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What is Evolution?

What is Evolution?. Unit 6: Seventh Grade. Theory vs. Fact. Theory. Fact. An idea that has not been proven to be unequivocally true Examples: Big Bang The extinction of the dinosaurs. An idea or truth that has been proven to be unequivocally true Examples:

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What is Evolution?

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  1. What is Evolution? Unit 6: Seventh Grade

  2. Theory vs. Fact Theory Fact • An idea that has not been proven to be unequivocally true • Examples: • Big Bang • The extinction of the dinosaurs • An idea or truth that has been proven to be unequivocally true • Examples: • For every action, there is an equal and opposite reaction • 6+6=12

  3. Using these pictures, describe a frog:

  4. Differences among Organisms • As you can see, each frog has a different characteristic that might help the frog survive. • An adaptation is a characteristic that helps an organism survive and reproduce in its environment. • Look again at the picture --- what adaptations might the frogs have to survive their environment?

  5. Adaptations • May be: • Physical –something an organism has • Long neck to reach food • Long legs to run faster • Behavioral – something an animal does • Nocturnal • Burrows

  6. Species • A species is a group of living things that can mate with one another and produce fertile offspring. • Groups of individuals of the same species living in the same place make up a population.

  7. Do species change over time? • Scientists think that the Earth has changed a great deal during its history, and that living things have adapted to the Earth’s changes and have changed as well. • http://www.youtube.com/watch?v=dcUL_pBiPc0&safety_mode=true&persist_safety_mode=1

  8. For example, the most evil creatures EVER… snakes • Before snakes slithered, they had limbs similar to those of lizards. • To better adapt to their environment of small holes in the ground, they lost their legs. • This allowed them to fit into a tighter space, in which they could hide from predators. • This was true mostly for the first species of snakes, at a time when most reptiles didn't go above the ground for their prey but burrowed around in search of food. • Modern boas and pythons actually still have a small stub where their legs used to be millions of years ago.

  9. Scientists have observed that species have changed over time • They have also observed that inherited characteristics in populations change over time. • Scientists also think that as populations change over time, new species form. • New species descend, or come from, older species. • This process of populations changing over time is called evolution.

  10. The Evidence of Evolution • Evidence that organisms have changed over time is buried within the Earth’s crust. • They layers are made of different kinds of rock and soil stacked up on top of each other.

  11. Layer Upon Layer, Upon Layer …. • These layers, form when sediments such as dust, sand or soil are deposited in an orderly fashion by wind, water and gravity. • The Law of Superposition states that older layers are deposited before newer layers and are buried deeper within the Earth.

  12. And under all those layers is evidence! • And the evidence is the remains or imprints of once living organisms. • These remains or imprints are called fossils. • Fossils can be complete organisms, parts of organisms, or just a set of footprints.

  13. The Fossil Record • By studying these fossils, scientists have made a timeline called the fossil record. • The fossil record organizes fossils by their estimated ages and physical similarities.

  14. Evidence of Ancestry • The fossil record is important in that it provides evidence about the order in which species have existed. • The fossils found in newer layers of the Earth have more similarities to present day organisms. • Fossils found in lower layers are less similar to present day organisms or may not exist anymore.

  15. Common Ancestry • From this evidence, scientists have observed that all living things have characteristics in common and inherit characteristics in similar ways. • Scientists theorize that all living species have descended from common ancestors. • Evidence of common ancestry can be found in fossils and in living organisms • Evidence that groups of organisms have common ancestry can also be found by comparing their DNA

  16. In conclusion • When scientists compare common traits, fossil evidence and the DNA of organisms it supports the theory of common ancestry

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