Rock Cycle - Past Life (4)

  • Discovering that "the present is the key to the past."
  • Comparing recent organisms with fossils
  • fossil
  • living
  • past
  • recent
  • Rock Cycle - Past Life (4)
  • hand lens or Swift GH

Students compare living coral, gastropod and bivalves with fossils.

A bivalve shell - notice preservation of shell features


One meaning of the statement "the present is the key to the past," is that knowing about present day organisms can help to identify fossils and to explain their behavior and ecology. The remains of present day organisms are often better preserved than are fossils, so the former contain much more scientific information.

In this lab, students will compare recent and fossil remains, and distinguish their differences.

  1. Explain to the students that the remains of once-living modern organisms have distinct key characteristics. These key characteristics can help you identify fossil examples of the same kind of organism.

    Discuss the key characteristics of "present" day organisms compared to those of the "past." Include items like teeth, bones, bark, and shells. Emphasize to your students that items like blood, skin, hair, and clothes are not found from the "past" (unless mummified).

  2. Instruct the students to observe and draw the specimens of recent organisms. Help them observe details, so that they will be able to compare the fossils and recent specimens. Use a hand lens or Swift GH microscope to observe the specimens.
  3. Students should  examine the fossils, and match each fossil with its recent counterpart. After they make a correct match, have them again draw the fossil.

    Different fossil specimens have gone through different types of fossilization. The characteristics listed below may be slightly different from your specimens.

    SHELL: Recent samples should have ridges, growth lines, and should be whitish, with a hint of color. Fossil samples should be white and embedded into rock; growth lines may be visible.

    GASTROPOD: The recent samples are spiraled and colored. The students should be able to count the spirals. The fossil sample should be whitish, and often reveals the inside of the gastropod.

    CORAL: The recent sample will be full of small holes, which were inhabited by the living coral organisms. Some samples may be colored. The fossils look very rocklike, and show only cross sections of the inside of the coral. 

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