Chapter 2, Problem 31A

Summary Introduction

Introduction :

Nitrogen is an important element and is an important constituent of proteins and nucleic acids in the organisms. The nitrogen is found in atmosphere in large concentration and it is found in plants, animals and in bacteria. The plants and animals cannot use atmospheric nitrogen directly. Nitrogen goes to the plants and animals through biological nitrogen fixation.

Answer to Problem 31A

Correct answer :

The correct answer is option (B) atmosphere.

Explanation of Solution

Explanation/justification for the correct answer :

Option (B) atmosphere. The largest concentration of nitrogen is found in the atmosphere. Approximately 78% of the air is the nitrogen but plants and animals cannot use atmospheric nitrogen directly but gets nitrogen through nitrogen fixation.

Thus, the correct answer is an option (B).

The explanation for the incorrect answer :

Option (A) Animals. Animals get nitrogen from the plants through food. They have limited nitrogen. Thus, this is an incorrect option.

Option (C) bacteria. Some bacteria such as Rhizobium fixes atmospheric nitrogen. Thus, this is an incorrect answer.

Option (D) plants. Plants get nitrogen from the soil which is fixed and converted into usable form by bacteria. Thus, this is an incorrect answer.