Unit 3 Life on Earth
Topic 5 Human Impact on the Environment
National 5
Homework 2
1. The diagram shows how a non-biodegradable insecticide passes through a food
chain in a Scottish fresh-water loch.
(a)
Describe one way in which the insecticide could get into the loch water.
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KU1
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(b) (i) The diagram shows the number of times the insecticide becomes concentrated at
each stage of the food chain.
If the concentration of insecticide in the plant plankton is 0.025 ppm what would
be the expected concentration in the osprey?
Space for calculation
PS1
__________ ppm
Unit 3 Life on Earth
Topic 5 Human Impact on the Environment
National 5
(b)(ii) Explain why insecticide becomes more concentrated in carnivores at the top of the
food chain.
KU2
(c)
Insecticides are chemicals used extensively in agriculture.
Name ONE other types of chemical used to treat crops and explain why they are
used.
KU1
Chemical: _____________________
Use: ___________________________________________________
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2. (a) The increasing world population requires an increased supply of food.
Pesticides are chemicals which can be used to increase food supply.
However, their use can lead to instability in food webs.
Explain this effect.
(b)
KU1
When fertilisers are used in agriculture they can pollute rivers and lochs
causing algal blooms.
(i)
What is an algal bloom?
KU1
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(ii)
Describe the effects an algal bloom might have on a loch.
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KU3