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← The Invisible Living World: Beyond Our Naked Eye

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Lesson 9 of 10

Track quiz

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7 min

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Before the questions, here are the seven rules this track worked with.

The Invisible Living World — seven rules, one per lesson, as the labs use them
IdeaThe rule, as the lab applies it
A world below the eyeA microscope lens makes a thing look bigger. Size seen = real size × power. An eye can see about 0.1 mm or more. Anything smaller needs a lens.
Four kindsBacteria and protozoa are single cells. A fungus is one cell (yeast) or many threads (mould). A virus is not a cell. It multiplies only inside a host.
Where they liveMicrobes live in water, soil, air, food and inside living things. Some live in hot springs and in snow.
The useful onesYeast needs sugar, water and warmth. Then it makes carbon dioxide gas. The gas fills a balloon. It turns lime water milky.
When food spoilsMicrobes grow on food. Warmth and moisture make them grow faster. Cold makes them grow slower. It does not kill most of them.
Helps or harmsMany microbes help us. Some harm us or our food. Judge a microbe by what it does for us where it is.
Keeping them from growingA lot of salt or sugar stops most microbes growing. A little does not.

A microbe is 0.005 mm across. How big does it look through a ×100 lens?

  • 0.05 mm
  • 5 mm
  • 0.5 mm

A microbe looks 0.05 mm through a ×10 lens. Can an eye see it?

  • No, it is less than 0.1 mm
  • Yes, any lens makes it clear
  • Yes, it is bigger than before

A clue card says: not a cell, multiplies only inside a host. Which kind is it?

  • A protozoan
  • A fungus
  • A virus

Yeast makes dough rise. Which kind of microbe is yeast?

  • A fungus that lives as one cell
  • A virus that lives in dough
  • A protozoan that swims in dough

A drop of pond water shows Amoeba. Which kind is it?

  • A bacterium
  • A protozoan
  • A virus

Warm sugar solution with no yeast has a balloon on top. What happens?

  • The balloon fills slowly
  • The balloon stays flat
  • The balloon fills fast

Curd sets in a warm bowl of milk, not a cold one. Why?

  • Cold milk has no bacteria in it
  • Warm milk has no water in it
  • The curd bacteria grow well when it is warm

Two cut mango slices: one on a shelf, one in a fridge. Which gets mould first?

  • The one on the shelf
  • The one in the fridge
  • Both at the same time

A farmer grows beans and adds no nitrogen fertiliser. Why can she?

  • Beans do not need nitrogen
  • Bacteria in the roots trap nitrogen from the air
  • Beans get nitrogen from the sun

Which helps keep microbes from growing in a jar of pickle?

  • The jar is too small
  • A little salt kills them
  • A lot of salt stops their growth

Every rule here is one you tried. Now open your NCERT book. Meet the same ideas in its questions.

Some microbes make people ill. Next is Health: The Ultimate Treasure. It tells how the body fights back.

Reveal every answer to finish this lesson.