Evolution PowerPoint

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CHAPTER 15:

CHAPTER 15 Theory of Evolution

Definition:

Definition Evolution is the gradual change in a population of organisms over time. Population - all individuals of a species that live together in one place at one time

Ideas of Darwin’s Time - Europe 18th century:

Ideas of Darwin’s Time - Europe 18 th century All species were permanent and unchanging Earth was only thousands-not billions-of years old This started to change as scientists began to present other evidence…

Ideas of Darwin’s Time - Europe 18th century:

Ideas of Darwin’s Time - Europe 18 th century Ideas about Geology Rock Layers called “strata” form over time Lower strata were formed first and are thus the oldest Different strata contained fossils from different kinds of organisms

Ideas of Darwin’s Time - Europe 18th century:

Ideas of Darwin’s Time - Europe 18 th century Charles Lyell Thought that it would take the Earth millions of years to look like it does today Darwin read about Lyell’s work while on his voyage and was excited that these ideas fit with the evidence he was gathering.

Ideas of Darwin’s Time - Europe 18th century:

Ideas of Darwin’s Time - Europe 18 th century Lamarck’s Theory of Evolution Jean- Baptiste Lamarck was one of the first scientists to understand that change occurs over time . Use & Disuse - Organisms could change size or shape of organs by using or not using them

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Ideas of Darwin’s Time - Europe 18 th century Example : Giraffes’ Necks Longer (from stretching)

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Ideas of Darwin’s Time - Europe 18 th century Traits acquired during one’s lifetime would be passed down to offspring Example : Clipped ears of dogs could be passed to offspring!

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Lamarck’s Theory of Evolution Visual Concept

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Ideas of Darwin’s Time - Europe 18 th century Lamarck’s Mistakes Lamarck did NOT know how traits were inherited (through genes) Genes are NOT changed by activities in life Change through Mutation occurs before an organism is born Lamarck’s ideas were disproved; however, he was the first to realize that populations of organisms change over time. He set the stage for the “father of evolution”: Charles Darwin

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Joined crew of HMS Beagle, 1831 The Beagle was chartered for a five-year mapping and collecting expedition to South America and the South Pacific. Charles Darwin (1809-1882)

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Darwin’s job as the ship’s naturalist was to collect specimens, make observations, and keep careful records of anything he observed that he thought significant. When Darwin returned to England in October 1836 , his collections from the voyage were praised by the scientific community. Darwin sent his bird collections from the Galápagos Islands (small group of islands 1000 km west of South America) to an ornithologist. He reported that Darwin had collected 13 similar but separate species of finches . Each finch species had a distinctive beak specialized for a particular food source . Charles Darwin

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Darwin Finches Visual Concept

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The similarities of the finches led Darwin to infer that the finches shared a common ancestor . The ancestors could have flown to the Galápagos Islands from elsewhere sometime after the islands were formed. Charles Darwin

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Darwin’s Dangerous Idea Video Clip http://www.youtube.com/watch?v=_9p5fQVvR_E

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Darwin proposed the theory of natural selection as the mechanism for evolution . In forming his theory, Darwin thought carefully about the forces that could cause changes in organisms over time . Evolution by Natural Selection

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The following diagram represents the process of natural selection . Evolution by Natural Selection

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A trait that makes an individual successful in its environment is called an adaptation . Those individuals that pass on more genes are considered to have greater fitness . Evolution by Natural Selection

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There is variation in traits For example, some beetles are green and some are brown . Example of how natural selection works--imagine a population of beetles:

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There is differential reproduction In this example, green beetles tend to get eaten by birds and survive to reproduce less often than brown beetles do. Example of how natural selection works--imagine a population of beetles:

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There is heredity The surviving brown beetles have brown baby beetles because this trait has a genetic basis. Example of how natural selection works--imagine a population of beetles:

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End result The more advantageous trait, brown coloration, which allows the beetle to have more offspring, becomes more common in the population and therefore is an adaptation . If this process continues, eventually, all individuals in the population will be brown. Example of how natural selection works--imagine a population of beetles: "Survival and Reproduction of the Fittest"

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Environments do not create adaptations. Adaptations arise from random mutations in one of the sex cells of a parent . If a particular mutation helps an organism survive better than others, it will reproduce more and pass on the mutation to its offspring. Eventually, all the organisms without the mutation will die out and all members of the species will have the mutation. When this happens, the population of organisms have adapted to the environment. This change in genes as organisms adapt is called evolution . Where do adaptations come from?

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The environment determines what will be an adaptation. Adaptation - a feature in a population that provides some improved function in an environment. Adaptations can take many forms: a behavior that allows better evasion of predators, a protein that functions better at body temperature, or an anatomical feature that allows the organism to access a valuable new resource—all of these might be adaptations. Many of the things that impress us most in nature are thought to be adaptations. Adaptations

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Example : Mimicry of leaves by insects is an adaptation for evading predators. (katydid from Costa Rica) Adaptations

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Darwin’s Dangerous Idea Video Clip http://www.youtube.com/watch?v=MGM3sPCZl94

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