Reconstructing Ancient Ecosystems · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Reading Bones and Teeth Like a Diary

Science · Dinosaurs & Paleontology · ages 12-14
Name ______________________   Date ____________

  1. What does each ring in a bone cross-section usually represent?

    • One day of growth
    • One year of growth
    • One season of growth

  2. What does it mean when the oxygen isotope level changes between layers in a dinosaur's tooth?

    • The dinosaur drank from a different water source
    • The dinosaur got sick
    • The tooth started decaying

  3. One piece of evidence, like a single isotope reading, is always enough to prove a dinosaur migrated.

    Circle one:   True   False

  4. This chart shows the oxygen isotope level in tooth layers from two seasons. What does the big jump between spring and autumn most likely suggest?

    Springteeth4Autumnteeth10
    • The dinosaur travelled to a different water source
    • The dinosaur ate different plants
    • The tooth was measured wrong

  5. This bone slice shows growth rings. About how many years old was this dinosaur?

    • 6
    • 10
    • 8

  6. Why do palaeontologists check coprolites and fossil plant beds together, rather than trusting one alone?

    • Because fossil plants are always more reliable than coprolites
    • Because agreement between independent clues makes the conclusion more trustworthy
    • Because coprolites are hard to find

  7. A fossil bone shows 12 growth rings. The last 2 rings are squeezed close together, showing slower growth. How many years did the animal spend growing at its normal, faster rate?

    Answer: ______________

  8. A scientist finds only one shifting isotope reading in a tooth and announces the dinosaur definitely migrated hundreds of kilometres every year. What is the problem with this claim?

    • Teeth do not contain isotopes
    • Isotope readings can never be trusted
    • A single clue alone cannot rule out other explanations, like a diet change
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Reading Bones and Teeth Like a Diary W1-mt_8_BxtNDrLZ-s1

  1. One year of growth · Like tree rings, each ring in a fossil bone slice marks about one year of the animal's growth.
  2. The dinosaur drank from a different water source · Oxygen isotope levels come from drinking water, and water differs by location, so a change usually means the animal moved somewhere new.
  3. False · Palaeontologists look for multiple independent clues that agree before trusting a conclusion like migration.
  4. The dinosaur travelled to a different water source · A sharp change in isotope level between seasonal layers usually points to the animal drinking from a new location, a sign of migration.
  5. 8 · Count each ring as one year: there are eight rings, so the animal was about eight years old.
  6. Because agreement between independent clues makes the conclusion more trustworthy · When separate kinds of evidence point to the same answer, scientists can trust the conclusion more than if they only had one clue.
  7. 10 · Twelve rings total, minus the last two slow-growth rings, leaves ten years of faster growth.
  8. A single clue alone cannot rule out other explanations, like a diet change · Other things besides migration, such as a change in diet, can also shift isotope readings, so one clue alone is not enough proof.
Worksheet · LightMySky