapagos as well.
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  • Peppered Moth- In Europe prior to the Industrial Revolution (1800s), Peppered moths generally had a light, ashy color and blended well with the light colored bark of local oak trees. However, as more coal was burned in homes and factories throughout Europe, the trees became darkened with coal soot. The light colored moths stood out more and became easy prey for predatory birds. However, some of the moths had a different form of the gene for coloring and were darker. This form of the gene became favored in that forest. The darker form of the gene won out against the lighter form. Darwin called such a process Natural Selection. In other words, nature chose which genetic trait would be favored in a competition between different forms of the same gene.
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  • How Isolation Can Lead to Biological Change When a population of organisms becomes isolated from others of the same population, one form of a characteristic can become favored over others in this new or changed environment. The favored trait is the trait that gives the organism a survival advantage over organisms that do not have this form of a trait. Over time, the favored trait may become the trait that becomes the most prominent in the phenotype of the species. The other forms of the gene may disappear completely from that population of organisms.
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  • Populations can become isolated by changes in geography, such as the development of impassable mountain ranges or changes in the water levels in a body of water. Isolation also resulted when continents separated. The Galapagos Islands, Australia, Tasmania, and Madagascar are famous for having species of plants and animals that are unlike any found elsewhere in the world. Remote islands like these and smaller islands are showcases for the effects of isolation on a population of organisms.
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  • Lake Tanganyika Cichlids- This African lake is known for its many varieties of cichlids, a tropical fish very common in pet stores around the world. It is believed that all cichlids evolved from one species of cichlid that existed millions of years ago. Geological evidence suggests that during several points in the history of the lake, the water level decreased and a number of smaller lakes existed that were separated by shallow islands that had once been under water. Cichlids that were trapped in these smaller lakes are believed to have evolved and adapted based on the unique conditions of each lake. Forms of genes were favored in some lakes but not others. E

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