Tag: bio-geo chemical cycles in nature

Quizzes (5) Questions (95)

Questions Related to bio-geo chemical cycles in nature

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

Which one is not a free living nitrogen fixer?

  1. Rhodospirillum

  2. Azotobacter

  3. Rhizobium

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

The organisms involved in nitrogen fixation are termed as nitrogen-fixing organisms. They convert free nitrogen (gaseous form dinitrogen, N2) into forms such as nitrates and nitrites that can be utilized by plants. These organisms could either be free-living or found in symbiotic, mutualistic, or commensalistic relationships with other plants etc. Rhizobium is found in a symbiotic relationship with plant roots. 

So, the correct answer is 'Rhizobium'.

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

Which of the following is free-living bacteria responsible for nitrogen fixation 

  1. Pseudomonas

  2. Rhodospirillum

  3. Azotobacter

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

Nitrogen-fixing microorganisms are recognized: free-living (non-symbiotic) bacteria, including the cyanobacteria. Anabaena and Nostoc and genera such as Azotobacter, Beijerinckia, and Clostridium and mutualistic bacteria such as Rhizobium, associated with leguminous plants.

So, the correct option is 'All of these'.

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

In the process of nitrification, ammonia is first oxidized to nitrite by

  1. Nitrosomonas and Nitrosococcus

  2. Nitrosomonas and Nitrobacter

  3. Pseudomonas and Nitrosococcus

  4. Pseudomonas and Thiobacillus
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

First step, ammonium ions are oxidised to nitrites. Nitrosomonas  are the  most important agents of oxidation of ammonia to nitrite in soil. Certain other bacteria are Nitrosococcus , Nitrosolobus ,etc.

Second step , oxidation of nitrite to nitrate takes place by Nitrobacter. 
So the correct option is "Nitrosomonas and Nitrococcus".

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

Which of the following is a symbiotic nitrogen fixer ?

  1. Azolla

  2. Glomus

  3. Azotobacter

  4. Frankia
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Symbiotic nitrogen fixation is part of a mutualistic relationship in which plants provide a niche and fixed carbon to bacteria in exchange for fixed nitrogen. Frankia is a nitrogen-fixing bacterium that lives in the soil and has a symbiotic relationship with many plants. Frankia is a genus of nitrogen-fixing, filamentous bacteria that live in symbiosis with actinorhizal plants, similar to the Rhizobium bacteria found in the root nodules of legumes in the family Fabaceae.

So, the correct answer is 'Frankia'.
Multiple choice zoology bio-geo chemical cycles in nature nitrogen cycle biogeochemical cycles - gaseous nutrient cycles

How many organisms In the list given below are $N _2$ fixer autotrophs?
Azotobacter, Chromobum, Azospirillum, Rhodospirillum, Rhizobium, Nitrobacter, Aulosira, Nostoc, Osallatona

  1. Three

  2. Four

  3. Five 

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

Nitrogen-fixing bacteria are capable of fixing atmospheric nitrogen to inorganic substances usable by plants. Example from the given list are Azetobactor, Azospirillum, Rhizobium, Nitrobactor and Nostoc.

So the correct answer is 'five'.

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 non - photosynthetic nitrogen-fixer ?

  1. $Rhizobium$

  2. $Azotobacter$

  3. $Azospirillum$

  4. $Nostoc$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Azotobacter is a free-living nitrogen-fixing bacterium, which is used as a biofertilizer in the cultivation of most crops. Azotobacter respires aerobically, receiving energy from redox reactions, using organic compounds as electron donors. Azotobacter can use a variety of carbohydrates, alcohols, and salts of organic acids as sources of carbon. 

Rhizobium fixes nitrogen by symbiotic association. Nostoc is photosynthetic. Azospirillum is anaerobic. 
So, the correct option is 'Azotobacter'.

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

All of the following statements concerning the actinomycetous filamentous soil bacterium Frankia are correct except that Frankia

  1. Can induce root nodules on many plant species

  2. Can fix nitrogen in the free-living state

  3. Like Rhizobium, it usually infects its host plant through root hair deformation and stimulates cell proliferation in the host's cortex

  4. Forms specialized vesicles in which the nitrogenase is protected from oxygen by a chemical barrier involving triterpene hopanoids
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Frankia is a bacterium which grows in a symbiotic association with the roots of non-leguminous plants.  It can fix atmospheric nitrogen. It cannot fix nitrogen in free-living state.

So, the correct option is 'Can fix nitrogen in free-living state'.

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

Bacteria involved in two-step conversion ammonia into nitrate are

  1. Azotobacter and Nitrosomonas

  2. Pseudomonas and Nitrobacter

  3. Azotobacter and Achromobacter

  4. Nitrosomonas and Nitrobacter
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Nitrification is a process of conversion of ammonium ions to nitrites and nitrites to nitrates. It is a two-step process. 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 'Nitrosomonas and Nitrobacter.'