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Charles Darwin's Theory of Evolution

Explore Darwin's journey on the H.M.S. Beagle, his observations, and the ideas that shaped his revolutionary theory of evolution.

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Charles Darwin's Theory of Evolution

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  1. Biology Chapter 15: Darwin’s Theory of Evolution

  2. Chapter 15: The Theory of Evolution 15.1 The Puzzle of Life’s Diversity • Evolution – change in a population of organisms over time • Charles Darwin • English Scientist • Considered to be the father • of evolutionary theory • Born Feb 12 1809

  3. Voyage of the H.M.S. Beagle • 1831 Darwin traveled on the Beagle • A 5-year expedition to South America and • South Pacific for mapping and collecting specimens • His job was to collect, study and store biological specimens • His observations in the Galapagos Islands were among his most important • Compared the anatomy of many species of reptiles, insects, birds, plants

  4. Darwin’s observations • He noticed organisms were unique yet similar to species seen in other parts of the world • Grasslands in some regions were similar to one another but were inhabited by very different animals. • The Galapagos Islands were close together but had very different climates. • The shape of the giant tortoises shell and neck length can identify which island a tortoise inhabited • The shape of the finches beak varied from island to island

  5. Fig. 17.5b, p. 275

  6. By the end of his trip he was convinced that evolution occurs, that species can and do change • He knew that many species produce large numbers of offspring and since Earth was not covered with many species he suspected that there must be a struggle for existence among individuals • Only the strongest survive and the weak die

  7. 15.2 Ideas that Shaped Darwin’s Thinking • Hutton • Earth is shaped by geological forces over long periods of time • Estimates earth to be millions, not thousands of years old • Lyell • Processes occurring now have shaped Earth’s geological features over long periods of time

  8. Lamarck • Inheritance of Acquired Traits • Also called use and disuse theory • Selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime • Those traits could be passed on to offspring • Ex. Long necks of giraffes • Big muscles • Evaluating Lamarck’s Hypotheses • Lamarck’s hypotheses of evolution are incorrect in several ways. • Lamarck did not know how traits are inherited • However, he paved the way for the work of later biologists.

  9. Malthus • If the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone. • This information was central to Darwin’s explanations of evolutionary change.

  10. 15.3 Darwin Presents his Case • Publication of Origin of Species • Darwin wrote all of his ideas down, but did not publish them. • He struggled with his ideas because they went against scientific thought at the time • Wallace was a naturalist that had the same ideas as Darwin and was going to publish them. • This forced Darwin to publish his ideas • On the Origin of Species publish in 1859

  11. Inherited Variation and Artificial Selection • One of Darwin’s most important ideas was that organisms of the same species vary from one another • Darwin thought that variation mattered • Artificial Selection – a breeder selects particular traits. This had been done by farmers for years • Darwin wondered if nature selected particular traits

  12. The struggle for existence • Individuals with characteristics that are not well suited to their environment either die or leave few offspring. • Individuals that are better suited to their environment survive and reproduce most successfully. • Natural Selection – organisms with favorable variations survive, reproduce and pass those variations on to the next generation • Darwin also called this “Survival of the Fittest”

  13. Evidence for Evolution • Fossil Record • Darwin saw fossils as a record of the history of life on Earth

  14. Homologous Body Structures • Structural features with a common evolutionary origin • Similar in structure and/or function • Example: whale forelimb, crocodile forelimb, bird wing, human arm

  15. STEM REPTILE PTEROSAUR CHICKEN BAT DOLPHIN PENGUIN HUMAN

  16. Analogous Structure • Do not have a common evolutionary origin • Any body structure that is similar in function but different in structure • Example: butterfly wing and bird wing • Can’t be used to indicate evolutionary relationships, but they do provide evidence of evolution

  17. Vestigial Structure • Any body structure that is reduced in function in a living organism but may have been used in an ancestor • Example: appendix, wisdom teeth, tail bone

  18. Similarities in Embryology • The early stages, or embryos, of many animals with backbones are very similar • Similarities among vertebrate embryos suggest evolution from a common ancestor • These common cells and tissues, growing in similar ways, produce homologous structures

  19. BIRD (chicken) MAMMAL (human) FISH REPTILE adult shark Early human embryo (three millimeters in length) Fig. 20.7, p. 317

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