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Bio-geo chemical cycles in nature - class-IX

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The wormicide character of _____ destroys worms in water.

  1. Azotobacter

  2. Azolla

  3. Nostoc

  4. None of these


Correct Option: A
Explanation:
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.

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

  1. Respiration

  2. Circulation

  3. Oxygen cycle

  4. All of the above


Correct Option: C

Which bacteria is responsible to fix nitrogen in leguminous plants?

  1. Azotobacter

  2. Rhizobium

  3. Clostridium

  4. Saccharomycese


Correct Option: B
Explanation:

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.

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

  1. Azotobacter

  2. Rhizobium

  3. Clostridium

  4. `Nostoc and Anabaena


Correct Option: A
Explanation:

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.

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

  1. 78%

  2. 21%

  3. 3%

  4. 1%


Correct Option: B

Free living nitrogen fixing biofertilizer is

  1. Glomus

  2. Rhizobium

  3. Azotobacter

  4. Pseudomonas


Correct Option: C
Explanation:

Azotobacter is a heterotrophic free living nitrogen fixing bacteria present in alkaline and neutral soils.

Some of the nutrient cycles are labelled as below. Sulphur
cycle (A), phosphorus cycle (B), carbon cycle (C) and
nitrogen cycle (D)
Of these, the sedimentary cycle is represented by

  1. (A) only

  2. (B) only

  3. (C) only

  4. (A) and (B) only

  5. (C) and (D) only


Correct Option: D

Who discovered oxygen?

  1. Priestley

  2. Winogradsky

  3. Humphry

  4. None of the above


Correct Option: A

Burning of fossil fuels affects

  1. Nitrogen cycle

  2. Carbon cycle

  3. Phosphorus cycle

  4. Water cycle


Correct Option: B

The bacterium nitrobacter converts

  1. Nitrogen to nitrite

  2. Ammonia to nitrite

  3. Nitrite to nitrate

  4. Nitrate to nitrite


Correct Option: C
Explanation:

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.'

Nitrogen fixing bacteria- anabaena - are found in the plant ______

  1. Azolla leaves

  2. Cycas corolloid roots
  3. Anthoceros body

  4. All of these


Correct Option: D
Explanation:
Anabaena are the one type of cyanobacteria, present in the leaves of Azolla, Corolloid roots of Cycas, Anthoceros body. They perform symbiotic Nitrogen fixation.
So the correct option is 'All of these'.

The biological process by which carbon is returned to its reservoir is

  1. photosynthesis

  2. denitrification

  3. carbon fixation

  4. cellular respiration


Correct Option: D
Explanation:
A. Photosynthesis is the process in which plants prepare their own food using carbon dioxide and water which are converted into glucose in the presence of sunlight along with the release of oxygen.
B. Denitrification is a process of reduction of nitrate into molecular nitrogen by denitrifying bacteria.
C. Carbon fixation is the reduction and incorporation of inorganic carbon into organic compounds.
D. Cellular respiration is a metabolic reaction in which energy is released from the breakdown of complex substances. Oxygen is used in respiration and carbon dioxide is released. Hence, carbon is returned to its reservoir through cellular respiration.
So, the correct answer is 'cellular respiration'.

Which one of the following is a wrong statement ? 

  1. Phosphorus is a constituent of cell membranes, certain nucleic acids and all proteins

  2. Nitrosomonas and Nitrobacter are chemoautotrophs

  3. Anabaena and Nostoc are capable of fixing nitrogen in free living state

  4. Root nodule forming nitrogen fixers live as aerobes under free living conditions


Correct Option: A
Explanation:
A. Phosphorus is constituent of cell membranes in the form of phospholipids and also present in nucleic acids as phosphate in the sugar-phosphate backbone.
B. Nitrosomonas and Nitrobacter are nitrifying bacteria. These bacteria derive energy by oxidizing inorganic nitrogenous compounds. Hence, they are called chemoautotrophs.
C. Anabaena and Nostoc are cyanobacteria (also known as blue-green algae). They are free-living bacteria and can fix nitrogen because they have specialized cells called heterocysts with the help of which they can fix atmospheric nitrogen.
D. Root nodule forming nitrogen-fixing microbes live freely in the soil as aerobes. They form a symbiotic association with the roots of plants when some chemicals or factors are released by the plants. For example, Rhizobium.
Hence, statement A is incorrect.
So, the correct answer is 'Phosphorus is a constituent of cell membranes, certain nucleic acids, and all proteins'.

The bacteria ______ supply natural manure to paddy fields.

  1. Azolla

  2. Anabaena

  3. Azotobacter

  4. Nostoc


Correct Option: A
Explanation:
The bacteria Azolla supplies natural manure to the paddy fields. Azolla is a gliding pteridophyte, which contains as endosymbiont the nitrogen-settling cyanobacterium Anabaena azollae (Nostocaceae family). 
Generally developed in the Asian districts, Azolla is either consolidated into the dirt before rice transplanting or developed as a double product alongside rice. 
So, the correct answer is A.

True or False:
Burning of fossil fuels liberate oxygen.

  1. True

  2. False


Correct Option: A

Which gas is likely to be reduced in the atmosphere by deforestation?

  1. Carbon dioxide

  2. Nitrogen

  3. Oxygen

  4. Sulphur dioxide


Correct Option: C

The ozone at ground level is primarily from__________ precursors

  1. Fossil fuel

  2. $CFC _{S}$

  3. Oxygen

  4. Methane


Correct Option: A

Phosphorous, is needed for the

  1. Growth

  2. Decomposition

  3. Photosynthesis

  4. Eutrophication


Correct Option: C

Which chemical was used as a foam blowing agents?

  1. Cl

  2. CFCs

  3. PAN

  4. Feron 11


Correct Option: B

What is concentration of $O _{2}$ in atmosphere?

  1. 12%

  2. 20.90%

  3. 21%

  4. 22%


Correct Option: B

What does 'Aluminum' irritate?

  1. Brook trout's gills

  2. Shark's gills

  3. Zooplankton's gills

  4. Phytoplankton's gills


Correct Option: A

In ocean, carbon is usually in form of:

  1. Bicarbonates ions

  2. Carbon dioxide

  3. Calcium

  4. Phosphorous


Correct Option: A

Emission of $CO$ and $NO _{2}$ are responsible for higher concentration of $O _{3}$ in

  1. Stratosphere

  2. Troposphere

  3. Thermosphere

  4. Biosphere


Correct Option: B

What is natural sources of CO?

  1. solid waste disposal

  2. Volcanic eruption and forest fire

  3. Motor vehicles

  4. Fuel combustion


Correct Option: B

One molecule of CFCs contain 15000 molecules of

  1. $CO _{2}$

  2. $CO$

  3. HCFCs

  4. CH4


Correct Option: A

Proportion of CO consumption consists of basic components:

  1. The leaf boundary layer

  2. The stomata

  3. Radiation exchange

  4. All of Above


Correct Option: D

Carbon dioxide constitutes about 0.03% of the atmosphere

  1. By volume

  2. By weight

  3. By mass

  4. None of these


Correct Option: A
Explanation:

The air in our atmosphere is composed of molecules of different gases. The most common gases nitrogen  (78%), oxygen (about 21%), argon (almost 1%) and carbon dioxide (0.03%). Other molecules are present in  the atmosphere as well, but in very small quantities. Composition of air is measured in percent by volume,  at sea level at 15C and 101325 Pa.

Phtotochemical phase does not includes ________________.

  1. Fixation of ${CO} _{2}$

  2. Release of ${O} _{2}$

  3. Photolysis of water

  4. Formation of ATP and NADPH


Correct Option: A
Explanation:

Photochemical phase includes photolysis of water and production of assimilatory power (ATP and NADPH). It liberates O2  during photolysis of water. 

The photochemical phase do not include fixation of CO2.

Chemical reactions triggered by ___________ transforms the organic material into hydrocarbons.

  1. solar energy

  2. hydroelectric

  3. elevated temperatures

  4. decomposition


Correct Option: C
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