1 / 24

Bell Work

Bell Work. Half of a Half of a Half . . .

heather-ferrell
Download Presentation

Bell Work

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Bell Work Half of a Half of a Half . . . • Some forms of chemical elements are unstable—that is, they break down into other substances. Like the decay of leftovers in your refrigerator, this breakdown takes place over time. Unlike those leftovers, however, the breakdown of unstable forms of an element progresses in a very orderly way—by decaying into halves.

  2. Bell Work 1. Using your ruler, draw a line 24 cm in length on a sheet of paper. Make a mark at the halfway point (12 cm). 2. Then, divide this 12-cm segment in half, making a mark at 6 cm. Continue in this way, dividing each progressively smaller segment in half (ignoring all of the other segments) until it becomes too small to accurately measure. 3. Now count each progressively smaller half-segment. How many segments did you count?

  3. The History of Life The Fossil Record

  4. Fossils and Ancient Life • Paleontologists are scientists who collect and study fossils. • fossil – preserved remains or evidence of an ancient organism • The fossil record includes information about the structure of organisms, what they ate, what ate them, in what environment they lived, and the order in which they lived.

  5. Significance of the Fossil Record • The fossil record provides evidence about the history of life on Earth. It also shows how different groups of organisms, including species, have changed over time.

  6. The Fossil Record • Over 99% of all species that have lived on Earth have become extinct, which means that the species has died out. • The fossil record provides incomplete information about the history of life.

  7. How Fossils Form • Fossils can be as large as a complete, preserved animal, or as small as a fragment. • Most fossils form in sedimentary rock. • Sedimentary rock forms when exposure to the elements breaks down existing rock into small particles of sand, silt, and clay.

  8. Fossil Formation Water carries small rock particles to lakes and seas.

  9. Fossil Formation Dead organisms are buried by layers of sediment, which forms new rock.

  10. Fossil Formation The preserved remains may be later discovered and studied.

  11. Interpreting Fossil Evidence • Paleontologists determine the age of fossils using relative dating or radioactive dating.

  12. Relative Dating • In relative dating, the age of a fossil is determined by comparing its placement with that of fossils in other layers of rock. • Rock layers form in order by age—the oldest on the bottom, with more recent layers on top.

  13. Relative Dating

  14. Relative Dating • Index fossils are used to compare the relative ages of fossils. • An index fossil is a species that is recognizable and that existed for a short period but had a wide geographic range. • * Relative dating allows paleontologists to estimate a fossil's age compared with that of other fossils.

  15. Radioactive Dating • Scientists use radioactive decay to assign an absolute age to rocks. • Some elements are radioactive and steadily break down into nonradioactive elements.

  16. Radioactive Dating • Radioactive dating is the use of half-lives to determine the age of a sample. • A half-life is the length of time required for half of the radioactive atoms in a sample to decay.

  17. Radioactive Decay

  18. Radioactive Dating • * In radioactive dating, scientists calculate the age of a sample based on the amount of remaining radioactive isotopes it contains.

  19. Carbon-14 • Carbon-14 begins to decay when an organism dies. • Carbon-12 is not radioactive and does not decay. • By comparing the amounts of carbon-14 and carbon-12 in a fossil, researchers can determine when the organism lived.

  20. The Geologic Time Scale • Paleontologists use a scale called the geologic time scale to represent evolutionary time. • * The basic divisions of the geologic time scale are eras and periods.

  21. Geologic Time Scale Figure 17-5 Geologic Time Scale Section 17-1 (millions of years ago) (millions of years ago) Era Period Time (millions of years ago) Era Period Time Era Period Time Permian Carboniferous Devonian Silurian Ordovician Cambrian 290 – 245 360–290 410–360 440–410 505–440 544–505 Quaternary Tertiary Cretaceous Jurassic Triassic 1.8–present 65–1.8 145–65 208–145 245–208 Vendian 650–544

  22. Geologic Time Scale Figure 17-5 Geologic Time Scale Section 17-1 (millions of years ago) (millions of years ago) Era Period Time (millions of years ago) Era Period Time Era Period Time Permian Carboniferous Devonian Silurian Ordovician Cambrian 290 – 245 360–290 410–360 440–410 505–440 544–505 Quaternary Tertiary Cretaceous Jurassic Triassic 1.8–present 65–1.8 145–65 208–145 245–208 Vendian 650–544

  23. Geologic Time Scale Figure 17-5 Geologic Time Scale Section 17-1 (millions of years ago) (millions of years ago) Era Period Time (millions of years ago) Era Period Time Era Period Time Permian Carboniferous Devonian Silurian Ordovician Cambrian 290 – 245 360–290 410–360 440–410 505–440 544–505 Quaternary Tertiary Cretaceous Jurassic Triassic 1.8–present 65–1.8 145–65 208–145 245–208 Vendian 650–544

  24. Cenozoic EraMesozoic EraPaleozoic EraPrecambrian Time First humans Radiation of mammals Firstprokaryotes First land plants First multicellular organisms Accumulation of atmospheric oxygen Firsteukaryotes

More Related