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by Natural Selection

Evolution…. by Natural Selection. 1. What is Evolution?. Evolution changes in living organisms over time explains how modern organisms have descended from ancient organisms. Why do we accept this as a Scientific Principle? . Evolution!. 2. What do we know?.

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by Natural Selection

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  1. Evolution… by Natural Selection

  2. 1. What is Evolution? • Evolution • changes in living organisms over time • explains how modern organisms have descended from ancient organisms Why do we accept this as aScientific Principle? Evolution!

  3. 2. What do we know? • A. There are many different creatures on Earth • How do we know this? OBSERVATION Biodiversity of Life on Earth Diversity of Life on Earth What accounts for all this biological diversity? How did all these creatures come about?

  4. DNA cells What do we know? • B. All creatures have common characteristics • How do we know this? OBSERVATION Unity of Life on Earth How could all of life have the same basic features?

  5. What do we know? Life is very old! • C. The Earth is very old • How do we know this? TESTING & OBSERVATION Radioactive Dating of the Rocks What’s happened to life during those billions of years?

  6. What do we know? • D. Creatures have changed over time • How do we know this? OBSERVATION Fossil Record

  7. 3. What has the fossil record shown us? • A. Many creatures that lived in the past don’t exist today OBSERVATION Origin of new species

  8. What has the fossil record shown us? • B. The creatures alive today haven’t always been around OBSERVATION Different species lived in the past

  9. What has the fossil record shown us? • C. Many creatures in the past looked like living ones we see today OBSERVATION “Family Tree” Relatives with similar, but not the same traits

  10. 4. Quick review, so far…. • Many different species alive today • All life shares common characteristics • The Earth is very old • Life is very old • Life has changed over time • The changes have been little changes over long periods of time Evolution But how does this work?

  11. 5. What do we know? • A.Populations are a mix of different individuals • How do we know this? OBSERVATION Variation

  12. What do we know? • B. Organisms have more offspring than the environment can support • C. Not everybody survives • E. How do we know this? OBSERVATION Over-production Competition

  13. Adaptation Variation 6. How does that work? Natural Selection Nature selects the ones that “fit” the environment better … survive & reproduce Over-Production & Competition

  14. 7. What determines survival? • traits that help individuals survive • survive predators • survive disease • compete for food • compete for territory • traits that help individuals reproduce • attracting a mate • compete for nesting sites • successfully raise young Adaptations Survival & Reproduction of the Fittest

  15. Survival & Reproduction of the fittest not the strongest… not the bravest… not the fastest… not the biggest… …the fittest! Adaptations the traits that help an organism fit the environment better to survive & reproduce

  16. 8. Darwin’s Theory of Natural Selection • #1 Overproduction • Organisms tend to have many more than two offspring so at least some will survive (yet populations usually do not grow rapidly in the wild)

  17. #2 Competition - Therefore they must compete for resources (food, space, mates)

  18. Natural Selection • #3 Variation - There is variation within the population. • #4 Adaptation - Therefore some of them must be better adapted to their environment

  19. #5. Natural Selection-the ability of organisms that are best adaptedto survive and reproduce. Those that are less well adapted will not survive.

  20. DNA 9. Evolution explains Unity & Diversity • Evolution explains both • unity of life • similarities between all living things • diversity of life • wide variety of different creatures on Earth

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