CIE Biology Paper-4: Specimen Questions 28 - 31 of 120

Passage

The transformations that nitrogen undergoes as it moves between the atmosphere, the land and living things make up the nitrogen cycle.

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Diagram shows a part of nitrogen cycle. Name the step of nitrogen cycle and label the part A and B.

Diagram shows a part of nitrogen cycle

Diagram shows a part of nitrogen cycle

Diagram shows a part of nitrogen cycle name the label part A and B

Explanation

This is the first step of nitrogen cycle called as nitrogen fixation. In which atmospheric nitrogen is converted into ammonia.

Part A –Nitrogen fixation by lightning

Part B-Nitrogen fixation by bacteria in root nodules of leguminous plants

Question number: 29 (2 of 3 Based on Passage) Show Passage

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Write the name of some microorganism involve in nitrogen cycle

Explanation

In nitrification- Nitrosomoas and Nitrobacter-

In Denitrification-Pseudomonas spp. , Achromobacter spp. , Paracoccus spp. , Moraxella spp. , Bacillus spp. , Alcaligenes spp. , and Gluconobacter spp

Nitrogen fixation-Rhizobium

Question number: 30 (3 of 3 Based on Passage) Show Passage

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What is the role of denitrifying bacteria in nitrogen cycle?

Explanation

Denitrifying bacteria present in the soil break down nitrates and return nitrogen gas into the air.

Question number: 31

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The pH of rainwater is little below than 7. Why?

Explanation

Rainwater is usually acidic in nature because carbon di oxide dissolved in it to form carbonic acid. Sometimes SO2 and NO2 are also added in atmosphere to make rainwater more acidic.

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