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Understanding Natural Selection

Understanding Natural Selection. The Theory of Evolution (See Chapter 16 in your text). What do these words mean?. Evolution Theory. What is a theory ?. Common English language A theory is... A best guess A hypothesis Something you aren’t sure about . Science A theory is...

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Understanding Natural Selection

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  1. Understanding Natural Selection The Theory of Evolution (See Chapter 16 in your text)

  2. What do these words mean? • Evolution • Theory

  3. What is a theory? • Common English language A theory is... • A best guess • A hypothesis • Something you aren’t sure about • Science A theory is... • The result of many experiments that all show the same thing • NOT a guess • No evidence has been found against it

  4. What is evolution? • The processes that have transformed life on earth from it’s earliest forms to the vast diversity seen today. • A change in the genes! • MANY experiments and observations show the same conclusion

  5. Which genes had better evolutionary fitness? Before the industrial revolution After the industrial revolution

  6. What happened to the population over time? • Which moths were the most common after the trees changed? • Why did the population change? • Could individual moths change color? • How would you observe this in the local environment? • Did a new speciesform?

  7. What does a population need so it can evolve? 1. Inherited Variation

  8. What does a population need so it can evolve? 1. Inherited Variation 2. Overproduction

  9. What does a population need so it can evolve? 1. Inherited Variation 2. Overproduction 3. Struggle to Survive

  10. What does a population need so it can evolve? 1. Inherited Variation 2. Overproduction 3. Struggle to Survive 4. Successful Reproduction

  11. Is there enough food for all? • Thomas Malthus (late 1700s) Units of Food Population Size Malthus said: At some point, we will run out of food! Years

  12. How old is the Earth? How long does it take to change? • Charles Lyell – Principles of Geology • The earth is very old • Many small changes over a long time can produce big differences

  13. History of the theory of Natural Selection • How did the giraffe get its long neck? (Early ideas about natural selection)

  14. History of the theory of Natural Selection • Jean-Baptiste de Lamarck (1809) • If an organism uses a body part it will get stronger • Then it can pass on that trait to its offspring

  15. What do you think? Is that true? • Acquired characteristics CAN’T be passed on • You can only pass on what is in your DNA (which doesn’t change)

  16. Charles Darwin • Voyage of the Beagle (1831 – 1836) • Looked at specimens from all over the world • Saw similarities and differences and tried to explain them

  17. Voyage of the HMS Beagle

  18. What did Darwin see? • Famous example of finches in the Galapagos Islands • Each slightly different with different food sources

  19. How did the finches get that way? • Ancestor finch arrives on an island • Finches spread to different islands, each with a different type of food • Birds with beaks that eat the food best survive better and reproduce more • There are more birds with the right kind of beak on that island • Continues for many years...

  20. But Darwin was not the only one! • Another (younger) scientist was studying the same thing • Alfred Russel Wallace came up with the theory of Natural Selection too • Sent a letter to Darwin asking advice • They published the idea together... http://www.pbs.org/wgbh/nova/darwin/program-q-300.html

  21. Why did Darwin wait more than 20 years to publish his ideas? • Darwin started thinking about Natural Selection in 1836 • He published The Origin of Species in 1859 • Why did he wait so long? What do you think?

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