Judge a biology claim: evidence, reasoning and reliable sources

Grade 9 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   A study found 3 plants with music grew 2 cm taller than 3 plants without. The claim: "Music makes plants grow." What is the problem, Bo asks?

   • Music has no effect on any living thing
   • No problem, since the music plants were taller
   • Plants cannot hear, so no test was needed
   • Too few plants, so a 2 cm gap could be chance
2. 2.

   A survey found more frogs and more insects in gardens near a pond. Esme's friend claims the frogs attract the insects. What is the problem?

   • Frogs attract insects, since both are higher
   • It is a link from a survey; the pond could explain both
   • There were fewer frogs near the pond
   • Insects attract the frogs, which settles the question for good

3. Read this first

   Use this

   Two studies (invented examples). Study A: 10 plants, no control group, found that compost helped. Study B: 200 plants with a control group found no difference.

4. 3.

   Jun finds two compost studies that disagree. What is the best conclusion?

   • Weigh B more, since it is larger and controlled, and test again
   • Average the two studies' numbers together
   • Throw out both studies, since studies that disagree are both wrong
   • Trust A, since it found an effect
5. 4.

   Two labs ran the same yeast test. Lab 1 found more gas in warm water; Lab 2 found no difference. What should scientists do, Kira asks?

   • Decide that yeast tests are not worth trusting, in this lab or any other
   • Pick the lab whose result they like better
   • Repeat the test, compare methods and see which result replicates
   • Keep Lab 1's result, since it was reported first
6. 5.

   A blog says mold grows faster in the fridge, based on one slice. Luz's class data on 20 slices show the opposite. Which should Luz trust?

   • Neither one, since mold grows far too randomly for anyone to study it
   • The blog, since one clear slice is enough
   • The blog, since it is published online
   • The class data, since they use more slices and a clear comparison

7. Mean height after 21 days (example data)

   Group	Plants	Mean height (cm)
   with plant food	10	21
   without plant food	10	15

8. 6.

   Milo's claim: "Plant food makes plants grow twice as tall." Which revised claim fits the data best?

   • Plant food doubles the height of bean plants
   • Plant food helped these bean plants grow about 6 cm taller on average
   • Plant food had no effect on height
   • Plant food makes any plant grow taller

9. Bean seeds sprouted by day 5, 20 seeds each (example data)

   Seeds	Sprouted
   soaked overnight	18
   not soaked	11

10. 7.

    Noah's claim: "Soaking makes seeds sprout." Which revised claim fits the data best?

    • Soaking makes any seed sprout within 5 days
    • Unsoaked seeds cannot sprout
    • Soaked seeds sprouted sooner because the water made them heavier
    • By day 5, more soaked bean seeds had sprouted than unsoaked ones

11. Use this

    Two sources (invented examples). A: a shop page selling a plant spray shows 2 plants: sprayed 30 cm, unsprayed 20 cm. B: a university test of 60 plants found both groups averaged 22 cm.

12. 8.

    Ren compares a shop page and a university test of the same plant spray. Which conclusion is best?

    • The larger test, from a source with nothing to sell, shows no effect
    • The spray works, since the shop's photo clearly shows a taller sprayed plant
    • The spray works, since 30 cm beats 20 cm
    • The two count equally, since both show plants

13. Use this

    Two sources (invented examples). A: a government science page, reviewed in 2025, with references, says plants need light to make their food. B: an unsigned 2008 blog says plants given sugar water need no light.

14. 9.

    Tala finds two pages about what plants need. Which is more reliable, and why?

    • Neither, since both are websites
    • B, since its idea is more surprising and new than the government page
    • A, since it is dated, reviewed and backed by references
    • B, since it has been online longer

15. Use this

    Two sources (invented examples). A: a peer-reviewed study of 300 seeds found salt water lowered sprouting. B: a comment says, "My seeds sprouted fine in salty soil!"

16. 10.

    Zee reads a study and a comment about salt and seeds. Which should Zee trust more?

    • Both equally, since each one has a point
    • The comment, since it is a real person's own experience with salty soil
    • The study, since it tested many seeds and experts checked it
    • The comment, since one success disproves the study