Science 7 · Unit 7: Microorganisms in the environment · Cambridge Lower Secondary Science Stage 7

Questions

1. 1. Which item should a gardener NOT put on a compost heap?

   • glass
   • grass cuttings
   • newspaper
   • apple peel
   Check

2. 2. Which three items should not go on a compost heap?

   • glass, apple peel and newspaper
   • metal, grass cuttings and plastic
   • apple peel, grass cuttings and newspaper
   • glass, metal and plastic
   Check

3. 3. Why should plastic not go on a compost heap?

   • It rots too quickly.
   • Decomposers cannot break it down.
   • It feeds the decomposers too much.
   • It makes the compost too wet.
   Check

4. 4. How could you find out if compost contains microorganisms?

   • Look at it without a microscope.
   • Weigh it.
   • Put a little on sterile agar and see if colonies grow.
   • Smell it.
   Check

5. 📖 This question is about a text that students read in the app.

   5. Arun's bags have different mesh sizes. Which organisms can reach the leaves in the 1 cm mesh bag?

   • no organisms
   • only microorganisms
   • only earthworms
   • earthworms, small animals and microorganisms
   Check

6. 📖 This question is about a text that students read in the app.

   6. Which organisms can reach the leaves in the 0.005 mm mesh bag?

   • earthworms only
   • nothing at all
   • earthworms and small animals
   • only microorganisms
   Check

7. 7. Why did Arun cut every leaf piece to 1 cm × 2 cm, and put 50 in each bag?

   • to make it a fair test, with the same amount of leaf in each bag
   • so earthworms could not eat them
   • so the leaves would rot faster
   • so the bags would be heavy
   Check

8. 📖 This question is about a text that students read in the app.

   8. Which of Arun's results is wrong?

   • the October result for the 1 cm mesh bag
   • the December result for the 1 cm mesh bag
   • the June result for both bags
   • the April result for the 0.005 mm mesh bag
   Check

9. 📖 This question is about a text that students read in the app.

   9. In which bag did the largest area of leaves disappear?

   • the 1 cm mesh bag
   • the 0.005 mm mesh bag
   Check

10. 📖 This question is about a text that students read in the app.

    10. Arun predicted that earthworms and other small animals help leaves decay. What is his evidence?

    • No leaf disappeared from either bag.
    • Much more leaf disappeared from the bag that animals could get into.
    • More leaf disappeared from the bag with tiny holes.
    • The same amount disappeared from both bags.
    Check

11. 11. How could the girls estimate the area of mould growing on the bread?

    • Weigh the bread.
    • Place a grid of 1 mm squares over it and count the squares with mould.
    • Measure the temperature.
    • Smell the mould.
    Check

12. 📖 This question is about a text that students read in the app.

    12. Mould on bread at 40 °C covers 14, 5 and 18 mm². Which result is anomalous?

    • 5 mm²
    • 14 mm²
    • none of them
    • 18 mm²
    Check

13. 📖 This question is about a text that students read in the app.

    13. Ignoring the anomalous 5 mm², what is the mean mould area at 40 °C?

    • 12.3 mm²
    • 32 mm²
    • 16 mm²
    • 18 mm²
    Check

14. 📖 This question is about a text that students read in the app.

    14. Mould at 60 °C covers 10, 12 and 13 mm². What is the mean, to one decimal place?

    • 11.6 mm²
    • 12.0 mm²
    • 11.7 mm²
    • 35.0 mm²
    Check

15. 15. Why are the three bread samples at the same temperature not exactly the same?

    • The thermometer was broken.
    • The girls measured them at different temperatures.
    • Mould only grows on one piece.
    • The bread pieces, and the spores landing on them, vary a little.
    Check

16. 📖 This question is about a text that students read in the app.

    16. What can the girls conclude from their results?

    • Mould grows more as the temperature rises to 40 °C, but less at 60 °C.
    • The hotter it is, the more mould grows.
    • Mould grows best at −4 °C.
    • Temperature has no effect.
    Check

17. 17. Why does very little mould grow at −4 °C?

    • There is no light.
    • The bread is too dry.
    • The chemical reactions in its cells are very slow when it is cold.
    • Mould is killed by water.
    Check

18. 18. Why does less mould grow at 60 °C than at 40 °C?

    • The bread is bigger at 60 °C.
    • It is too cold at 60 °C.
    • Very high temperatures stop the reactions in its cells.
    • There is too much water at 60 °C.
    Check