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8th grade · Science · Unit 8 of 11

Earth's History

Rock layers, the fossil record and common ancestors.

What your child practices

Practices using rock strata to organize Earth's 4.6-billion-year history, reading patterns in the fossil record, and comparing body structures for evidence of common ancestry, with the rock layers and sea fossils of New York's gorges as examples.

New York State Learning 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. Law of superposition: in undisturbed rock layers, the oldest are at the bottom.
  2. The fossil record shows that life on Earth has changed over time.
  3. Similar bones in a human arm, bat wing and whale flipper suggest a common ancestor.

Example: In undisturbed rock layers, where are the oldest layers? Layers settle one on top of another. The first ones are underneath. Answer: at the bottom

Earth's History in New York

In the New York State Learning Standards, this is unit 8 of 11 in 8th grade Science, after Natural Selection and before Space Systems.

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: New York State Education Department (NYSED)

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

    In the rock walls of a New York gorge, the lowest layers are usually…

    • the youngest
    • all the same age
    • made last
    • the oldest

  2. Question 2

    Homologous structures are…

    • made of rock
    • similar body parts from a common ancestor
    • identical in every species
    • parts with no use

  3. Question 3

    The Finger Lakes and many New York valleys were shaped during the most recent…

    • Bronze Age
    • age of the dinosaurs
    • Cambrian explosion
    • Ice Age

  4. Question 4

    The geologic time scale divides Earth's history by…

    • calendar years
    • major events in the rock and fossil record
    • presidents
    • seasons

  5. Question 5

    Most of Earth's history took place in the…

    • Precambrian
    • Cenozoic
    • Mesozoic
    • Jurassic

  6. Question 6

    The fossil record shows that…

    • life has never changed
    • life on Earth has changed over time
    • fossils are recent
    • all species lived at once

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