Tag: bio-geo chemical cycles in nature

Questions Related to bio-geo chemical cycles in nature

The bacteria present in root nodules of leguminous plants that fix the atmospheric nitrogen is

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

  1. Rhizobium

  2. Blue-green algae

  3. Nitrifying bacteria

  4. Paramecium

Show answer
Correct Option: A
Explanation:

Rhizobium is a bacterium found in the root nodules of leguminous plants. It induces the formation of special structures called nodules inside which it fixes atmospheric nitrogen. It does this with the help of nitrogenase enzyme that converts of nitrogen to ammonium that is an important factor required for plant growth. In turn, the bacterium receives shelter from the plant. Thus the correct answer is option A.

Oxidation of nitrite into nitrate is done by

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

  1. E. coli

  2. Nitrobacter

  3. Pseudomonas

  4. All of the above

Show answer
Correct Option: B
Explanation:

The second step (oxidation of nitrite into nitrate) is done mainly by bacteria of the genus Nitrosomonas and Nitrobacter.

Oxidation of Ammonia into nitrite is performed by


(a) Nitrosomonas (b) Nitrosococcus (c) Nitrobacter (d) Nitrospira

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

  1. a, b

  2. b, c

  3. c, d

  4. a, d

Show answer
Correct Option: A
Explanation:

Oxidation of Ammonia to nitrite is performed by two groups of bacteria. Nitrosomonas and Nitrosocossus are examples of bacterias which perform the oxidation of ammonia to nitrite.

Anaerobic bacteria are poisoned by which element ?

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

  1. Oxygen

  2. Nitrogen

  3. Carbon dioxide

  4. Carbon

Show answer
Correct Option: A
Explanation:

Anaerobic bacteria do not need oxygen. This is because they don't  use oxygen in any of their processes. Thus bacteria are poisoned by oxygen.

Nitrifying bacteria convert the

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

  1. Nitrates into nitrites

  2. Nitrites into nitrates

  3. Ammonium salts into nitrates

  4. Ammonium salts into amino acids

Show answer
Correct Option: C
Explanation:

Nitrification is a process of conversion of ammonium salts to nitrites and nitrites to nitrates. The bacteria that carry out this process are called as nitrifying bacteria. Nitrosomonas, Nitrosospira, Nitrosococcus convert ammonia into nitrites. Nitrobacter, Nitrospina, Nitrococcus convert nitrites into nitrates.

Thus, the correct answer is 'Ammonium salts into nitrates.'

In excess, $C{O} _{2}$

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

  1. Accelerates growth

  2. Does not influence growth

  3. Inhibits growth

  4. Slows down growth

Show answer
Correct Option: C
Explanation:

Atmospheric carbon dioxide is used by plants to produced food. Due to industrialization, large amount of carbon dioxide is released in the atmosphere. This CO$ _2$ provides nutrient source to certain plants. However, excess amount of CO$ _2$ inhibits growth in plants. It inhibits nitrate assimilation in certain plants. It basically inhibits absorption of nitrogen.

Thus, the correct answer is option C.

Nitrosomonas and Nitrobacter convert

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

  1. Carbon dioxide to carbohydrates

  2. Ammonium ion into nitrate

  3. Nitrate ion into nitrogen molecule

  4. Nitrogen into nitrate

Show answer
Correct Option: B
Explanation:

Nitrification is a process of conversion of ammonium ions to nitrites and nitrites to nitrates. The bacteria that carry out this process are called as nitrifying bacteria. Nitrosomonas, Nitrosospira, Nitrosococcus convert ammonia into nitrites. Nitrobacter, Nitrospina, Nitrococcus convert nitrites into nitrates.

Thus, the correct answer is 'Ammonium ion into nitrate.' 

The common nitrogen fixer organism in paddy fields is

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

  1. Azospirillum

  2. Oscillatoria

  3. Frankia

  4. Rhizobium

Show answer
Correct Option: A
Explanation:

Atmospheric nitrogen is not available to plants. There are certain nitrogen fixing bacteria which converts atmospheric nitrogen into ammonium compounds and make it available to the plants. Examples include Azotobacter, Frankia, Rhizobium, Azospirillum. Out of these, Azospirillum is widely used as nitrogen fixer organism in paddy fields. It is used as biofertilizer in rice fields. It promotes the plant growth.

Thus, the correct answer is 'Azospirillum.'

Nitrite is changed to nitrate by

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

  1. Nitrobacter

  2. Nitrosomonas

  3. Clostridium

  4. Pseudomonas

Show answer
Correct Option: A
Explanation:

There are two steps in nitrification process by which ammonia is converted into nitrite and nitrite into nitrate. The bacteria that convert ammonia to nitrites include Nitrosomonas, Nitrosospira and the bacteria that convert nitrites to nitrates include Nitrobacter, Nitrospina. 

Thus, the correct answer is 'Nitrobacter.'

Carefully read the following reactions carried out by nitrifying bacteria. Identify the statement about these equations which is not true.
2NH$ _3$+3O$ _2$ $\rightarrow$ 2NO$^- _2$ +2H$^+$ +2H$ _2O$ ---- (I)
2NO$^- _2$+O$ _2$ $\rightarrow$ 2NO$^- _3$ ---- (II)

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 the steps I and II can be called nitrification

  4. Both the steps occur only in photoautotrophs

Show answer
Correct Option: D
Explanation:
I) In the first step, ammonia is oxidised to nitrites by the action of nitrosomonas and nitrococcus bacteria.
II) In the second step, nitrate is further oxidised to nitrate with the help of nitrobacter and nitrocystis.
Both the reaction is involved in the process of nitrification. These nitrifying bacteria involved are called chemoautotrophs.
So the correct answer is 'Both the steps occur only in photoautotrophs'.