Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Beginnings of Modern Evolutionary Thought • Charles Darwin hypothesized that species were modified by natural selection. • Natural Selection- organisms best suited for their environment reproduce more successfully • Over many generations, the proportion of organisms with favorable traits increases in a population. How did Darwin Come up with his hypothesis? • Spent 5 years on a ship called the Beagle and sailed around the world and made various stops • When the ship stopped in a new place, he would collect specimens and keep careful records of his observations Darwin’s Theories • Descent with modification- newer forms of life are actually modified descendents of older species • All species had descended from one or a few original types of life • Based this on what he saw with the finches from the Galapagos Islands What other scientists influenced Darwin? • Thomas Malthus- studied populations -found that populations can double or grow exponentially • - Darwin noticed that most populations did not grow exponentially because environmental factors limit growth Because of Malthus….Darwin came up with the following: • Fitness- how well an organism does in an environment defined by reproductive success • An individual with high fitness is well adapted to its environment and reproduces more successfully (survival of the fittest) -A population of organisms adapt to their environment as their proportion of genes for favorable traits increases -Organisms don’t select traits, environments do! -If the environment changes so fast that the organisms can’t adapt quickly enough, mass extinctions occur. Alfred Wallace • He unknowingly came up with the same theory of evolution as Darwin • He asked Darwin to read his findings and once Darwin saw how similar his thoughts were to his own he know he couldn’t put off publishing his findings anymore. Lamarck • He believed that acquired traits were passed on to offspring • Acquired traits aren’t determined by genes, they are something that arises during the organism’s lifetime as a result of behavior or experience • Lamarck thought that a lizard that didn’t use its tail would have offspring that would have a smaller tail. • He was the first to say that organisms change over time, descending from older, similar organisms Lamarck’s “Use/Disuse Theory” Charles Lyell • Wrote a book called “Principles of Geology” which was centered around the gradual change of the earth -ex: in Lyell’s book, he talked about how a valley could have been formed by the gradual weathering of the earth by a river • Darwin applied this knowledge of the earth to organisms