Clues that living things share ancestors

Grade 7 Science Worksheet - Challenge Me

Circle the best answer.

2. 1.

   Ari reads the whale chart. Which claim uses both the fossil rows and the flipper row?

   • Fossil limbs shrink in order, and the flipper keeps the leg bones
   • Fossil limbs shrink in order, and a living land animal became a whale
   • Fossil limbs shrink in order, and the flipper has new bones
   • Fossil limbs grow in order, and the flipper keeps the leg bones
3. 2.

   Bo says a flipper cannot be related to a leg, since one swims and one walks. What does the chart show?

   Use the picture in question 1.

   • Right: a different job means different bones
   • Wrong: flippers and legs look alike, so the animals must be close relatives
   • Right: fossils cannot show how limbs change
   • Wrong: fossils go from legs to paddles, and the flipper keeps leg bones
4. 3.

   Esme asks why a swimming flipper and a walking cat leg share bones. Which reason fits the chart?

   Use the picture in question 1.

   • A living cat turned into a whale, so they share bones
   • Both limbs move the animal about, so the two limbs must have the same bones in them
   • Both limbs look alike, so the animals are close relatives
   • Both came from a shared ancestor's limb, as the fossils show limbs changing
6. 4.

   The bird wing and butterfly wing both fly, yet Jun says they are not close relatives. Which explanation fits the chart?

   • Same job, so the animals share a recent ancestor
   • Same job, different build, so the wings evolved separately
   • Different build, so the wings must do different jobs
   • A living butterfly came from a living bird, since both of them fly
7. 5.

   Kira reads the wing chart. Which two animals does it link most closely, and why?

   Use the picture in question 4.

   • Bird and butterfly, since both wings are used for flying
   • Bat and butterfly, since both wings work in flight
   • Bird and bat, since their wings share the same forelimb bones
   • Bird, bat and butterfly equally, since each wing has the same job
8. 6.

   Luz reads two results on the wing chart, the job and the bones. Which is better evidence of a shared ancestor?

   Use the picture in question 4.

   • Neither, since a chart cannot show ancestry
   • The job, since animals that fly share a recent common ancestor
   • The bones, since matching parts come from a shared ancestor
   • The job, since bones follow the job

9. Read this first

   Use the table

   Three stretches of DNA that chicken and turkey both have (real data: Dalloul et al. 2010, PLoS Biology; percents are about) (real data: Dalloul et al. 2010, PLoS Biology). Comparison chart.

   DNA stretch	Length (letters)	Chicken and turkey match (percent)
   CR1_B	2,000	91
   Birddawg_I	3,600	89
   Galluhop	1,200	91

10. 7.

    Milo says: Chicken and turkey match in 91 percent of their body traits. What is the flaw?

    • No flaw, since a high DNA percent means most traits match
    • The flaw is that chicken and turkey are the same animal
    • The 91 percent counts matching DNA letters in one stretch, not body traits
    • The flaw is that 91 percent is too low to show any link
11. 8.

    Noah says: Chicken and turkey match about 91 percent in DNA, so a chicken turned into a turkey. What is the flaw?

    • The flaw is that DNA cannot show how kinds are related
    • A DNA match shows a shared ancestor, not one kind turning into the other
    • The flaw is that the longest stretch should match 100 percent
    • No flaw, since a close DNA match means that one kind became the other kind
12. 9.

    “layers never moved” Pia says: The moth wing print is in Layer 1, the top layer, so it is the oldest fossil. What is the flaw?

    • The top layer is the youngest, so the moth wing print is the youngest
    • The flaw is that the crab shell should be the youngest
    • No flaw, since layers on top formed first
    • The flaw is that fossils in one quarry share an age
13. 10.

    Three rock layers (model data). Rock-layers diagram, layers never moved, top to bottom. Tala reads the rock layers. Which claim and reason fit best?

    • Fins came from limbs, since deeper layers are younger
    • Fins and limbs formed together, since the layers touch
    • Limbs came from fins, since older layers hold fins and newer ones hold limbs
    • One fish grew limbs during its own life, since Layer 2 has arm-like bones in its fins