Tag: nitrogen cycle

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Questions Related to nitrogen cycle

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

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?

  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.
Reveal answer Fill a bubble to check yourself
D Correct answer
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'.
Multiple choice zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

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

  1. N

  2. P

  3. K

  4. S
Reveal answer Fill a bubble to check yourself
A Correct answer
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.'

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

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

  1. Azotobacter

  2. Clostridium

  3. Beijerinckia

  4. All of these
Reveal answer Fill a bubble to check yourself
D Correct answer
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.'

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

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

  1. Nitrosomonas

  2. Rhizobium

  3. Azotobacter

  4. Pseudomonas
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

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

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

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

  1. Azotobacter

  2. Nitrosomonas

  3. Frankia

  4. Rhizobium
Reveal answer Fill a bubble to check yourself
B Correct answer
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'.

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

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

  1. Cicer arietinum

  2. Casuarina equisetifolia

  3. Crotalaria juncea

  4. Cycas revolute
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

Nitrifying bacteria convert the________________

  1. Nitrates into nitrites

  2. Ammonium salts into nitrates

  3. Ammonium salts into amino acids

  4. All of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

Nitrifying bacteria _________________.

  1. Oxidize.2riimonia to nitrates

  2. Convert free nitrogen to nitrogen compounds

  3. Convert proteins into ammonia

  4. Reduce nitrates to free nitrogen
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Nitrifying bacteria oxidize ammonia to nitrites and then to nitrates in a two-step process. Nitrosomonas converts ammonia to nitrite, and Nitrobacter converts nitrite to nitrate. This is part of the nitrogen cycle.