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 has new bones
   • 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 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.

   • 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
   • Right: a different job means different 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.

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

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

   • Bird and bat, since their wings share the same forelimb bones
   • Bat and butterfly, since both wings work in flight
   • Bird, bat and butterfly equally, since each wing has the same job
   • Bird and butterfly, since both wings are used for flying
7. 5.

   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.

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

8. 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

9. 6.

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

   • 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
   • The flaw is that chicken and turkey are the same animal
   • No flaw, since a high DNA percent means most traits match
10. 7.

    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 the longest stretch should match 100 percent
    • No flaw, since a close DNA match means that one kind became the other kind
    • 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
11. 8.

    “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
    • The flaw is that fossils in one quarry share an age
    • No flaw, since layers on top formed first
12. 9.

    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?

    • One fish grew limbs during its own life, since Layer 2 has arm-like bones in its fins
    • Fins and limbs formed together, since the layers touch
    • Limbs came from fins, since older layers hold fins and newer ones hold limbs
    • Fins came from limbs, since deeper layers are younger
13. 10.

    Zee reads the DNA chart. Which claim and reason fit best?

    • Neither kind is closer to Kind 5, since a percent says nothing about relatives
    • Kind 6 is closer to Kind 5, since more DNA letters match
    • Kind 7 is closer to Kind 5, since fewer DNA letters match
    • Kind 6 shares 97 percent of body traits with Kind 5, since the percent counts traits