All questions needed is an estimate of the clover p
5 A scientist sampled the dissolved oxygen concentration
of water in a stream as it passed an industrial complex:
14
12
10
4
2
0 500 1000 1500 2000
distance from industrial complex (m)
O State where the oxygen concentration in the
a
water was at its highest level.
b State where the oxygen concentration in the
water was at its lowest level.
O Calculate the percentage increase in dissolved
c
to
d
e
as
oxygen content between the lowest and the
highest recorded levels.
Explain what is meant by an indicator species.
More polluted water contains less dissolved
oxygen. The scientists found no mayfly nymphs
within 200 m of the industrial complex; many
were found 2 km downstream. Explain how
mayfly nymphs can be used to show that the
industrial complex was polluting the stream.
