beginnings of modern evolutionary thought charles darwin hypothesized that species were modified by...
TRANSCRIPT
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