Question

number correct 16 number incorrect 0 which of the following statements is true about the nitrogen cycle? i. bacteria are very important in the nitrogen cycle. without these bacteria, it would be very difficult for other life forms to exist. ii. nitrogen fixation occurs when bacteria take nitrogen gas out of the air and make it into ammonia. this can then be converted into nitrates that plants can use. iii. decomposition is not very important in the nitrogen cycle. iv. nitrogen is needed to make dna, proteins, atp and other important molecules for life. the nitrogen cycle makes nitrogen available to living things. a. i, ii and iv only. b. i and iv only c. i, ii, iii, and iv d. ii only click to choose your answer below: a b c d

Explanation:

• Statement I: Bacteria play crucial roles in nitrogen - fixation (e.g., Rhizobium), nitrification (converting ammonia to nitrates), and denitrification. Without them, the cycling of nitrogen would be severely disrupted, making it hard for other organisms (which need nitrogen - containing compounds) to exist.
• Statement II: Nitrogen - fixing bacteria (e.g., free - living Azotobacter or symbiotic Rhizobium) take \(N_2\) from the air and convert it to ammonia (\(NH_3\)). Ammonia can then be converted to nitrates (\(NO_3^-\)) through nitrification, which plants can absorb.
• Statement III: Decomposition is important. When organisms die, decomposers break down their organic matter. This releases nitrogen - containing compounds (like ammonia) back into the environment, which can then re - enter the nitrogen cycle. So, this statement is false.
• Statement IV: Nitrogen is a component of DNA (in nucleotides), proteins (in amino acids), and ATP (adenosine tri - phosphate). The nitrogen cycle ensures that nitrogen is available in forms (like nitrates for plants, and then through the food chain for animals) that living organisms can use.

Answer:

A. I, II and IV only.