Tag: nitrogen cycle

Questions Related to nitrogen cycle

Reaction carried out by $N _2$ fixing microbes include
$2NH _3 + 3O _2 \rightarrow 2NO _2^- + 2H^+ + 2H _2O$            (i)
$2NO _2^- + O _2 \rightarrow 2NO _3^-$                                       (ii)
Which of the following statements about these equations is not true?

zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

  1. Step (i) is carried out by Nitrosomonas or Nitrosococcus

  2. Step (ii) is carried out by Nitrobacter

  3. Both step (i) and (ii) can be called nitrification.

  4. Bacteria carrying out these steps are usually photoautotrophs.

Show answer
Correct Option: D
Explanation:
Phototrophic bacteria are a group of bacteria, whose energy for growth is derived from sunlight and their source of carbon comes from carbon dioxide or organic carbon.
So, the correct option is 'Bacteria carrying out these steps are usually photoautotrophs'.

A farmer adds Azotobacter culture to soil before sowing maize. Which mineral element will be replenished by doing so?

zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

  1. N

  2. P

  3. K

  4. S

Show answer
Correct Option: A
Explanation:
Azotobacter is a free living bacteria in the soil. It helps some cereal crops like maize (Zea mays) in nitrogen fixation. The farmer adds Azotobacter culture to the maize field for enhancing the nitrogen element in the soil by the process of biological nitrogen-fixation. 
Thus, the correct answer is 'N.'

Which of the following is a non-symbiotic nitrogen fixing prokaryote?

zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

  1. Azotobacter

  2. Clostridium

  3. Beijerinckia

  4. All of these

Show answer
Correct Option: D
Explanation:

Two kinds of nitrogen-fixing bacteria are recognized. The first kind, the free-living (non-symbiotic) bacteria, includes the cyanobacteria (or blue-green algae), Anabaena and Nostoc and genera such as Azotobacter, Beijerinckia, and Clostridium. 

Thus, the correct answers is 'All of these.'

Which of the following is a free living aerobic nitrogen fixing bacterium present in the soil?

zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

  1. Nitrosomonas

  2. Rhizobium

  3. Azotobacter

  4. Pseudomonas

Show answer
Correct Option: C
Explanation:

Azotobacter and Beijerinckia  are aerobic free living saprophytic nitrogen fixing bacteria, while Clostridium is anaerobic free living saprotrophic nitrogen fixing bacterium.

Mark the incorrect match.

zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

  1. Rhodospirillum-anaerobic nitrogen fixer

  2. Azotobacter- aerobic nitrogen fixer

  3. Bacillus vulgaris-denitrifying bacteria

  4. Rhizobium- $N _2$ fixation in alfalfa

Show answer
Correct Option: A

Which one of the following bacteria is not connected with nitrogen fixation?

zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

  1. Azotobacter

  2. Nitrosomonas

  3. Frankia

  4. Rhizobium

Show answer
Correct Option: B
Explanation:

Nitrogen fixation is referred to as conversion of atmospheric nitrogen into ammonia, whereas the Nitrosomonas is a genus of Gram-negative, chemoautotrophic bacteria. This organism oxidizes ammonia into nitrite as a metabolic process. 

 So, the correct option is 'Nitrosomonas'.

Which of the following is a flowering plant with nodules containing filamentous nitrogen-fixing microorganism?

zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

  1. Cicer arietinum

  2. Casuarina equisetifolia

  3. Crotalaria juncea

  4. Cycas revolute

Show answer
Correct Option: B
Explanation:
Answer :
i) All the casuarinas are nitrogen-fixing. 
ii) Casuarinas support an actinorhiza symbiont in their root nodules, as opposes to the rhizobium symbiont found in the root nodules of leguminous trees that fix N2. 

Therefore correct answer is option B.Casuarina equisetifolia.

Nitrifying bacteria convert the________________

zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

  1. Nitrates into nitrites

  2. Ammonium salts into nitrates

  3. Ammonium salts into amino acids

  4. All of the above

Show answer
Correct Option: B
Explanation:

Nitrifying bacteria are chemoautotrophic or chemolithotrophs depending on the genera (Nitrosomonas, Nitrosococcus, Nitrobacter, Nitrococcus) bacteria that grow by consuming inorganic nitrogen compounds. Many species of nitrifying bacteria have complex internal membrane systems that are the location for key enzymes in nitrification: ammonia monooxygenase, which oxidizes ammonia to hydroxylamine, and nitrite oxidoreductase, which oxidizes nitrite to nitrate. Nitrifying bacteria are a narrow species in the environment and are found in the lowest numbers, where considerable amounts of ammonia are present (areas with extensive protein decomposition, and sewage treatment plants). Nitrifying bacteria thrive in lakes and rivers streams with high inputs and outputs of sewage and wastewater and freshwater because of the low ammonia content.

An organism used as a biotertilizer for raising soyabean crops is ______________.

zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

  1. Azotobacter

  2. Azospirillum

  3. Rhizobium

  4. Nostoc

Show answer
Correct Option: C

Nitrifying bacteria _________________.

zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

  1. Oxidize.2riimonia to nitrates

  2. Convert free nitrogen to nitrogen compounds

  3. Convert proteins into ammonia

  4. Reduce nitrates to free nitrogen

Show answer
Correct Option: A