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

The Clues That Show Evolution Happened

Science · Ecosystems & Habitats · ages 12-14
Name ______________________   Date ____________

  1. Fossils found in deeper, older rock layers are usually simpler than fossils found in layers closer to the surface.

    Circle one:   True   False

  2. How do most fossils form?

    • Minerals slowly replace buried bones or shells over a very long time
    • An animal instantly turns to stone the moment it dies
    • Fossils are rocks that were always shaped like animals

  3. What is a pentadactyl limb?

    • A limb that only appears in fish
    • A limb built on a five-digit bone pattern shared by many different animals
    • A limb with no bones at all

  4. A human arm, a bat wing, and a whale flipper all share the same pentadactyl bone pattern, even though they do very different jobs. What does this pattern most likely show?

    • These animals share a common ancestor
    • These animals copied each other's body shape by coincidence
    • Bones only ever come in one possible arrangement

  5. A scientist digs through rock layers and finds simple sea creatures at the bottom, fish in the middle, and land animals near the top. What does this order suggest?

    • The layers formed all at once in no particular order
    • Land animals lived before sea creatures did
    • Life has changed and become more varied over a long span of time

  6. Darwin found many finch species on the Galapagos Islands, each with a beak shaped for a different food source on its island. What does this pattern suggest?

    • Every finch species appeared separately with no connection to the others
    • The finches share an ancestor and changed to fit each island's food
    • All finches everywhere must have identical beaks

  7. A student claims Darwin's finches on different islands must be totally unrelated species that appeared separately, since their beaks look so different. What evidence best challenges this claim?

    • The finches share many body features typical of a common ancestor; beak differences are small adaptations, not signs of separate origins
    • Islands cannot support finches, so this evidence doesn't apply
    • The student is correct, different beak shapes always mean unrelated species

  8. A classmate says, 'Nobody has ever watched one species turn into another, so fossils can't really prove evolution happened.' What's wrong with that argument?

    • The classmate is right, fossils prove nothing about change over time
    • Fossils only ever show animals that are still alive today
    • The fossil record lets scientists compare life across millions of years, showing change even though no one watched it happen directly
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Answer key

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

The Clues That Show Evolution Happened W1-mt_ohUnzoI_nx-s1

  1. True · Rock layers build up over time, so deeper layers are older, and the fossils in them tend to be simpler forms of life.
  2. Minerals slowly replace buried bones or shells over a very long time · Fossils usually form when a dead organism gets buried in sediment and minerals slowly replace its hard parts over thousands of years.
  3. A limb built on a five-digit bone pattern shared by many different animals · Pentadactyl means 'five digits.' Humans, bats, and whales all have limbs built on this same basic bone plan.
  4. These animals share a common ancestor · Shared structures built on the same underlying pattern, even when used differently, are strong evidence of a shared ancestor.
  5. Life has changed and become more varied over a long span of time · Since deeper layers are older, this order shows life becoming more varied over time, evidence that species change.
  6. The finches share an ancestor and changed to fit each island's food · Related species that differ slightly between nearby islands usually share a common ancestor that adapted differently in each place.
  7. The finches share many body features typical of a common ancestor; beak differences are small adaptations, not signs of separate origins · Small adaptive differences layered on top of many shared features point to one ancestor species branching apart, not several unrelated origins.
  8. The fossil record lets scientists compare life across millions of years, showing change even though no one watched it happen directly · Evidence doesn't require a direct eyewitness. Comparing ordered fossil layers across huge spans of time reveals change just as clearly.
Worksheet · LightMySky