CBSE Questions for Class 8 Biology Microorganisms Friend And Foe Quiz 5 - MCQExams.com

Mosaic of tobacco is caused by
  • Bacteria
  • Virus
  • Fungus
  • All of the above
Pasteurization means
  • Vaccination for a baby against small pox
  • Sterilization in steam cooker at 100$$^o$$C for 10 minutes
  • Heating milk or other liquids to 60$$^o$$C to 70$$^o$$C for short duration
  • A technique of curing people bitten by mad dogs
Choose the fermented food from the following.
  • Wine
  • Fresh juice
  • Milk
  • None of these
A carrier of infection is the one in which 
  • Large scale infection occurs
  • The pathogen resides without producing disease
  • The pathogen passes its sexual phase
  • The pathogen passes its asexual phase
Billions of microorganisms live inside or outside the human body.
  • True
  • False
Which of the following disease is caused by a fungus?
  • Small pox
  • Tuberculosis
  • Cancer
  • Black rust of wheat
Identify a fungus with medicinal importance.
  • Penicillium
  • Cercospora
  • Agaricus
  • Saccharomyces
Food is preserved at low temperature because 
  • Bacterial attack is minimised
  • For easy cooking
  • For easy digestion
  • All the above
Match List I with List II and select the correct answer.
List-IList-II
a. Root rot of tomato$$1$$. Virus
b. Leaf curl of tobacco$$2$$. Bacterium
c. Leaf blight of banana$$3$$. Nematode
d. Red rust of tea$$4$$. Alga
  • A-$$1$$, B-$$3$$, C-$$4$$, D-$$2$$
  • A-$$3$$, B-$$1$$, C-$$2$$, D-$$4$$
  • A-$$1$$, B-$$3$$, C-$$2$$, D-$$4$$
  • A-$$3$$, B-$$1$$, C-$$4$$, D-$$2$$
Antibiotics are
  • Drugs to kill viruses
  • Antimicrobial agents
  • Anti-psychotic agents
  • Bacteria that fix nitrogen
Lactobacillus mediated change of milk to curd occurs due to
  • Coagulation and partial digestion of milk fats
  • Coagulation and partial digestion of milk proteins
  • Coagulation of milk proteins and complete digestion of milk fats
  • Coagulation of milk fats and complete digestion of proteins
Microbes are present in
  • Soil
  • Polluted water
  • Thermal vents
  • All of the above
Why do antibiotics kill bacteria but not viruses? 
  • Antibiotics stimulate the immune system against bacteria but not viruses.
  • Viruses have a ways of blocking antibiotics.
  • Viruses are too small to be affected by antibiotics.
  • Viruses do not have a metabolism.
Which of the following is a partial root parasite?
  • Sandal wood
  • Mistetone
  • Orobanche
  • Ganodema
State whether true or false:
The process of nitrogen-fixing is done by bacteria in the presence of oxygen.
  • True
  • False
Hepatitis-B is caused due to:-
  • Virus
  • Protozoa
  • Bacteria
  • Fungi

Vaccines contain dead or weakened microbes. 

  • True
  • False
One third of the global cases of Tuberculosis is in
  • Britain
  • Sweden
  • India
  • China
The organisms which cause diseases in plants and animals are called:
  • Pathogens
  • Vectors
  • Insects
  • Worms
An example of infectious disease is:
  • Cholera
  • Anaemia
  • Joint pain
  • Cancer
Blue-green algae are able to fix nitrogen from the _________________.
  • Water
  • Atmosphere
  • Soil
  • None of the above
Nitrogen is one of the essential constituents of all living organisms as part of 
  • Proteins
  • Chlorophyll
  • Nucleic acids
  • All of the above
State whether the given statement is True or False:
Due to the nitrogen cycle, the percentage of nitrogen in the atmosphere remains more or less constant.
  • True
  • False
The percentage of nitrogen in the atmosphere is_______.
  • 75%
  • 21%
  • 1.03%
  • 78%
Rhizobium bacteria live in the root nodules of 
  • Wheat
  • Palm trees
  • Legumes
  • None of the above

Nitrogen is absorbed by the plants in the form of____________.

    • Ammonium
    • Nitrites
    • Nitrates
    • All of the above
    Nitrogen fixation is the process of:
    • Conversion of atmospheric nitrogen into usable form
    • Conversion of ammonia into atmospheric nitrogen
    • Conversion of nitrate into atmospheric nitrogen
    • Conversion of atmospheric nitrogen into urea
    State whether the given statement is True or False:
    Nitrogen fixation in leguminous plants increases the soil fertility.
    • True
    • False
    The circulation of nitrogen between organisms and the atmosphere is called the _____________________.
    • Atmosphere
    • Nitrogen cycle
    • Oxygen cycle
    • Water cycle
    Which of the following unicellular organism can make people sick?
    • Bacteria
    • Earthworm
    • Frog
    • Rose
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