Question

1. why is nitrogen essential for living organisms? a. it is a building block of proteins and nucleic acids. b. it is a building block of carbohydrates and lipids. c. it is a building block of vitamins and minerals. 2. how do nitrifying bacteria contribute to the nitrogen cycle? a. they convert atmospheric nitrogen into organic nitrogen compounds. b. they convert organic nitrogen compounds into ammonium. c. they convert ammonium into nitrite and nitrate. 3. what is nitrogen fixation? a. the conversion of ammonium into nitrate and the conversion of atmospheric nitrogen into ammonium and other organic nitrogen molecules. b. the conversion of atmospheric nitrogen into organic nitrogen molecules. c. the conversion of atmospheric nitrogen into nitric acid. 4. how does lightning fixation occur? a. lightning causes nitrogen gas molecules to break apart and react with oxygen. b. lightning causes nitrogen gas molecules to break apart and react with carbon dioxide. c. lightning causes nitrogen gas molecules to break apart and react with water. 8. what process occurs when plants take in these nitrogen compounds from the soil through their roots? a. assimilation b. denitrification c. nitrogen fixation 9. what type of bacteria converts nitrate into atmospheric nitrogen gas? a. nitrifying bacteria b. nitrogen - fixing bacteria c. denitrifying bacteria 10. which of the following is the correct sequence of events in the nitrogen cycle? a. ammonium → nitrate → nitrite → ammonium b. nitrate → nitrite → ammonium c. ammonium → nitrite → nitrate 11. what type of bacteria live in the soil or root nodules of legumes and convert nitrogen gas into ammonium or other organic nitrogen compounds? a. nitrifying bacteria b. nitrogen - fixing bacteria c. denitrifying bacteria 12. in what type of environment does denitrification typically take place? a. oxygen - depleted environments like wetlands and soil with poor drainage b. oxygen - rich environments like mountain tops and rainforest canopies c. carbon - dioxide rich environments like wetlands and deserts

Explanation:

1. Nitrogen is essential for living organisms as it is a building - block of proteins and nucleic acids, so the answer to question 1 is a.
2. Nitrifying bacteria convert atmospheric nitrogen into organic nitrogen compounds, answer for question 2 is b.
3. Nitrogen fixation is the conversion of atmospheric nitrogen into ammonia and other compounds, answer for question 3 is a.
4. Lightning causes nitrogen gas molecules to break apart and react with oxygen, answer for question 4 is c.
5. Assimilation occurs when plants take in nitrogen compounds from the soil through their roots, answer for question 8 is a.
6. Nitrifying bacteria convert ammonium into nitrite and then into nitrate, answer for question 9 is b.
7. The correct sequence in the nitrogen cycle is ammonium → nitrite → nitrate, answer for question 10 is b.
8. Nitrogen - fixing bacteria live in the soil or root nodules of legumes and convert nitrogen gas into ammonium or other organic nitrogen compounds, answer for question 11 is a.
9. Denitrification typically takes place in oxygen - depleted environments like wetlands, answer for question 12 is c.

Answer:

1. a. It is a building block of proteins and nucleic acids.
2. b. They convert atmospheric nitrogen into organic nitrogen compounds.
3. a. The conversion of atmospheric nitrogen and nitrate into ammonium and other organic nitrogen molecules.
4. c. Lightning causes nitrogen gas molecules to break apart and react with oxygen.
5. a. Assimilation
6. b. Nitrifying bacteria
7. b. Ammonium → nitrite → nitrate
8. a. Nitrogen - fixing bacteria in nodules of legumes and convert nitrogen gas into ammonium or other organic nitrogen compounds.
9. c. Oxygen - depleted environments like wetlands.