nutrient cycles

Question 1

describe the role of saprobionts in recycling chemical elements

Answer 1

1. feed on remains of dead plants/animals + break down organic molecules
2. secrete enzymes for extracellular digestion - absorb needed nutrients

Question 2

what do saprobionts break nitrogen containting organic molecules into and by what process

Answer 2

ammonium ions

ammonification

Question 3

desribe the role of mycorrihzae in recycling chemical elements

Answer 3

• symbiotic relationship between fungi and roots of plants
• fungi act as extension of plant roots (thin strands called hyphae) to increase sf area = increase uptake of water/nutrients
• mutualistic relationship - plant provides fungi with carbs

Question 4

four main stages of nitrogen cycle + type of microorganism involved

Answer 4

• ammonification -saprobionts
• nitrification - nitrifying bacteria
• nitrogen fixation - nitrogen fixing bacteria
• denitrifying bacteria - denitrifying bacteria

Question 5

desribe process of ammonifaction

Answer 5

• nitrogen containing compounds broken down
• converted to ammonia -> ammonium ions
• by saprobionts ( by secreting enzymes for extracellular digestion)

Question 6

describe process of nitrification

Answer 6

• ammonium ions in soil->nitrites->nitrates
• two stage oxidation reaction
• by nitrifying bacteria (need o2 to carry out conversions)``

Question 7

explain why farmers need to ensure soil is aerated

Answer 7

• nutrients can be absorbed by root hair cells by active transport
• application - increase 02, nitrifying bacteria increase , denitrying bacteria decrease = maximise nitrogen availability

Question 8

describe denitrification

Answer 8

• nitrates in soil ->nitrogen gas

- by denitrifying bacteria (anaerobically)

Question 9

why can flooding lead to less nitrate for crops

Answer 9

• low conc in soil
• more anaerobic denitrifying bacteria, less aerobic nitrogen fixing bacteria
• reduces availability of nitrogen compounds for plants

Question 10

desribe nitrogen fixation

Answer 10

• N2 gases (reduced) to nitrogen containing compounds

- nitrogen fixing bacteria

Question 11

how and where are nitrogen fixing bacteria found

Answer 11

• ‘free living’ in the soil

- ‘mutualistic’ -> live in nodules on roots of plants ie. legumes

Question 12

why is the nitrogen cycle important to all living organisms

Answer 12

• N2 gas unreactive + not easily converted to other compounds
• most plants can only uptake nitrogen as nitrates
• used by plants/ animals to make proteins/amino acids used for growth