1. Answers should be written in continuous prose. Credit will be given for biological accuracy, the
organisation and presentation of the information and the way in which the answer is expressed.
The diagram shows part of a system designed to meet all the basic needs of a family of four
living in the tropics.
C r o p p la n ts C ro p w a s te
S o lid w a s te
u s e d a s f e r tilis e r
C a ttle a n d
U rin e a n d fa e c e s
c h ic k e n s
F e rm e n te r L iq u id w a s te A lg a e in
c o n ta in in g s h a llo w p o n d
b a c te ria
C a rb o n
F is h
d io x id e
G as u sed as fu e l fo r
c o o k in g a n d lig h tin g
U rin e a n d
faec es
H um ans
(a) The processes which naturally form part of the nitrogen cycle can make nitrogen
contained in urine and faeces available to crop plants. Describe how these processes
occur.
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.....................................................................................................................................
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.....................................................................................................................................
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(6)
Sir George Monoux Sixth Form College 1
, (b) Explain the advantage in this system of:
(i) growing leguminous plants such as groundnuts or beans;
...........................................................................................................................
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...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
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(4)
(ii) stocking the pond with fish that feed on algae rather than with carnivorous fish.
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...........................................................................................................................
(3)
(Total 13 marks)
2. Spruce trees produce very large numbers of seeds. Most of these seeds die immediately,
releasing nitrogen compounds into the soil. Swedish scientists investigated the effects of this on
the growth of pine seedlings, in areas where the forest floor was free of moss plants and in areas
where moss plants grew.
(a) Describe the part played by soil bacteria in making the nitrogen in compounds in the dead
spruce seeds available to pine seedlings.
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.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
Sir George Monoux Sixth Form College 2
, (b) In areas where the forest floor was free of moss plants, the pine seedlings grew better in
plots with added spruce seeds than they did in control plots. In areas in which moss plants
grew, the difference in growth of the pine seedlings in plots with added spruce seeds was
not statistically significant from those in the control plots. Suggest an explanation for the
effect of the moss plants on the growth of the pine seedlings.
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.....................................................................................................................................
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(2)
(Total 5 marks)
3. Heather is a woody plant found in many moorland areas on higher ground in Britain. Grouse are
chicken-sized birds which feed on the young shoots of heather. On many moorlands, the heather
is managed to produce better conditions for grouse. This involves burning large areas. After
burning, heather goes through the cycle of growth described below.
Pioneer phase New plants grow either from
0-7 years seed or from stem bases
undamaged by fire.
Building phase Phase of rapid growth
7-15 years producing dense cover of
heather plants.
Mature phase Plants still growing but gaps
15 - 25 years start to appear in the canopy.
Degenerate phase Branches break. Central part
25+ years of plant dies although outer
branches may remain alive.
Sir George Monoux Sixth Form College 3
, Table 1 summarises some data collected from a study of heather plants of different ages.
Age/years Total Biomass of green Percentage cover Light at ground level
2 –2 as percentage of light
biomass/g m shoots/g m
in open
5 287 78 10 84
10 1508 203 85 5
20 1924 208 76 22
30 1043 n/a 34 56
Table 1
Key:
n/a = figures not available
(a) To determine the total biomass, quadrats were used to collect the heather samples.
Describe the procedure you would have used to place these quadrats.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(b) Describe how and explain why the diversity of plant species would be likely to change
during the cycle of growth of the heather.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
Sir George Monoux Sixth Form College 4
organisation and presentation of the information and the way in which the answer is expressed.
The diagram shows part of a system designed to meet all the basic needs of a family of four
living in the tropics.
C r o p p la n ts C ro p w a s te
S o lid w a s te
u s e d a s f e r tilis e r
C a ttle a n d
U rin e a n d fa e c e s
c h ic k e n s
F e rm e n te r L iq u id w a s te A lg a e in
c o n ta in in g s h a llo w p o n d
b a c te ria
C a rb o n
F is h
d io x id e
G as u sed as fu e l fo r
c o o k in g a n d lig h tin g
U rin e a n d
faec es
H um ans
(a) The processes which naturally form part of the nitrogen cycle can make nitrogen
contained in urine and faeces available to crop plants. Describe how these processes
occur.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(6)
Sir George Monoux Sixth Form College 1
, (b) Explain the advantage in this system of:
(i) growing leguminous plants such as groundnuts or beans;
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(4)
(ii) stocking the pond with fish that feed on algae rather than with carnivorous fish.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
(3)
(Total 13 marks)
2. Spruce trees produce very large numbers of seeds. Most of these seeds die immediately,
releasing nitrogen compounds into the soil. Swedish scientists investigated the effects of this on
the growth of pine seedlings, in areas where the forest floor was free of moss plants and in areas
where moss plants grew.
(a) Describe the part played by soil bacteria in making the nitrogen in compounds in the dead
spruce seeds available to pine seedlings.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
Sir George Monoux Sixth Form College 2
, (b) In areas where the forest floor was free of moss plants, the pine seedlings grew better in
plots with added spruce seeds than they did in control plots. In areas in which moss plants
grew, the difference in growth of the pine seedlings in plots with added spruce seeds was
not statistically significant from those in the control plots. Suggest an explanation for the
effect of the moss plants on the growth of the pine seedlings.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
(Total 5 marks)
3. Heather is a woody plant found in many moorland areas on higher ground in Britain. Grouse are
chicken-sized birds which feed on the young shoots of heather. On many moorlands, the heather
is managed to produce better conditions for grouse. This involves burning large areas. After
burning, heather goes through the cycle of growth described below.
Pioneer phase New plants grow either from
0-7 years seed or from stem bases
undamaged by fire.
Building phase Phase of rapid growth
7-15 years producing dense cover of
heather plants.
Mature phase Plants still growing but gaps
15 - 25 years start to appear in the canopy.
Degenerate phase Branches break. Central part
25+ years of plant dies although outer
branches may remain alive.
Sir George Monoux Sixth Form College 3
, Table 1 summarises some data collected from a study of heather plants of different ages.
Age/years Total Biomass of green Percentage cover Light at ground level
2 –2 as percentage of light
biomass/g m shoots/g m
in open
5 287 78 10 84
10 1508 203 85 5
20 1924 208 76 22
30 1043 n/a 34 56
Table 1
Key:
n/a = figures not available
(a) To determine the total biomass, quadrats were used to collect the heather samples.
Describe the procedure you would have used to place these quadrats.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(b) Describe how and explain why the diversity of plant species would be likely to change
during the cycle of growth of the heather.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
Sir George Monoux Sixth Form College 4
