Microbes — Homi Bhabha Exam Biology MCQs with Solutions
Free Homi Bhabha Exam Biology Microbes MCQs with step-by-step solutions (10 questions). Part of Classification of Living Organisms. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Microbes · medium · theory
Organisms too small to be seen without a microscope are called:
A. vertebrates
B. microorganisms (microbes) ✓ Correct
C. mammals
D. angiosperms
Solution: Microorganisms are tiny living things visible only under a microscope.
Q2 — Microbes · medium · theory
Which of the following is used in the formation of curd from milk?
A. a fern
B. an alga
C. Lactobacillus bacteria ✓ Correct
D. a virus
Solution: Lactobacillus bacteria ferment milk sugar into lactic acid, forming curd.
Q3 — Microbes · hard · theory
A microbe that can reproduce only inside a living host cell is a:
A. fungus
B. protozoan
C. virus ✓ Correct
D. bacterium
Solution: Viruses are non-living outside a host and can multiply only inside a living cell.
Q4 — Microbes · medium · theory
Yeast is a microorganism used in the baking of bread because it produces:
A. nitrogen gas
B. oxygen gas
C. hydrogen gas
D. carbon dioxide gas ✓ Correct
Solution: Yeast ferments sugars, releasing CO₂ that makes the dough rise.
Q5 — Microbes · hard · theory
The antibiotic penicillin is obtained from a:
A. protozoan
B. green plant
C. virus
D. fungus (Penicillium) ✓ Correct
Solution: Penicillin, the first antibiotic, is produced by the mould Penicillium.
Q6 — Microbes · medium · theory
Which disease is caused by a protozoan and spread by mosquitoes?
A. Tuberculosis
B. Tetanus
C. Malaria ✓ Correct
D. Common cold
Solution: Malaria is caused by the protozoan Plasmodium, transmitted by the female Anopheles mosquito.
Q7 — Microbes · hard · theory
Nitrogen-fixing bacteria such as Rhizobium, found in the root nodules of legumes, help by:
A. producing oxygen
B. converting atmospheric nitrogen into a usable form ✓ Correct
C. destroying the plant
D. causing disease
Solution: Rhizobium fixes atmospheric nitrogen into compounds plants can absorb, improving soil fertility.
Q8 — Microbes · medium · theory
Microorganisms that break down dead plants and animals, returning nutrients to the soil, are called:
A. herbivores
B. decomposers ✓ Correct
C. producers
D. predators
Solution: Decomposers (many bacteria and fungi) recycle nutrients by breaking down dead matter.
Q9 — Microbes · hard · theory
Which of the following is a HARMFUL activity of microorganisms?
A. Fixing nitrogen in soil
B. Making curd
C. Producing antibiotics
D. Causing food to spoil and diseases to spread ✓ Correct
Solution: Some microbes spoil food and cause diseases, which are their harmful effects.
Q10 — Microbes · medium · theory
The main groups of microorganisms are bacteria, fungi, protozoa, some algae and:
A. ferns
B. mammals
C. viruses ✓ Correct
D. insects
Solution: Viruses are included among microorganisms along with bacteria, fungi, protozoa and some algae.