Useful Microorganisms — Homi Bhabha Class 6 Biology MCQs with Solutions
Free Homi Bhabha Class 6 Biology Useful Microorganisms MCQs with step-by-step solutions (10 questions). Part of Cell & Microorganisms. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Useful Microorganisms · easy · theory
Very tiny living things that can be seen only through a microscope are called:
A. Minerals
B. Insects
C. Machines
D. Microorganisms ✓ Correct
Solution: Microorganisms are living things too small to be seen with the naked eye.
Q2 — Useful Microorganisms · easy · theory
Which microorganism is used in a bakery to make bread dough rise?
A. Earthworm
B. Yeast ✓ Correct
C. Housefly
D. Spider
Solution: Yeast makes dough rise and gives bread its soft, spongy texture.
Q3 — Useful Microorganisms · easy · theory
Milk is changed into curd (dahi) with the help of:
A. Bacteria ✓ Correct
B. Sand
C. Sugar
D. Salt
Solution: Helpful bacteria turn milk into curd.
Q4 — Useful Microorganisms · easy · theory
Microorganisms that break down dead plants and animals and keep the surroundings clean are called:
A. Decomposers ✓ Correct
B. Hunters
C. Producers
D. Predators
Solution: Decomposers rot away dead matter and clean up the environment.
Q5 — Useful Microorganisms · medium · theory
When yeast is added to dough, it releases a gas that makes the dough rise. That gas is:
A. Hydrogen
B. Oxygen (O₂)
C. Carbon dioxide (CO₂) ✓ Correct
D. Nitrogen
Solution: Yeast gives out carbon dioxide (CO₂), whose bubbles make the dough puff up.
Q6 — Useful Microorganisms · medium · theory
The medicine penicillin, used to fight illness, is obtained from a:
A. rock
B. fungus (mould) ✓ Correct
C. green plant
D. fish
Solution: Penicillin comes from a mould (a type of fungus) and is used to treat infections.
Q7 — Useful Microorganisms · medium · theory
Bacteria living in the roots of pulse (bean) plants make the soil more fertile by adding:
A. nitrogen ✓ Correct
B. plastic
C. salt
D. sand
Solution: These root bacteria add nitrogen to the soil, which helps plants grow well.
Q8 — Useful Microorganisms · medium · theory
Dead leaves and kitchen waste are turned into useful manure (compost) mainly by:
A. microorganisms ✓ Correct
B. magnets
C. plastic bags
D. sunlight only
Solution: Microorganisms rot the waste and change it into compost that enriches the soil.
Q9 — Useful Microorganisms · hard · theory
Idli and dosa batter turns soft and spongy before cooking because microorganisms cause:
A. melting
B. freezing
C. rusting
D. fermentation ✓ Correct
Solution: Microorganisms ferment the batter, releasing gas that makes it soft and spongy.
Q10 — Useful Microorganisms · hard · theory
Which statement about microorganisms is correct?
A. All microorganisms cause disease
B. Microorganisms are non-living
C. Not all microorganisms are harmful; many are useful to us ✓ Correct
D. Microorganisms can be seen easily with bare eyes
Solution: Many microorganisms are helpful, for example in making curd, bread and medicines.