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8th grade · Science · Unit 7 of 7

Earth's History & Fossils

Rock strata, the geologic time scale and evidence of evolution.

What your child practices

Practices how rock layers are used to build Earth's 4.6-billion-year history, patterns in the fossil record, and anatomical and embryo evidence that living things share ancestors.

Alaska content standards learning standard: MS-ESS1-4; MS-LS4-1; MS-LS4-2 · rock strata and Earth's history, the fossil record, and anatomical evidence of common ancestry

How we explain it

Children can open this short lesson before they practice.

  1. Rock layers and fossils order Earth’s 4.6-billion-year history; lower layers are older.
  2. Most of that history is the Precambrian. We live in the Cenozoic Era.
  3. Homologous structures show that living things share ancestors.

Example: In which era do we live today? The eras go Paleozoic, Mesozoic, Cenozoic. The latest is the Cenozoic. Answer: the Cenozoic Era

Earth's History & Fossils in Alaska

In the Alaska content standards, this is unit 7 of 7 in 8th grade Science, after Natural Selection.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Alaska Department of Education and Early Development

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    A rock layer cutting across other layers is…

    • impossible
    • the same age
    • younger than the layers it cuts
    • older than all of them

  2. Question 2

    Which era is called the Age of Dinosaurs?

    • Cenozoic
    • Paleozoic
    • Precambrian
    • Mesozoic

  3. Question 3

    The law of superposition says that in undisturbed rock layers…

    • all layers are the same age
    • the oldest layers are on top
    • layers form sideways
    • the oldest layers are at the bottom

  4. Question 4

    We live in the…

    • Mesozoic Era
    • Paleozoic Era
    • Cenozoic Era
    • Precambrian

  5. Question 5

    A human arm, bat wing and whale flipper have similar bones. This suggests…

    • bones come from food
    • they are the same species
    • it's a coincidence
    • they share a common ancestor

  6. Question 6

    Comparing embryos of fish, birds and humans shows…

    • no similarities
    • similar early stages, suggesting relatedness
    • they're the same species
    • embryos don't change

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