94. The charts show some results from a survey of water quality and species diversity at nine sites
along a stream on the Isle of Wight in 1988. Sewage was discharged into the stream at certain
points.
K ey
In d iv id u a ls p e r k ic k s a m p le
M o re th a n 1 0 0 1 0 to 9 9 1 to 9
M a y fly
la rv a e
H o g lic e
S h rim p s
0 1 2 3 4 5 6 7 8 9
D is ta n c e d o w n th e s tre a m
4 0
3 5
3 0
C o n c e n tra tio n o f
2 5
a m m o n iu m io n s /
m g d m –3 2 0
1 5
1 0
5
0
0 1 2 3 4 5 6 7 8 9
D is ta n c e d o w n th e s tre a m
S ite s w h e re s e w a g e w a s d is c h a rg e d
(a) The animals were collected by kick sampling. In this technique, a net is held in the water.
Animals disturbed by kicking the streambed are collected inside the net.
Describe one precaution that should be taken to ensure that valid comparisons could be
made between samples taken from different sites.
.....................................................................................................................................
.....................................................................................................................................
(1)
(b) List the species in order of their tolerance to pollution by sewage.
Most tolerant ...................................................................
Medium tolerance ...................................................................
Least tolerant ................................................................... (1)
1
,S (c) Explain why the concentration of ammonium ions was high in the samples of water taken
from the sites where sewage was discharged into the stream.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
S (d) In 1989 all houses in the area were connected to drains and so sewage no longer entered
the stream. Following this, the oxygen concentration in the stream increased.
Explain why.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 7 marks)
–2 –1
95. The diagram shows the energy flow through a freshwater ecosystem. All units are kJ m year .
L ig h t e n e rg y a b s o rb e d
b y p la n ts
6
1 .7 × 1 0
P ro d u c e rs
87402
50 303 22 953
14 146
P rim a ry
7938 co n su m ers 4599
1609
S e c o n d a ry
1328 co n su m ers 193
B ox B
P ro c e ss A
2
, (a) Name
(i) process A;
...........................................................................................................................
(1)
(ii) the group of organisms represented by box B.
...........................................................................................................................
(1)
(b) Calculate the percentage efficiency with which light energy is transferred to energy in
producers. Show your working.
Answer ........................................
(2)
S (c) Describe the effect of light energy in the light-dependent reaction of photosynthesis.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
S (d) If a plant is kept in the dark it is still able to produce carbohydrates, as long as it is
provided with two products of the light-dependent reaction of photosynthesis. Give the
name of these products and explain their function in the light-independent reaction of
photosynthesis.
Name ..........................................................................................................................
Function .....................................................................................................................
.....................................................................................................................................
Name ..........................................................................................................................
Function ......................................................................................................................
.....................................................................................................................................
(4)
(Total 10 marks)
3
along a stream on the Isle of Wight in 1988. Sewage was discharged into the stream at certain
points.
K ey
In d iv id u a ls p e r k ic k s a m p le
M o re th a n 1 0 0 1 0 to 9 9 1 to 9
M a y fly
la rv a e
H o g lic e
S h rim p s
0 1 2 3 4 5 6 7 8 9
D is ta n c e d o w n th e s tre a m
4 0
3 5
3 0
C o n c e n tra tio n o f
2 5
a m m o n iu m io n s /
m g d m –3 2 0
1 5
1 0
5
0
0 1 2 3 4 5 6 7 8 9
D is ta n c e d o w n th e s tre a m
S ite s w h e re s e w a g e w a s d is c h a rg e d
(a) The animals were collected by kick sampling. In this technique, a net is held in the water.
Animals disturbed by kicking the streambed are collected inside the net.
Describe one precaution that should be taken to ensure that valid comparisons could be
made between samples taken from different sites.
.....................................................................................................................................
.....................................................................................................................................
(1)
(b) List the species in order of their tolerance to pollution by sewage.
Most tolerant ...................................................................
Medium tolerance ...................................................................
Least tolerant ................................................................... (1)
1
,S (c) Explain why the concentration of ammonium ions was high in the samples of water taken
from the sites where sewage was discharged into the stream.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
S (d) In 1989 all houses in the area were connected to drains and so sewage no longer entered
the stream. Following this, the oxygen concentration in the stream increased.
Explain why.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 7 marks)
–2 –1
95. The diagram shows the energy flow through a freshwater ecosystem. All units are kJ m year .
L ig h t e n e rg y a b s o rb e d
b y p la n ts
6
1 .7 × 1 0
P ro d u c e rs
87402
50 303 22 953
14 146
P rim a ry
7938 co n su m ers 4599
1609
S e c o n d a ry
1328 co n su m ers 193
B ox B
P ro c e ss A
2
, (a) Name
(i) process A;
...........................................................................................................................
(1)
(ii) the group of organisms represented by box B.
...........................................................................................................................
(1)
(b) Calculate the percentage efficiency with which light energy is transferred to energy in
producers. Show your working.
Answer ........................................
(2)
S (c) Describe the effect of light energy in the light-dependent reaction of photosynthesis.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(2)
S (d) If a plant is kept in the dark it is still able to produce carbohydrates, as long as it is
provided with two products of the light-dependent reaction of photosynthesis. Give the
name of these products and explain their function in the light-independent reaction of
photosynthesis.
Name ..........................................................................................................................
Function .....................................................................................................................
.....................................................................................................................................
Name ..........................................................................................................................
Function ......................................................................................................................
.....................................................................................................................................
(4)
(Total 10 marks)
3
