How helpful traits become more common over many generations

Grade 7 Science Worksheet - Challenge Me

Circle the best answer.

1. Read this first

   Use the table

   Three rounds of an antibiotic on a lab plate (model data). Agar plate diagram, zones: Zone 1: Round 1: antibiotic on the plate | a few small colonies; Zone 2: Round 2: bacteria from those colonies, same antibiotic | many colonies; Zone 3: Round 3: bacteria from the Round 2 colonies, same antibiotic | colonies cover most of the plate. Comparison chart.

   Round	Able to grow with the antibiotic (per 1,000 bacteria)
   Round 1	3
   Round 2	480
   Round 3	910

   Bar graph: x axis Round; y axis Able to grow with the antibiotic (per 1,000), ticks every 200 from 0 to 1000. Bars: Round 1 3; Round 2 480; Round 3 910.

2. 1.

   Ari reads the three plates and the chart together. Which claim fits both?

   • The medicine got weaker, so more bacteria grew
   • Bacteria that could already grow with it became more common
   • The whole group became resistant in Round 2
   • Each bacterium changed itself to resist the antibiotic in Round 1
3. 2.

   The chart shows 3 per 1,000 in Round 1 and 480 per 1,000 in Round 2. Bo asks where the Round 2 resistant bacteria came from. What fits the plates?

   • The bacteria needed to resist it, so they grew resistance
   • The few in Round 1 multiplied and passed the trait on
   • The medicine got weaker in Round 2
   • The trait reached the whole group at once
4. 3.

   Esme plans Round 4 with the same antibiotic. Using the plates and the chart, what will Round 4 most likely show?

   • Fewer grow, since each bacterium slowly loses its resistance over time
   • Most still grow, since resistant bacteria are most of the group
   • Few grow, since bacteria of this kind are stopped by it
   • More grow, since the medicine gets weaker each round
5. 4.

   Dark moths helped in 1895, yet light moths rose after the clean-air laws. Jun asks how that fits natural selection. Which explanation fits?

   • Clean air made light moths appear from nowhere
   • Dark moths turned light when the air cleared, to match the bark
   • A trait helps where it matches the place, and the bark changed
   • The change finished within a single year
6. 5.

   The finches that had young averaged 9.9 mm, but their offspring averaged 9.7 mm. Kira asks why the numbers differ. What explains it?

   • Young differ from each other, so their average lands between groups
   • Each young finch's beak shrank after hatching
   • Finches share one beak depth, so the two averages should match exactly
   • The drought ended, so the trait was undone
7. 6.

   Noah says: "Each finch grew a deeper beak during the drought, so the average beak depth rose." Which flaw fits the chart?

   • Beaks do not grow to fit; deeper-beaked finches had more young
   • The flaw is that beak depth cannot vary, so the average cannot rise
   • No flaw, since each finch changed its beak to fit the large seeds
   • The flaw is that seeds do not matter to a beak
8. 7.

   Pia says: "The plants flowered earlier because the drought made them need to." Which flaw fits the chart?

   • No flaw, since each plant sped up its own flowering to escape the dry weather
   • The flaw is that the drought lasted several years
   • A need does not cause a trait; early-flowering plants had more young
   • The flaw is that the whole group changed in one year
9. 8.

   Ren reads the moth chart for 1959 and 1984. Which claim and reason fit it?

   • Light moths stayed rare; the moths share one color and cannot vary
   • Light moths rose; those matching pale bark had more young
   • Light moths became common in one year; selection is instant
   • Dark moths became light; each moth changed to match the clean bark
10. 9.

    Tala reads the finch chart. Which claim and reason explain the change from 9.2 mm to 9.7 mm?

    • The average rose; each finch strained its beak until it grew deeper
    • The average stayed the same; the finches share one beak depth
    • The average rose; deeper-beaked finches cracked seeds and had more young
    • The average rose; the drought made the beaks of each finch grow deeper
11. 10.

    Zee reads the flowering chart for both sites. Which claim and reason fit it?

    • Flowering stayed the same; the plants share one flowering time
    • Flowering moved earlier; the plants needed to escape the dry weather
    • Flowering moved earlier; each plant sped up its own flowers
    • Flowering moved earlier; early-flowering plants had more young