13.3 nutrient cycles

Question 1

how is NO3^- absorbed into plant roots?

Answer 1

by active transport

Question 2

ammonification

Answer 2

• NH4^+ compound in saprobionts -> NH4^+

- saprobionts and microorganisms

Question 3

nitrification

Answer 3

• NH4^+ -> NO2^- -> NO3^-

- nitrifying bacteria

Question 4

nitrogen fixation

Answer 4

• N2 -> NH4+
• fee- living nitrogen- fixing bacteria
• N2 -> NH4+ compounds in producers
• mutualistic nitrogen- fixing bacteria

Question 5

denitrification

Answer 5

• anaerobic
• denitrifying bacteria
• NO3^- -> N2

Question 6

phosphorus cycle

Answer 6

• phosphate is take up by plants
• phosphate ions pass into animals
• phosphate ions are excreted
• plants and animals die and bacteria and fungi break them down releasing phosphate ions
• phosphate ions remain on bones and shells
• transported into lakes where they form sedimentary rocks again

Question 7

roe of mycorrhizae

Answer 7

• helps increase the surface area of the plants root system so increase absorption of water and minerals

Question 8

what is mycorrhizae?

Answer 8

mutualistic symbiotic relationship between mycorrhizae fungi and roots of plants

Question 9

Describe how the action of microorganisms in the soil produces a source of nitrates for crop plants.
[5 marks]

Answer 9

1. Protein/amino acids/DNA into ammonium compounds / ammonia;
2. By saprobionts;
3. Ammonium/ammonia into nitrite;
4. Nitrite into nitrate;
5. By nitrifying bacteria/microorganisms;
6. Nitrogen to ammonia/ammonium;
7. By nitrogen-fixing bacteria/microorganisms in soil;

Question 10

In these forests, nitrogen in dead leaves is made available to growing plants by the action of bacteria. Describe the role of bacteria in making the nitrogen in dead leaves available to growing plants.
[5 marks]

Answer 10

1. Saprobionts/saprophytes;
2. Digest/break down proteins/DNA/nitrogen-containing substances;
3. Extracellular digestion/release of enzymes;
4. Ammonia/ammonium produced;
5. Ammonia converted to nitrite to nitrate/ammonia to nitrate;
6. Nitrifying (bacteria)/ nitrification;
7. Oxidation;