Micro Organisms Questions and Answers

Q: A common preservative used in jam and pickles is

Correct answer: Sodium benzoateSodium benzoate is the standard chemical preservative for jams, squashes and pickles. It works only in acid conditions, where it converts to benzoic acid and enters the microbial cell, disrupting its metabolism - which is why it suits acidic foods and not others. Salt and sugar preserve too, but osmotically rather than as chemical preservatives.

Q: Which among the following statements is not associated with food preservation?

Correct answer: Decreased shelf lifePreservation exists to increase shelf life, so a decrease is the opposite of what is wanted. The other three describe it correctly: preventing decay, sealing against air and organisms, and keeping food for later use.

Q: In order to take precautionary steps to control dengue, we must take measures to stop the breeding of:

Correct answer: Aedes mosquitoDengue is transmitted by the Aedes mosquito, which breeds in small collections of clean water - tyres, pots, coolers, roof gutters - and bites by day. Control therefore means emptying such containers rather than spraying open water. Anopheles carries malaria.

Q: Which among the following pathogens causes cholera?

Correct answer: BacteriaCholera is caused by Vibrio cholerae, a comma-shaped bacterium spread through water contaminated with faeces. Its toxin makes the gut pour out water, and it is the resulting dehydration, not the organism itself, that kills - which is why oral rehydration is so effective.

Q: The bacteria present in the root nodules of pea are

Correct answer: RhizobiumRhizobium lives in the root nodules of legumes such as pea, gram and beans, fixing atmospheric nitrogen into a form the plant can use; the plant supplies it with sugars in return. That symbiosis is why legumes enrich the soil and why they are used in crop rotation.

Q: What is the shape of an amoeba?

Correct answer: No definite shapeAn amoeba has no fixed shape: it has no cell wall, and its cytoplasm flows into pseudopodia that it uses to move and to engulf food. Its outline is therefore always changing.

Q: Penicillium is a

Correct answer: FungusPenicillium is a mould, that is a filamentous fungus - the blue-green growth seen on stale bread and citrus fruit. Fleming’s observation that it killed the bacteria around it led to penicillin.

Q: Which of the following is a disease caused by protozoans?

Correct answer: MalariaMalaria is caused by the protozoan Plasmodium. Tuberculosis and typhoid are bacterial, and polio is viral.

Q: Which one of the following is not a fungus?

Correct answer: ChickenpoxChickenpox is caused by a virus, varicella-zoster. Bread mould, potato blight and mushrooms are all fungi or fungus-like organisms.

Q: Dead plants and animals in the soil are broken down into humus by the efforts of

Correct answer: bacteria and fungi in the soil.Decomposition is the work of both bacteria and fungi. Fungi are particularly good at breaking down tough materials such as cellulose and lignin, and bacteria complete the process - between them turning dead matter into humus and releasing the nutrients it contains. Viruses play no part.

81.

A common preservative used in jam and pickles is

A.Sodium benzoate
B.Nitric acid
C.Sodium Chloride
D.Copper Sulphate

Answer: A

Correct answer: Sodium benzoate

Sodium benzoate is the standard chemical preservative for jams, squashes and pickles. It works only in acid conditions, where it converts to benzoic acid and enters the microbial cell, disrupting its metabolism - which is why it suits acidic foods and not others. Salt and sugar preserve too, but osmotically rather than as chemical preservatives.

Discuss in Forum

82.

Which among the following statements is not associated with food preservation?

A.Prevention of decay or spoilage
B.Decreased shelf life
C.Air-tight sealing
D.Storage for future use

Answer: B

Correct answer: Decreased shelf life

Preservation exists to increase shelf life, so a decrease is the opposite of what is wanted. The other three describe it correctly: preventing decay, sealing against air and organisms, and keeping food for later use.

Discuss in Forum

83.

In order to take precautionary steps to control dengue, we must take measures to stop the breeding of:

A.Aedes mosquito
B.Fleas
C.Fire ants
D.Anopheles mosquito

Answer: A

Correct answer: Aedes mosquito

Dengue is transmitted by the Aedes mosquito, which breeds in small collections of clean water - tyres, pots, coolers, roof gutters - and bites by day. Control therefore means emptying such containers rather than spraying open water. Anopheles carries malaria.

Discuss in Forum

84.

Which among the following pathogens causes cholera?

A.Bacteria
B.Protozoan
C.Fungus
D.Virus

Answer: A

Correct answer: Bacteria

Cholera is caused by Vibrio cholerae, a comma-shaped bacterium spread through water contaminated with faeces. Its toxin makes the gut pour out water, and it is the resulting dehydration, not the organism itself, that kills - which is why oral rehydration is so effective.

Discuss in Forum

85.

The bacteria present in the root nodules of pea are

A.Coli
B.Plasmodium
C.Rhizobium
D.Penicillin

Answer: C

Correct answer: Rhizobium

Rhizobium lives in the root nodules of legumes such as pea, gram and beans, fixing atmospheric nitrogen into a form the plant can use; the plant supplies it with sugars in return. That symbiosis is why legumes enrich the soil and why they are used in crop rotation.

Discuss in Forum

86.

What is the shape of an amoeba?

A.Spherical
B.Elongated
C.Spiral
D.No definite shape

Answer: D

Correct answer: No definite shape

An amoeba has no fixed shape: it has no cell wall, and its cytoplasm flows into pseudopodia that it uses to move and to engulf food. Its outline is therefore always changing.

Discuss in Forum

87.

Penicillium is a

A.Algae
B.Fungus
C.Bacteria
D.Yeast

Answer: B

Correct answer: Fungus

Penicillium is a mould, that is a filamentous fungus - the blue-green growth seen on stale bread and citrus fruit. Fleming’s observation that it killed the bacteria around it led to penicillin.

Discuss in Forum

88.

Which of the following is a disease caused by protozoans?

A.Tuberculosis
B.Polio
C.Malaria
D.Typhoid

Answer: C

Correct answer: Malaria

Malaria is caused by the protozoan Plasmodium. Tuberculosis and typhoid are bacterial, and polio is viral.

Discuss in Forum

89.

Which one of the following is not a fungus?

A.Bread mould
B.Potato blight
C.Chickenpox
D.Mushroom

Answer: C

Correct answer: Chickenpox

Chickenpox is caused by a virus, varicella-zoster. Bread mould, potato blight and mushrooms are all fungi or fungus-like organisms.

Discuss in Forum

90.

Dead plants and animals in the soil are broken down into humus by the efforts of

A.bacteria and fungi in the soil.
B.Viruses in the soil.
C.bacteria only in the soil.
D.Fungi and viruses in the soil.

Answer: A

Correct answer: bacteria and fungi in the soil.

Decomposition is the work of both bacteria and fungi. Fungi are particularly good at breaking down tough materials such as cellulose and lignin, and bacteria complete the process - between them turning dead matter into humus and releasing the nutrients it contains. Viruses play no part.

Discuss in Forum

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