energy transfers

Question 1

energy lost between trophic levels

Answer 1

-some parts aren’t eaten (e.g. bones and roots)
-some parts are eaten but not absorbed (lost in faeces)
-some of the biomass is eaten and absorbed (lost in urine)
-some of the biomass is broken down is respiration (temperature regulation and movement)

Question 2

reasons why energy may not be converted into biomass

Answer 2

-some energy is reflected back into space by the atmosphere
-not all wave lengths can be absorbed
-some light doesn’t hit the chlorophyll molecule
-other limiting factors may be involved

Question 3

biomass

Answer 3

-the dry mass of carbon in an organism in a particular area

Question 4

GPP

Answer 4

-the rate at which plants convert light energy into biomass during photosynthesis

Question 5

NPP

Answer 5

-the energy stored in biomass
-it takes into account the loss in respiration

Question 6

calculating NPP

Answer 6

N = I - ( F + R )
N= NPP
I= chemical energy store in ingested food
F= chemical energy lost in faeces and urine
R= respiratory loss

Question 7

calculating energy loss

Answer 7

energy available after transfer / energy available before transfer x100

Question 8

nitrification

Answer 8

NH4+ to NO3-
-nitrifying bacteria is involved
-its aerobic
-it occurs in the air spaces in the soil

Question 9

denitrification

Answer 9

NO3- to N2
-denitrifying bacteria is used
-its anaerobic
-it occurs when the soil gets filled with water

Question 10

ammonifcation

Answer 10

N2 to NH4+ (organic nitrogen to ammonia)
-it takes place in saprobionts (specifically in the root nodules)
-it occurs in faeces and decaying matter

Question 11

nitrogen fixing

Answer 11

N2 to NH4+ (nitrogen gas to nitrogen containing compounds)
-it occurs in root nodules of plants (leguminous plants)
-nitrogen fixing bacteria is used

Question 12

advantages of natural fertilisers

Answer 12

-they increase plant growth
-they improve yield
-they’re cheaper than artificial fertilisers

Question 13

disadvantages of natural fertilisers

Answer 13

-they take time to make
-they are not all of the same quality
-large amounts are needed

Question 14

advantages of artificial fertilisers

Answer 14

-they increase plant growth
-they improve yield
-only small amounts are needed
-they’re easy to use

Question 15

disadvantages of artificial fertilisers

Answer 15

-they are easily washed away
-they have a negative effect on microorganisms
-they can effect soil structure

Question 16

eutrophication

Answer 16

-excess nitrates run off into bodies of water
-this causes excess growth of alage on the surface of the water
-reduced light so aquatic plants die
-sapribionts respire aerobically while decomposing dead matter
-less oxygen for fish and other organisms so they die

Question 17

ploughing optimising the nitrogen cycle

Answer 17

-the process of breaking and loosening the soil
-this increases air flow and hence there is more oxygen for aerobic respiration of nitrifying bacteria (which convert ammonia into nitrates)
-this increases yield as there are more nitrates available in the soil for the plants to grow

Question 18

legumes optimising the nitrogen cycle

Answer 18

-they introduce nitrogen into the cycle, specifically ammonia and nitrates
-they increase soil fertility so the yield is increased

Question 19

crop rotation optimising the nitrogen cycle

Answer 19

-it reduces anaerobic conditions so that less denitrification occurs
-this means that more oxidation occurs
-this increases the yield

Question 20

nitrogen cycle

Answer 20

-nitrogen gas in the air is converted to ammonia in the soil by nitrogen fixing bacteria
-some nitrogen fixing bacteria in leguminous plant root nodules have a mutualistic relationship with plants and convert nitrogen gas into ammonia and nitrates
-nitrates in the soil are absorbed by plant roosts and converted into nitrogen containing compounds e.g. amino acids and DNA
-nitrogen containing compounds may be absorbed when eaten by consumers
-proteins from waste and dead material are broken down/ hydrolysed to ammonia in soil by enzymes released by saprobionts during ammonification
-ammonia in the soil is oxidised to nitrites, then nitrates by nitrifying bacteria in aerobic conditions
-if the soil is waterlogged, the lack of oxygen leads to denitrification where the nitrates are converted back to nitrogen gas by denitrifying bacteria

Question 21

phosphorus cycle

Answer 21

-plants absorb phosphorus from the soil
-consumers eat the plants and absorb the phosphorus
-dead and waste material is decomposed, releasing phosphorus into the soil
-runoff from farm fertiliser means excess phosphorus enters bodies of water
-weathering releases phosphorus from the rock into the water and soil
-leeching of phosphorus from the soil/ weathered rock causes phosphorus to enter the water