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Investigating evidence for evolution

Science · Ecosystems & Habitats · ages 12-14

Name ______________________ Date ____________

In sedimentary layers that have not been overturned, fossils in lower layers are generally older than fossils in higher layers.
Circle one: True False
Which process can preserve buried bones as a fossil?
- Bones turn to stone at the instant the animal dies.
- Minerals fill spaces in the bones or replace their material.
- An ordinary rock grows into a bone shape without an organism being present.
What does pentadactyl mean when describing a limb plan?
- The limb has five digits, with several bones making up the limb.
- The whole limb contains five bones.
- Each of the limb's five bones forms a separate finger.
A human arm, bat wing and whale flipper have corresponding bones in a shared arrangement, but different uses. What does this support?
- They inherited the limb plan from a common ancestor.
- They must use their limbs in exactly the same way today.
- Each animal copied the arrangement from another living species.
A dated lower rock layer contains smooth-shelled fossils. A dated higher layer contains ribbed-shelled fossils. The layers have not been overturned. What does this comparison support?
- The higher layer formed first.
- The newer shells must have belonged to more complex organisms than the older shells.
- The forms of life recorded there changed over time.
Related Galapagos finch species share many features but differ in inherited beak traits and geographic distribution. Which explanation fits this evidence?
- Individual birds changed their beaks to suit new food.
- An ancestral population reached the islands and its descendants diverged.
- The species arose independently on the islands and have no common ancestral population.
Whales retain reduced pelvic bones that no longer support walking. Sam says these bones support land ancestry only if they have no use today. Which response fits?
- A reduced ancestral structure can retain another use.
- Any current use rules out ancestry.
- A reduced bone proves that living whales still walk on land like their ancestors.
A classmate says, 'No person lived millions of years ago, so fossils cannot provide evidence of changes in past life.' Which response addresses that reasoning?
- Fossils cannot tell us about events without a witness.
- Every older fossil is a direct ancestor of a living species.
- Scientists can compare dated remains to test past changes without an eyewitness.

Answer key

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

Investigating evidence for evolution W1-mt_ohUnzoI_nx-s1

True · Lower layers were deposited first when the sequence has not been overturned. Their fossils are generally older, without necessarily belonging to simpler organisms.
Minerals fill spaces in the bones or replace their material. · Burial can protect bones. Minerals can then fill their spaces or replace their material. This is one route to fossil preservation, not the only kind of fossil.
The limb has five digits, with several bones making up the limb. · Pentadactyl means five digits. The whole limb contains many bones, including upper-arm, forearm, wrist and digit bones.
They inherited the limb plan from a common ancestor. · Corresponding bones in a shared arrangement are homologous structures. They support common ancestry even when the limbs have different functions.
The forms of life recorded there changed over time. · The older and newer layers record different shell forms. This supports change through time without proving greater complexity or a direct ancestor-descendant relationship.
An ancestral population reached the islands and its descendants diverged. · Shared features and geographic patterns support common ancestry. Isolation and selection acting on inherited differences helped populations diverge across generations.
A reduced ancestral structure can retain another use. · Vestigial means an ancestral function has been lost or reduced, not that a structure must be useless. These bones contribute evidence alongside fossils and other anatomy.
Scientists can compare dated remains to test past changes without an eyewitness. · An eyewitness is not required for evidence about the past. Dated fossil comparisons let scientists test explanations about changes in past life.