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Grade 8 Science — Microorganisms around us

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

Name: ________________________

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

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

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

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

  3. 3.Sort these microorganisms by the group the chapter puts them in.

    Groups: Protozoa · Fungi · Algae

    • Yeast
    • Paramecium
    • Amoeba
    • Spirulina
    • Bread mold

  4. 4.Fruit and vegetable peels are buried in a pot of garden soil. Three weeks later they have become a dark crumbly material. What is it, and what made it?

    • a) Manure, made by the soil dissolving the peels
    • b) Charcoal, made by the peels being pressed under the soil
    • c) Compost, made by the peels drying out in the heat
    • d) Manure, made by fungi and bacteria breaking the peels down

  5. 5.Bacteria and fungi living without oxygen can break down plant and animal waste and release a mixture of gases. What is that mixture called, and what is it mainly?

    • a) Marsh gas, mainly carbon monoxide
    • b) Biogas, mainly carbon dioxide with a high proportion of methane
    • c) Manure gas, mainly hydrogen
    • d) Biogas, mainly oxygen with a little nitrogen

  6. 6.Where does the chapter say microorganisms can be found?

    • a) In water, in soil, in air, and inside the bodies of plants and animals
    • b) In soil and air, but not inside living bodies
    • c) In water and soil, but not in air
    • d) Chiefly in food that has been left out to rot

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

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

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

Answer key — Grade 8 Science — Microorganisms around us

  1. 1. a) An optimal temperature and an appropriate moisture level
  2. 2. Yeast → makes bread and cake dough rise; Lactobacillus → turns milk into curd; Rhizobium → traps nitrogen from the air for legume plants
  3. 3. Amoeba → Protozoa; Paramecium → Protozoa; Bread mold → Fungi; Yeast → Fungi; Spirulina → Algae
  4. 4. d) Manure, made by fungi and bacteria breaking the peels down
  5. 5. b) Biogas, mainly carbon dioxide with a high proportion of methane
  6. 6. a) In water, in soil, in air, and inside the bodies of plants and animals
  7. 7. d) More than half of the Earth's oxygen supply
  8. 8. c) They can live in extreme conditions as well as moderate ones