Evolution Notes


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Evolution Notes

  1. 1. The Evolution of Living Things Changes over Time
  2. 2. Differences Among Organisms Adaptation: a characteristic that helps an organism survive and reproduce in its environment Adaptations can be physical, such as a long neck on a giraffe or striped fur Adaptations may be behaviors that help an organism find food (like hunting at night), protect itself (skunk spraying noxious smell), or reproduce
  3. 3. Examples of Adaptations The red-eyed tree frog hides among a tree’s leaves during the day and comes out at night
  4. 4. The bright coloring of the strawberry poison arrow frog warns predators that the frog is poisonous
  5. 5. The smoky jungle frog blends into the forest floor. This adaptation helps the frog protect itself from predators.
  6. 6.  It is believed that a giraffe’s neck elongated over time to adapt to a food shortage. With a long neck, a giraffe can reach the highest branches for leaves. This gives it an advantage over other animals.
  7. 7. Species: group of organisms that can mate with one another to produce fertile offspring  Groups of individuals of the same species living in the same place make up a population
  8. 8. Do Species Change Over Time?  The species that live on Earth today range from single-celled bacteria to multicellular fungi, plants, and animals  Scientists think that Earth has changed a great deal during its history, and that living things have changed, too  Earth is estimated to be 4.6 billion years old  Many species have existed over time, and many have died out
  9. 9. Scientists have observed that: *species have changed over time *inherited characteristics in populations have changed over time *new species have formed—therefore, newer species descend from older species Evolution: the process in which populations gradually change over time
  10. 10.  Earth’s crust is arranged in layers made up of different kinds of rock and soil stacked on top of one another  Layers form when sediments, particles of sand, dust, or soil are carried by wind and water and deposited in an orderly fashion— sedimentary rock  Sometimes, the remains or imprints of once-living organisms are found in the rock—these remains are called fossils Evidence of Changes Over Time
  11. 11.  Fossils can be a whole organism, part of an organism, or just a set of footprints
  12. 12.  Fossil record: a historical sequence indicated by fossils found in layers of the Earth’s crust -organizes fossils by (1) their estimated ages and (2)physical similarities -fossils found in newer layers of Earth’s crust tend to be similar to present-day organisms
  13. 13. Evidence of Ancestry  The fossil record provides evidence about the order in which species have existed  Scientists observe that all living organisms have characteristics in common and inherit characteristics in similar ways  Scientists believe that all living species descended from common ancestors -evidence of this is found in fossils and in living organisms
  14. 14.  Scientists examine the fossil record to figure out the relationship between extinct and living organisms  Models may be drawn to show how several species were once related
  15. 15. Example:  Scientists think that whales and some types of hoofed mammals, such as camels and hippos, have a common ancestor
  16. 16. Examining Organisms  This ancestor was probably a mammal that lived on land between 50-70 million years ago  Examining an organism carefully can give scientists clues about its ancestors  Example: Whales seem very similar to fish, but whales have live young and breathe air, which makes them a mammal. These traits show scientists that whales evolved from ancient mammals.
  17. 17. Scientists use information about living and ancient species to sketch out a “tree of life” that includes all known species
  18. 18. Comparing Organisms  Evidence that groups of organisms have common ancestry can be found by comparing the groups’ DNA  Organisms contain evidence that populations and species undergo changes in traits and DNA over time
  19. 19. Example: What does your arm have in common with the front leg of a cat, a front flipper of a dolphin, or the wing of a bat?
  20. 20.  These structures do not look alike and are not used in the same way  Under the surface there are similarities  These similarities suggest that cats, dolphins, bats, and humans had a common ancestor
  21. 21.  Over million of years, changes occurred in the limb bones of the ancestor’s descendents  Eventually, the bones performed different functions in each type of animal
  22. 22. Comparing DNA  Traits are inherited through DNA’s genetic code  Example: the DNA of a house cat is similar to the DNA of a tiger
  23. 23.  Scientists find that species that have many traits in common do have similarities in their DNA  The fact that all existing species have DNA supports the theory that all species share a common ancestor