1. (a) (i) (Few species adapted to) hostile/harsh environment/colonising bare/
volcanic/fresh rock/little/no soil/water/humus; 1
(ii) Colonisers erode rock/release minerals;
add (more) humus/increase nitrate content/organic material;
when colonisers die/decompose; max. 2
(b) More/less competition; 1
[4]
2. (a) Mark for principle of placing quadrats at random;
marks for detail -
(method of) marking area out with grid/using tapes;
acceptable method of generating random numbers; e.g.
table/calculator; 3
(b) Any one correct change;
reason for diversity level;
explanation of how heather affects diversity; 3
–2 –1
(c) (i) Award two marks for 0.5 g m yr ;;
award one mark for answer without units
or 2.4 – 2.5 %; 2
(ii) Used for non photosynthesising/supporting organs;
eaten by grouse; 2
(iii) Younger plants have more shoots/provide more food;
Younger plants provide more cover;
Getting rid of old (unproductive) plants; max. 2
(d) (i) proteins/nucleic acids/amino acids/ATP/nucleotides;
(ii) ammonium/nitrate/nitrite;
– –
NH 4 NO 3 NO 2 [Formula must correspond if given] 1
(e) Organic material/proteins to ammonia/ammonium compounds; 1
by saprobiotic/putrefying bacteria;
ammonia to nitrite;
nitrite to nitrate;
by nitrifying bacteria/named bacteria; max. 4
(f) In older stands, greater proportion of/more nitrogen in plants;
more lost when burnt: 2
[20]
3. (a) Wood mouse; 1
(b) Decomposers/bacteria/fungi/saprophytes/saprotrophs/detritivores; 1
(c) Colonisation/pioneer species/examples from fig/seeds/fruits;
soil formation/improvement/change by organism;
succession/eq;
process repeated to climax community/forest; max. 3
diversity is reduced;
Sir George Monoux Sixth Form College 1
, (d) {trees form food source for many species/wide range of primary consumers;
{(primary consumers/named example/are eaten by other species)
{idea that trees are the basis of food chains/food webs;
productivity of area is reduced (with loss of trees);
so fewer organisms can be supported;
habitats are lost/ecological niches are lost (with each tree species lost); max. 3
[8]
4. (a) ‘Slash’ / cutting down trees reduces photosynthesis;
Reduces removal of carbon dioxide from atmosphere;
‘Burn’ combustion releases carbon dioxide;
OR ‘Slash’ cutting down trees removes respiring organisms;
Reduces removal of carbon dioxide into atmosphere;
‘Burn’ / combustion releases carbon dioxide; max 2
(b) (Before clearing) soil exists / already produced;
(After clearing) recolonisation by new plants / seeds;
(Brings about) change in environment / soil;
(Allows) succession;
(Leading to) climax (community); max 3
(c) 1 Ammonium compounds from proteins / amino acids urea / N-containing;
2 Converted into nitrite;
3 Into nitrate; [Reject: Incorrect sequence once]
4 By nitrifying bacteria / correctly named;
5 Nitrogen-fixing bacteria;
6 Fix nitrogen from atmosphere / air;
7 Nitrate taken up by plants;
8 Nitrogen needed for protein synthesis / plant growth; max 6
(d) Trees available as a sustainable resource;
Maintain habitats / niches / shelter;
Maintain diversity / avoid loss of species / protect endangered species.
Maintain stability (of ecosystem);
Maintain food chains / webs / supply of food;
Reduced loss of soil / erosion;
Reduced flooding;
Act as carbon sink / maintainO2and C02 balance reduce greenhouse effect
Reduce global warming;
Source of medicines;
[Ignore: eutrophication] max 4
[15]
5. (a) Tapes / string / axes laid out at right angles / grid area;
Method of obtaining random co-ordinates;
Do not allow “Use random number generator” 2
(b) (i) Decrease then remain constant;
From 200 cm / over 150 cm; 2
(ii) Oxygen decreasing because soil becomes more compacted/ not
replaced;
Decrease in oxygen leads to fewer aerobes surviving;
Respiration; max 2
(c) Anaerobic bacteria replace aerobic;
As oxygen decreased by aerobic bacteria;
Remove competition;
Sir George Monoux Sixth Form College 2
, Aerobic bacteria no longer able to survive in these conditions; max 3
Sir George Monoux Sixth Form College 3
volcanic/fresh rock/little/no soil/water/humus; 1
(ii) Colonisers erode rock/release minerals;
add (more) humus/increase nitrate content/organic material;
when colonisers die/decompose; max. 2
(b) More/less competition; 1
[4]
2. (a) Mark for principle of placing quadrats at random;
marks for detail -
(method of) marking area out with grid/using tapes;
acceptable method of generating random numbers; e.g.
table/calculator; 3
(b) Any one correct change;
reason for diversity level;
explanation of how heather affects diversity; 3
–2 –1
(c) (i) Award two marks for 0.5 g m yr ;;
award one mark for answer without units
or 2.4 – 2.5 %; 2
(ii) Used for non photosynthesising/supporting organs;
eaten by grouse; 2
(iii) Younger plants have more shoots/provide more food;
Younger plants provide more cover;
Getting rid of old (unproductive) plants; max. 2
(d) (i) proteins/nucleic acids/amino acids/ATP/nucleotides;
(ii) ammonium/nitrate/nitrite;
– –
NH 4 NO 3 NO 2 [Formula must correspond if given] 1
(e) Organic material/proteins to ammonia/ammonium compounds; 1
by saprobiotic/putrefying bacteria;
ammonia to nitrite;
nitrite to nitrate;
by nitrifying bacteria/named bacteria; max. 4
(f) In older stands, greater proportion of/more nitrogen in plants;
more lost when burnt: 2
[20]
3. (a) Wood mouse; 1
(b) Decomposers/bacteria/fungi/saprophytes/saprotrophs/detritivores; 1
(c) Colonisation/pioneer species/examples from fig/seeds/fruits;
soil formation/improvement/change by organism;
succession/eq;
process repeated to climax community/forest; max. 3
diversity is reduced;
Sir George Monoux Sixth Form College 1
, (d) {trees form food source for many species/wide range of primary consumers;
{(primary consumers/named example/are eaten by other species)
{idea that trees are the basis of food chains/food webs;
productivity of area is reduced (with loss of trees);
so fewer organisms can be supported;
habitats are lost/ecological niches are lost (with each tree species lost); max. 3
[8]
4. (a) ‘Slash’ / cutting down trees reduces photosynthesis;
Reduces removal of carbon dioxide from atmosphere;
‘Burn’ combustion releases carbon dioxide;
OR ‘Slash’ cutting down trees removes respiring organisms;
Reduces removal of carbon dioxide into atmosphere;
‘Burn’ / combustion releases carbon dioxide; max 2
(b) (Before clearing) soil exists / already produced;
(After clearing) recolonisation by new plants / seeds;
(Brings about) change in environment / soil;
(Allows) succession;
(Leading to) climax (community); max 3
(c) 1 Ammonium compounds from proteins / amino acids urea / N-containing;
2 Converted into nitrite;
3 Into nitrate; [Reject: Incorrect sequence once]
4 By nitrifying bacteria / correctly named;
5 Nitrogen-fixing bacteria;
6 Fix nitrogen from atmosphere / air;
7 Nitrate taken up by plants;
8 Nitrogen needed for protein synthesis / plant growth; max 6
(d) Trees available as a sustainable resource;
Maintain habitats / niches / shelter;
Maintain diversity / avoid loss of species / protect endangered species.
Maintain stability (of ecosystem);
Maintain food chains / webs / supply of food;
Reduced loss of soil / erosion;
Reduced flooding;
Act as carbon sink / maintainO2and C02 balance reduce greenhouse effect
Reduce global warming;
Source of medicines;
[Ignore: eutrophication] max 4
[15]
5. (a) Tapes / string / axes laid out at right angles / grid area;
Method of obtaining random co-ordinates;
Do not allow “Use random number generator” 2
(b) (i) Decrease then remain constant;
From 200 cm / over 150 cm; 2
(ii) Oxygen decreasing because soil becomes more compacted/ not
replaced;
Decrease in oxygen leads to fewer aerobes surviving;
Respiration; max 2
(c) Anaerobic bacteria replace aerobic;
As oxygen decreased by aerobic bacteria;
Remove competition;
Sir George Monoux Sixth Form College 2
, Aerobic bacteria no longer able to survive in these conditions; max 3
Sir George Monoux Sixth Form College 3
