Year 9 Science — Microorganisms around us

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

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

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

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

4.How do viruses differ from the other microorganisms in this chapter?

• a) They are acellular, and multiply after entering a living cell
• b) They are made of many cells rather than one
• c) They are large enough to be seen with the naked eye
• d) They make their own food using sunlight

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

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

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

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

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

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