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Important questions on Biogeochemical Cycles

The circulation of oxygen in various form through nature is called as

A

Respiration

B

Circulation

C

Oxygen cycle

D

All of the above

View Answer

Which bacteria is responsible to fix nitrogen in leguminous plants?

A

Azotobacter

B

Rhizobium

C

Clostridium

D

Saccharomycese

View Answer

Some bacteria maintain the soil fertility and others enhance it. The fertility of the soil is proportional to the nitrogen content. Nitrogen is an important ingredient in the structure and function of the living beings. Nitrogen-fixing bacteria like Azotobacter, Clostridium live free in the soil and fix atmospheric nitrogen. Rhizobium like bacteria live symbiotically with root systems of leguminous plants and fix from the atmospheric nitrogen. Therefore, the correct answer is option B.

Legume plants are important because they

A

Help in fixation

B

Not help in fixation

C

Increase soil fertility

D

All of the above

View Answer

Legume plants have root nodules, which harbor nitrogen fixing bacteria. These bacteria convert atmospheric nitrogen (which cannot be used by plants) into biologically useful form like ammonia. Hence, these plants increase soil fertility by increasing the nitrogen content in soil. 

.......... oxygen is present in the atmosphere.

A

78%

B

21%

C

3%

D

1%

View Answer

The bacterium nitrobacter converts

A

Nitrogen to nitrite

B

Ammonia to nitrite

C

Nitrite to nitrate

D

Nitrate to nitrite

View Answer

Nitrification is a two step process of converting ammonia into nitrites and nitrites into nitrates. Bacteria converting ammonia into nitrites includes Nitrosomonas. Bacteria converting nitrites to nitrates includes Nitrobacter.
Thus, the correct answer is 'Nitrite to nitrate.'

The microbial biofertilizers which can act both symbiotically and non-symbiotically to increases soil fertility are

A

Azotobacter

B

Rhizobium

C

Clostridium

D

`Nostoc and Anabaena

View Answer

Azotobacter can act both as symbiotically and non symbiotically to increase soil fertility. It Infuse the soil with antibiotic pesticides and inhabit the spread of soil borne diseases like pythium and phytophthora.

The atmosphere contains .......... % of oxygen.

A

21

B

13

C

75

D

17

View Answer

The atmosphere contains 21% oxygen. The level is maintained by respiration and photosynthesis. 
So, the correct answer is option A.

The wormicide character of _____ destroys worms in water.

A

Azotobacter

B

Azolla

C

Nostoc

D

None of these

View Answer

The wormicide character that kills worms in water are Azotobactor.
Azotobactors are one of the Nitrogen-fixing bacteria. Hence they are used as bio-fertilisers for many plants. 
The size of Azotobactor varies from 1-20 μm in length and 1-2 μm. 
Azotobactors can be generally found in alkaline soil and aquatic regions. So, the correct answer is A.

Who discovered oxygen?

A

Priestley

B

Winogradsky

C

Humphry

D

None of the above

View Answer

Identify the given biogeochemical cycle.

A

Mineral cycle

B

Nitrogen cycle

C

Water cycle

D

Oxygen cycle

View Answer

The assimilation of oxygen from the atmosphere to the biosphere is called as Oxygen cycle. 

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