Nutrient cycles

Question 1

what is the similar pattern all nutrient cycles follow

Answer 1

1- nutrient is taken up by producers (plants) as simple, inorganic molecules
2- producer incorporates the nutrient into complex organic molecules
3-when producer is eaten, nutrient passes into the consumer
4-it passes along the food chain when these animals are eaten by consumers
5- when producers/consumers die, their complex molecules are broken down by saprobionts that release the nutrient in its original simple form.

Question 2

role of saprobionts

Answer 2

very important
without them, nutrients would be locked as complex molecules that cant be taken up by the plants
the cycle would not be complete

Question 3

what form of nitrogen do plants take up most of the nitrogen they require
how are they absorbed

Answer 3

nitrate ions NO3-

absorbed by active transport in the roots

Question 4

features of nitrate ions

Answer 4

incredibly soluble- easily leached through the soil

Question 5

define ammonification

Answer 5

production of ammonia from organic nitrogen containing compounds.

Question 6

how does ammonification occur?

Answer 6

saprobionts (mainly fungi and bacteria) feed on faeces and dead organic matter, releasing ammonia, which then forms ammonium ions in the soil- nitrogen is returned to the non living component of the ecosystem

Question 7

how does ammonification occur? (arrow explanation)

Answer 7

organic nitrogen containing compounds-> ammonia (by saprobionts)-> ammonium ions

Question 8

define nitrification

Answer 8

the conversion of ammonium ions to nitrate ions

Question 9

how is nitrification carried out?

Answer 9

carried out by free living soil microorganism called nitrifying bacteria:
1- oxidation of ammonium ions to nitrite ions (NO2-)
2- oxidation of nitrite ions to nitrate ions (NO3-)

Question 10

is nitrification an oxidation or reduction reaction

Answer 10

oxidation therefore releases energy

Question 11

why does the soil need to be oxygen rich

Answer 11

in order for nitrification to occur as it is an oxidation reaction

Question 12

how can you keep soil oxygen rich

Answer 12

ploughing- ensures there are air spaces in soil which contain oxygen
draining- creates more space for oxygen
mineral ions are very soluble so if there was lots of water leaching would occur -> soluble nutrients moved away with water

Question 13

nitrification in arrows

Answer 13

ammonium ions -> nitrite (NO2-) -> nitrate ions (NO3-)

Question 14

nitrogen fixation

Answer 14

nitrogen gas is converted into nitrogen containing compounds.

Question 15

what are the 2 types of microorganisms that carry out nitrogen fixation

Answer 15

1- free living nitrogen fixing bacteria

2- mutualistic nitrogen fixing bacteria

Question 16

how do free living nitrogen fixing bacteria carry out nitrogen fixation

Answer 16

they reduce gaseous nitrogen to ammonia which is used to make AAs. nitrogen rich compounds released when they die and decay.

Question 17

how do mutualistic nitrogen fixing bacteria carry out nitrogen fixation

Answer 17

live in nodules on the roots of plants. obtain carbs from the plant and the plant acquires AA from the bacteria

Question 18

denitrification

Answer 18

when soil is waterlogged, oxygen conc is low so the types of microorganisms present changes.
fewer aerobic nitrifying and nitrogen fixing bacteria are found- more anaerobic denitrifying bacteria are present.
they convert soil nitrates into gaseous nitrogen
reducing amount of nitrogen containing compounds for plants

Question 19

importance of airing soil

Answer 19

denitrification occurs
when soil is waterlogged, oxygen conc is low so the types of microorganisms present changes.
fewer aerobic nitrifying and nitrogen fixing bacteria are found- more anaerobic denitrifying bacteria are present.
they convert soil nitrates into gaseous nitrogen
reducing amount of nitrogen containing compounds for plants

Question 20

is there a gas stage in phosphorus cycle?

Answer 20

no as phosphorus is only found in mineral form and not in the atmosphere

Question 21

the phosphorus cycle

Answer 21

phosphorus exists mainly as (PO43-) in the form of sedimentary rock deposits.
weathering and erosion of these rocks helps phosphate ions to dissolve and so able to be absorbed by plants and transferred to their biomass
animals eat plant and therefore the phosphate ions
plants/animals die so decomposers release their phosphate ions into soil
some remain in animal as bone (cant be digested)
some phosphate ions transported into streams and rivers into lakes and oceans where they form sedimentary rocks- cycle complete

Question 22

what are Mycorrhizae

Answer 22

associations between certain types of fungi and the roots of plants

Question 23

how does mycorrhizae play an important part in the nutrient cycles

Answer 23

fungi acts as extensions to roots- increases SA- increases absorption of water and minerals
improves the uptake of scarce ions such as phosphate ions
mutualistic relationship- plant benefits from improved water and inorganic ion uptake, fungus receives organic compounds such as sugars and AA from the plant

Question 24

Summary of nitrogen cycle

Answer 24

Ammonification- (nitrogen containing compounds to ammonia to ammonium)
Nitrification (ammonium to nitrite to nitrate)
Denitrification- (nitrate ions to gaseous nitrogen)
Nitrogen fixation-( gaseous nitrogen to nitrogen containing compounds by free living nitrogen fixing bacteria or mutualistic nitrogen fixing bacteria)