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Year 8 Science — Microorganisms around us

Name the main groups of microorganisms and say what they do for soil, food and crops.

Name: ________________________

  1. 1.Match each microorganism to the job it does for us.

    • Yeast
    • Lactobacillus
    • Rhizobium
    • traps nitrogen from the air for legume plants
    • turns milk into curd
    • makes bread and cake dough rise

  2. 2.Which bacterium ferments milk into curd, feeding on the milk sugar lactose? Give its name.

  3. 3.Manure forms best under certain conditions. Which does the chapter name?

    • a) Freezing temperatures and standing water
    • b) Complete darkness and dry conditions
    • c) An optimal temperature and an appropriate moisture level
    • d) Direct sunlight and dry soil

  4. 4.Microalgae live in water, soil, air and on trees, and make their own food using sunlight. What does the chapter say they release while doing so?

    • a) More than half of the Earth's carbon dioxide
    • b) The nitrogen that legumes take up
    • c) The methane in biogas
    • d) More than half of the Earth's oxygen supply

  5. 5.Why do pickles and murabbas keep for months without going mouldy?

    • a) The high concentration of salt or sugar stops microorganisms growing on them
    • b) They are sealed so tightly that no microorganism can reach them
    • c) Microorganisms cannot live on fruit once it has been cut
    • d) The spices in them kill any microorganism that lands

  6. 6.Sort these by whether the whole living thing is one cell or many.

    Groups: Unicellular · Multicellular

    • Yeast
    • Amoeba
    • Mould
    • Bacteria

  7. 7.Some microorganisms live in hot water springs and snow-cold zones. What does that tell you about them as a group?

    • a) They can live in extreme conditions as well as moderate ones
    • b) They can live at high temperatures but not at low ones
    • c) They live in extreme conditions and cannot survive moderate ones
    • d) They cannot survive anywhere that a plant cannot grow

  8. 8.Why do farmers grow legumes such as beans and peas in rotation with other crops?

    • a) Legumes use less water, so more is left in the soil for the next crop
    • b) Legumes drive away the pests that would attack the next crop
    • c) Legume roots break up hard soil so the next crop can spread its roots
    • d) Rhizobium in their root nodules adds nitrogen to the soil, leaving it healthier for the next crop

Answer key — Year 8 Science — Microorganisms around us

  1. 1. Yeast → makes bread and cake dough rise; Lactobacillus → turns milk into curd; Rhizobium → traps nitrogen from the air for legume plants
  2. 2. lactobacillus
  3. 3. c) An optimal temperature and an appropriate moisture level
  4. 4. d) More than half of the Earth's oxygen supply
  5. 5. a) The high concentration of salt or sugar stops microorganisms growing on them
  6. 6. Bacteria → Unicellular; Amoeba → Unicellular; Yeast → Unicellular; Mould → Multicellular
  7. 7. a) They can live in extreme conditions as well as moderate ones
  8. 8. d) Rhizobium in their root nodules adds nitrogen to the soil, leaving it healthier for the next crop