How helpful traits become more common over many generations

Grade 7 Science Worksheet

Circle the best answer.

1. 1.

   Light moths rose from 6 to 30 per 100 as clean-air laws lightened the bark. Bo predicts the next years if the bark stays light. What fits?

   • Back to 6 per 100, since moths change color each year
   • 30 per 100, since the moths share one color
   • More than 30 per 100, since matching moths have more young
   • 100 per 100 by next year, in a single step
2. 2.

   Esme spreads bacteria from the 3 colonies on Plate 2 onto a new plate with the same antibiotic. What will Plate 3 most likely show?

   • Many colonies, since the bacteria became resistant when they met it
   • Many colonies, since the 3 colonies came from resistant bacteria
   • No growth, since the antibiotic stops bacteria of this kind
   • Many colonies, since the medicine became weaker over time
3. 3.

   Jun reads the moth chart. From 1959 to 1984, light moths went from 6 to 30 per 100 as trees regained their pale look. What explains it?

   • The cleaner air made the moths grow lighter
   • Dark moths turned light to match the bark
   • The whole group switched to light in one year
   • Light moths matched the bark, so more survived and had young
4. 4.

   Kira reads the finch chart. After the wet year, the average beak depth fell from 9.4 mm to 9.1 mm. What explains it?

   • The wet weather made the beaks grow smaller
   • Each finch's beak shrank to fit the small seeds
   • The whole group had smaller beaks after one season
   • Small-beaked finches had more young, so the average fell
5. 5.

   Lab plates with an antibiotic (model data). On Plate 2 the antibiotic stopped most growth, but 3 colonies grew. Luz explains the 3 colonies. Which explanation fits?

   • The bacteria changed to resist it when it touched them
   • The medicine wore off in those three spots
   • The bacteria were alike, so the medicine missed three spots
   • A few bacteria in the group could already grow with it
6. 6.

   Milo reads that farmers saved seeds from wild cabbage plants with the biggest flower buds and replanted them, year after year. Which kind of selection is this?

   • Natural selection: the weather chose which plants made seeds
   • Artificial selection: the plants grew bigger buds on purpose
   • Artificial selection: people chose which plants made seeds
   • Natural selection: the plants changed to suit the farm
7. 7.

   Noah reads that broccoli and kale both came from one wild cabbage plant. How did two different vegetables come from it?

   • The plants needed bigger leaves, so leaves grew bigger
   • Each wild plant changed its leaves to suit farm soil
   • People chose plants with the flowers or leaves they wanted, over generations
   • One planting made the new vegetables at once
8. 8.

   Ren compares the two rows of the moth chart. How many more light moths per 100 were there in 1984 than in 1959?

   • 36 more per 100
   • 24 more per 100
   • 30 more per 100
   • 6 more per 100
9. 9.

   Tala compares the finch generations after the wet year. How did the average beak depth change from Generation 1 to Generation 2?

   • 3.0 mm shallower
   • 0.3 mm deeper
   • 0.7 mm shallower
   • 0.3 mm shallower
10. 10.

    Zee counts colonies on two plates with the same antibiotic. How many times as many colonies grew on Plate 3 as on Plate 2?

    • 50 times as many
    • 5 times as many
    • 450 times as many
    • 147 times as many