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Microbes in Human Welfare · Question 63

AIPMT 2007MCQMedium📈 Topic in 12% papers+4−1
1

Which one of the following statements is correct?

  1. Cyanobacteria such as Anabaena and Nostoc are important mobilizers of phosphates and potassium for plant nutrition in soil
  2. Both Azotobacter and Rhizobium fix atmospheric nitrogen in root nodules of plants
  3. At present it is not possible to grow maize without chemical fertilizers
  4. Extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies

Answer

(4) Extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies

Solution

Option (1): As per NCERT, cyanobacteria such as Anabaena, Nostoc and Oscillatoria are autotrophic microbes that fix atmospheric nitrogen; phosphorus is absorbed from soil with the help of fungi (mycorrhiza). ⇒ Incorrect.

Option (2): Rhizobium fixes nitrogen in root nodules of legumes, but Azotobacter is free-living in soil and forms no nodules. ⇒ Incorrect.

Option (3): Maize can be grown using biofertilisers and manures (e.g., with Azospirillum / Azotobacter), so chemical fertilisers are not indispensable. ⇒ Incorrect.

Option (4): Nitrates and phosphates from excess fertilisers are washed into nearby lakes and ponds, act as plant nutrients and cause algal blooms, i.e., eutrophication. ⇒ Correct.

Answer: (4)

Out of syllabusAIPMT 2007

Keep practising — Microbes in Human Welfare

2

Curing of tea leaves is brought about by the activity of

  1. fungi
  2. bacteria
  3. mycorrhiza
  4. viruses
AIPMT 2006
3

For retting of jute the fermenting microbe used is

  1. methanophilic bacteria
  2. butyric acid bacteria
  3. Helicobacter pylori
  4. Streptococcus lactis.
AIPMT 2005
4

A free living nitrogen-fixing cyanobacterium which can also form symbiotic association with the water fern Azolla is

  1. Tolypothrix
  2. Chlorella
  3. Nostoc
  4. Anabaena
AIPMT 2004
5

Dough kept overnight in warm weather becomes soft and spongy because of :-

  1. Cohesion
  2. Absorption of carbon dioxide from atmosphere
  3. Osmosis
  4. Fermentation
AIPMT 2004
6

Which one of the following pairs is not correctly matched ?

  1. Spirulina – Single cell protein
  2. Streptomyces – Antibiotic
  3. Rhizobium – Biofertilizer
  4. Serratia – Drug addiction
AIPMT 2004
7

A major component of gobar gas is

  1. ethane
  2. methane
  3. butane
  4. ammonia
AIPMT 2004
8

Which of the following plants are used as green manure in crop fields and in sandy soils ?

  1. Calotropis procera and Phyllanthus niruri
  2. Dichanthium annulatum and Azolla nilotica
  3. Saccharum munja and Lantana camara
  4. Crotalaria juncea and Alhagi camelorum
AIPMT 2003
9

During anaerobic digestion of organic waste, such as in producing biogas, which one of the following is left undegraded :-

  1. Lignin
  2. Cellulose
  3. Hemi-cellulose
  4. Lipids
AIPMT 2003
10

Which bacteria is utilized in Gobar gas plant ?

  1. Nitrifying bacteria
  2. Methanogens
  3. Ammonifying bacteria
  4. Denitrifying bacteria
AIPMT 2002
11

During the formation of bread it becomes porous due to release of CO2 by the action of : -

  1. Protozoans
  2. Bacteria
  3. Yeast
  4. Virus
AIPMT 2002

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