Micro Organisms Questions and Answers

Q: Agar is placed in a petri dish and some soil is sprinkled on the agar. The lid is placed on the petri dish, and it is incubated for two days. After two days, areas of bacteria and fungi are visible on the agar. What is the name for these areas?

Correct answer: ColoniesEach visible patch is a colony - the descendants of a single cell that landed on the agar and multiplied until the mass became visible. Counting colonies is how bacteria are counted, on the assumption that one colony grew from one organism.

Q: The type of microorganism used to make yoghurt is

Correct answer: bacteriaYoghurt is made with bacteria - Lactobacillus bulgaricus and Streptococcus thermophilus - which ferment lactose to lactic acid. The acid coagulates the milk protein and gives yoghurt its texture and its sharp taste.

Q: Spirogyra is a type of

Correct answer: AlgaeSpirogyra is a filamentous green alga of fresh water, named for the spiral chloroplasts that wind through each cell. Being photosynthetic, it makes its own food.

Q: Which of the following diseases can be cured using antibiotics?

Correct answer: TyphoidTyphoid is caused by a bacterium, Salmonella typhi, and so responds to antibiotics. AIDS and dengue are viral and malaria protozoal - antibiotics act on bacterial structures that none of those possess.

Q: Lactobacillus is commonly found in

Correct answer: CurdLactobacillus ferments the lactose of milk to lactic acid, which coagulates the casein and sets the curd. Bread and cake are raised by yeast, a fungus, not by lactobacilli.

Q: Litmus, used as an indicator for acids and bases, is extracted from

Correct answer: LichensLitmus is extracted from lichens, chiefly Roccella species. It turns red in acid and blue in alkali, and was one of the earliest chemical indicators - used long before anyone understood why it worked.

Q: Which organisms are microscopic and dependent on host organisms for reproduction?

Correct answer: VirusesViruses are microscopic and can reproduce only inside a living host cell: they have no ribosomes and no metabolism of their own, so they must use the host’s. Bacteria, protozoa and algae are cells and multiply on their own.

Q: Vaccines are made up of:

Correct answer: Weak microorganismsA vaccine contains the pathogen in a form that cannot cause disease - weakened (attenuated) or killed organisms, or just a part of one such as a surface protein or an inactivated toxin. The immune system responds and retains memory cells, so a later encounter with the real organism is dealt with at once.

Q: Which cannot fix atmospheric nitrogen in the soil?

Correct answer: PenicilliumPenicillium is a mould, and it fixes no nitrogen - it is famous for producing penicillin. Rhizobium fixes nitrogen symbiotically in root nodules, while Azotobacter and Clostridium do so free-living in the soil.

Q: Tooth decay is caused by sugars. What feeds on sugars in the mouth to cause tooth decay?

Correct answer: BacteriaStreptococcus mutans and related bacteria in dental plaque ferment sugars from food and produce acid, and it is the acid that dissolves the enamel. Sugar alone would do nothing without them, which is why brushing - removing the plaque - matters as much as avoiding sweets.

51.

Agar is placed in a petri dish and some soil is sprinkled on the agar. The lid is placed on the petri dish, and it is incubated for two days. After two days, areas of bacteria and fungi are visible on the agar.

What is the name for these areas?

A.Nutrient
B.Antibiotics
C.Microorganisms
D.Colonies

Answer: D

Correct answer: Colonies

Each visible patch is a colony - the descendants of a single cell that landed on the agar and multiplied until the mass became visible. Counting colonies is how bacteria are counted, on the assumption that one colony grew from one organism.

Discuss in Forum

52.

The type of microorganism used to make yoghurt is

A.bacteria
B.virus
C.ringworm
D.fungus

Answer: A

Correct answer: bacteria

Yoghurt is made with bacteria - Lactobacillus bulgaricus and Streptococcus thermophilus - which ferment lactose to lactic acid. The acid coagulates the milk protein and gives yoghurt its texture and its sharp taste.

Discuss in Forum

53.

Spirogyra is a type of

A.Bacteria
B.Virus
C.Algae
D.Fungi

Answer: C

Correct answer: Algae

Spirogyra is a filamentous green alga of fresh water, named for the spiral chloroplasts that wind through each cell. Being photosynthetic, it makes its own food.

Discuss in Forum

54.

Which of the following diseases can be cured using antibiotics?

A.AIDS
B.Dengue
C.Typhoid
D.Malaria

Answer: C

Correct answer: Typhoid

Typhoid is caused by a bacterium, Salmonella typhi, and so responds to antibiotics. AIDS and dengue are viral and malaria protozoal - antibiotics act on bacterial structures that none of those possess.

Discuss in Forum

55.

Lactobacillus is commonly found in

A.Cake
B.Curd
C.Bread
D.All of the above

Answer: B

Correct answer: Curd

Lactobacillus ferments the lactose of milk to lactic acid, which coagulates the casein and sets the curd. Bread and cake are raised by yeast, a fungus, not by lactobacilli.

Discuss in Forum

56.

Litmus, used as an indicator for acids and bases, is extracted from

A.Lichens
B.Virus
C.Plants
D.Bacteria

Answer: A

Correct answer: Lichens

Litmus is extracted from lichens, chiefly Roccella species. It turns red in acid and blue in alkali, and was one of the earliest chemical indicators - used long before anyone understood why it worked.

Discuss in Forum

57.

Which organisms are microscopic and dependent on host organisms for reproduction?

A.Algae
B.Protozoa
C.Viruses
D.Bacteria

Answer: C

Correct answer: Viruses

Viruses are microscopic and can reproduce only inside a living host cell: they have no ribosomes and no metabolism of their own, so they must use the host’s. Bacteria, protozoa and algae are cells and multiply on their own.

Discuss in Forum

58.

Vaccines are made up of:

A.Chemicals
B.Weak microorganisms
C.Viruses
D.Drugs

Answer: B

Correct answer: Weak microorganisms

A vaccine contains the pathogen in a form that cannot cause disease - weakened (attenuated) or killed organisms, or just a part of one such as a surface protein or an inactivated toxin. The immune system responds and retains memory cells, so a later encounter with the real organism is dealt with at once.

Discuss in Forum

59.

Which cannot fix atmospheric nitrogen in the soil?

A.Rhizobium
B.Clostridium
C.Azotobacter
D.Penicillium

Answer: D

Correct answer: Penicillium

Penicillium is a mould, and it fixes no nitrogen - it is famous for producing penicillin. Rhizobium fixes nitrogen symbiotically in root nodules, while Azotobacter and Clostridium do so free-living in the soil.

Discuss in Forum

60.

Tooth decay is caused by sugars.
What feeds on sugars in the mouth to cause tooth decay?

A.Virus
B.Bacteria
C.Fungi
D.Tooth paste

Answer: B

Correct answer: Bacteria

Streptococcus mutans and related bacteria in dental plaque ferment sugars from food and produce acid, and it is the acid that dissolves the enamel. Sugar alone would do nothing without them, which is why brushing - removing the plaque - matters as much as avoiding sweets.

Discuss in Forum

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