Mr P bio 4 nutrient cycles

Question 1

what is a carbon sink?

Answer 1

something that stores some carbon containing chemical compound for an indefinite period and removes co2 frm the atmosphere

Question 2

what are saprobionts and how do they digest?

Answer 2

e.g. bacteria and fungi and digest dead organisms through extracellular digestion releasing enzymes and breakng down organic molecules into inorganic molecules

Question 3

what fungi attaches to plant roots and what does it do?

Answer 3

mycorrhizae fungi made of long strands called hyphae (which increase SA) and this is a mutualistic relationship as they help plants in their uptake of inorganic ions and water and fungi gain organic compounds such as lgucose from plant

Question 4

what is the nitrogen cycle?

Answer 4

1)nitrogen fixing bacteria found in the soil and in some legumious plant roots turn Nitrogen gas in atmosphere into ammonium ions via hitrogen fixation
2) also sacrobionts in the soil can turn nitrogen compounds from dead animals or their excretion into ammonia through ammonification
3)nitrifying bacteria converts ammonia to nitrites and then nitrates via nitrification
4)nitrate used by plants too produce protein etc
5)plants are eaten and plants and animals die and animals extrete nitrogenous waste are broken down
6) also denitrification occurs via denitifying bacteria which turn nitrate to nitrogen gas as they need it for anaerobic respiration

Question 5

how can nitrogen in the air also be converted intro nitrates?

Answer 5

electrical fixation of N gad to nitrates ib soil due to lightning

Question 6

what is the phosphorous cycle? (soil)

Answer 6

1) most phosphates ions in rocks can be washed into soil due to erosion
2)phosphates taken intro plants via roots and assimilated by the plant
3)primary consumer feed on plants and phosphates taken in and made into new molecules then secondary consumer feeds on primary
4) organisms produce faeces containing phosphorous and are digested by sacrobiotic bacteria throguh extracellular digestion releasing phosphate ions back into the soil to be taken up by plants again

Question 7

phosphate cycle (sea)

Answer 7

1) phosphates dissolved from rock into water
2)algae can use phosphates for growth and passed along the aquatic food chain
3)phosphates returned to sea and soil via guano (excretion) of animals e.g. seagulls
4)also dead prganisms fall to bottom of sea and sediment builds on top and phosphates trapped in rocks

Question 8

what does nitrogen fixing bacteria convert?

Answer 8

nitrogen gas into ammonia

Question 9

what do saprobionts convert? (during the N cycle)

Answer 9

decompose proteins (from dead organisms/ waste) into ammonia

Question 10

describe nitrogen fixation

Answer 10

nitrogen gas is turned into nitrogen containing compounds carried out by bacteria. is a mutualistic relationship

Question 11

describe ammonification

Answer 11

nitrogen compounds (proteins/ amino acids) from dead organisms/ waste are converted into ammonia by sacrobionts

Question 12

describe nitrification

Answer 12

when ammonia ions in the soil are changed into nitrates- which can then be sued by plants.
1st, one type of nitrifying bacteria changes ammonia into nitrites
then another type converts nitrites into nitrates

Question 13

what does nitrifying bacteria convert?

Answer 13

ammonia into nitrites then nitrates

Question 14

describe denitrification

Answer 14

nitrates converted into nitrogen gas by denitrifying bacteria- use nitrates for respiration and produce N2.
happens under anaerobic conditions

Question 15

what does denitrifying bacteria convert?

Answer 15

nitrates into nitrogen gas

Question 16

how is an agricultural ecosystem different from natural ecosystem when organisms die?

Answer 16

N- they decompose
A- large amount os biomass are harvested or removes, which removes nutrients from the ecosystem so mineral ion conc decreases and so does productivity and crop yield

Question 17

what are the advantages of natural fertilisers?

Answer 17

A- cheap, improve soil structure + ability to retain water, reduces erosion, releases nutrients over a long period of time

Question 18

what is a natural fertiliser?

Answer 18

made from organic matter, including manure, composted vegetables, crops residues, sewage sludge and bone meal

Question 19

what are the disadvantages of natural fertilisers?

Answer 19

-extremely bulky and must be applied in large amounts
-difficult to spread, heavy machinery required
-weed seeds and fungal spores may be present in the manure-> introducing pests into the food chain
-sewage could contain heavy metals like lead, zinc + nickel

Question 20

what is an artificial fertiliser?

Answer 20

are inorganic- contain pure chemicals in the form of powders or pellets

Question 21

what are the advantages of artificial fertiliser?

Answer 21

-exact compositions of ions known -> can be matched to need of crops
-quick release of minerals
-concentrated so less applies- cheaper transport
-easy to apply
-soluble so mineral ions immediately available

Question 22

what are the disadvantages of artificial fertiliser?

Answer 22

-soluble so leads to leaching
-doesnt improve soil structure

Question 23

why are fertilisers needed?

Answer 23

minerals likely to be in short supply and are required for growth. phosphates and nitrates used to produce amino acids, ATP and nucleotides all needed for growth.
Potassium needed for AT and photosynthesis

Question 24

how do fertilisers increase productivity?

Answer 24

sufficient N, P and K ions provided so plants develop earlier, grow taller and have a greater leaf area which increase rate of photosynthesis and crop productivity

Question 25

what impact does increase in crop productivity have on the cost of food?

Answer 25

increases amount of crop produced so reduces food prices

Question 26

what can happen is excessive amount of soluble fertiliser are applied to an area?

Answer 26

excess NPK ions can leach into the waterways in a process called leaching.

Question 27

what is leaching?

Answer 27

when water soluble compounds in the soil are washed away

Question 28

why do artificial fertilisers cause leaching?

Answer 28

inorganic ions in artificial fertilisers are relatively soluble so excess minerals that arent immediately used are more likely to be leaches and especially more likely if applied before heavy rainfall

Question 29

why are natural fertilisers less likely to lead to leaching?

Answer 29

as the NPK are contained in organic molecules that must be broken down by microorganisms before they can be absorbed by plants

Question 30

how is eutrophication caused?

Answer 30

by excess nutrients entering a body of water which increases the nutrient conc in the water

Question 31

describe the process of eutrophication

Answer 31

1. nitrates from fertilisers leach into rivers/lakes 2growth of algae blocks sunlight 3. increasing comp for light 4. reduces phtoosynthesis 5.plants die increasing food availability for saprobionts 6.saprobionts aerobically respire 7. less O2 available for aerobic organisms like fish which die

Question 32

what happens after surface layer of algae prevents light passing through? (eutrophication)

Answer 32

1. light now LM for growth of plants and algae at lower depths so die 2lack of dead plants and algae no longer LF for growth of sacrobiotic bacteria so they grow 3. sacrophytes require O2 for respiration so increase in O2 demand 4.O2 levels decrease and further nitrates released form decaying organisms 5.O2 now limiting factor for the populations of aerobic organisms like fish which die 6. less aerobic organisms so pop of anaerobic organisms rise due to lack of comp 7. anaerobic organisms further decompose dead material releasing more nitrates and some toxic wattes making water putrid

Question 33

how do fertilisers affect biodiversity?

Answer 33

reduce biodiversity. N rich soil favours growth of grasses, nettles and other rapidly growing species, which outcompete other causing them to die.