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The History of Evolution

The History of Evolution. Historical Thoughts on Evolution. Aristotle (384-322 BC): derived a concept called Scala Naturae – “Great Chain of Being” or “The Ladder of Life” Hierarchical chain starting with God & progressing downward to less complex organisms

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The History of Evolution

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  1. The History of Evolution

  2. Historical Thoughts on Evolution • Aristotle (384-322 BC): derived a concept called ScalaNaturae – “Great Chain of Being” or “The Ladder of Life” • Hierarchical chain starting with God & progressing downward to less complex organisms • Connects all living things moving toward a goal (to be perfect) • Literal Biblical view: the world was created in 6 days • Earth is 6,000 years old. • All species were created as they are today.

  3. Influences from Geology • James Hutton: gradualism • Things that change the Earth take a LONG time. • Charles Lyell: current Earth-shaping processes are the same as the past • Stressed that scientists must explain past events in terms of processes that they can actually observe • Wrote Principles of Geology, which was read by Darwin

  4. Influences from PaleontologyThe study of collecting & studying fossils • William Smith: each layer of rock had unique fossil records • The older the layer, the more dissimilar the organisms were to present forms. • George Cuvier: documented extinction as a common occurrence

  5. Influences from Economics/Sociology • Thomas Malthus (1798): population size linked to poverty & disease • If the human population continued to grow unchecked (grows exponentially), it will be limited by space & food supply.

  6. Thomas Malthus (1798) • Thought that when populations outgrow their resources, competition kicks in Do you believe it? Why or why not? Does this apply to just humans?

  7. Sea turtles lay hundreds of eggs, but only a few survive. WHY?

  8. Trees produce hundreds of seeds, how many actually mature? WHY?

  9. There must be some selecting factor that decides which organisms are most fit for survival…

  10. Jean-Baptiste Lamarck (1809)Inheritance of Acquired Traits • Believed that organisms would gain or lose features if they overused or did not use the traits • These traits could be passed on to their offspring. • One of the 1st to propose a mechanism to explain why organisms change over time!

  11. Lamarck’s Hypothesis (1809) • Tendency Toward Perfection • Organisms are continually changing & acquiring features that help them live more successfully in their environments. • Use & Disuse • Organisms could alter the size or shape of particular organs by using their bodies in new ways. • Inheritance of Acquired Traits • If during its lifetime an organism somehow altered a body structure, it would pass that change on to its offspring.

  12. The evolution of Fiddler Crabs according to Lamarck:

  13. Lamarck’s Hypothesis Is this idea supported by scientific evidence? WRONG!!

  14. Why is Lamarck’s hypothesis wrong? That’s like me saying that I’d like to become a basketball star… so I stretch my legs until they’re really long & I’m 7 feet tall!

  15. How did his hypothesis positively influence evolutionary thought? • His hypothesis on evolution was incorrect in several ways. • BUT he was the 1st to recognize that organisms are well suited to their environment! • Key concept for future work!

  16. Organisms are well suited for the environment that they live in. • Polar Bears have: • A white coat for camouflage • Thick layers of fur & fat for warmth • Water repellent fur • Large feet to evenly distribute weight on ice • Camels have: • Large feet to balance on sand • Ability to store more water by infrequent urination & sweating • 2 rows of eyelashes to keep sand out of eyes

  17. Charles Darwin (1831) • Sailed on the H.M.S. Beagle around the world • Collected plants, animals, fossils, OBSERVED

  18. Some of Darwin’s Observations… Species on the Galapagos Islands were similar to the mainland, but differ in each environment. There are several types of finch in the Galapagos Islands. They’re similar to the finches found in Ecuador, but each is a little different.

  19. Some of Darwin’s Observations… Variation exists within a population & some of that variation is inheritable. Some peppered moths carry the genes for white coloration, but some carry the genes for black coloration. Which moths do you think will survive to pass on their genes?

  20. Some of Darwin’s Observations… Similar habitats around the world don’t have the same animals & plants, but they have similar characteristics for that environment. Capybara Beavers are found in North America, while Capybaras are found in South America. HOWEVER, both species live in watery environments & have similar characteristics (like webbed feet). Beaver

  21. Charles Darwin • Influenced by the work of Malthus • Darwin thought that since plants & animals have more offspring than humans, the “Struggle for Existence” would apply more strongly to plants & animals. If all finches ate the same type of food, there would be too much competition.

  22. Charles Darwin • Also influenced by Lyell’s work • Darwin realized that if the Earth could change over time, life itself might change over time in response to physical changes of the Earth & that the changes he proposed would require many, many years.

  23. The Scientific Theory of Biological Evolution • 1859: Charles Darwin published On the Origin of Species by Means of Natural Selection • He believed that populations evolved by Natural Selection. • Evidence for this hypothesis has since been described in many diverse studies & is well supported! • Darwin’s original hypothesis is now known as the Scientific Theory of Biological Evolution.

  24. Lamarck vs. Darwin If Lamarck was wrong, how is Darwin’s theory any different?

  25. How did elephants get their long trunks? Try to put both sets of cards in order, then try to decide whose theory is whose! Which one is Darwin? Which one is Lamarck?

  26. Darwin or Lamarck? Lamarck!

  27. Darwin or Lamarck? Darwin!

  28. Studies that support Darwin’s theory: • Fossil Record • Population Genetics • Animal Behavior • DNA Fingerprinting • Antibiotic Resistance in Bacteria

  29. Before you leave… • On a sheet of paper (share!), write your response to the following: Thomas Malthus believed that the human population would naturally be kept in check by lack of food, disease, etc. Do you believe that this is happening to the human population today? Why or why not?

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