B3 LIFE ON EARTHLesson 5: Environmental Indicators

OBJECTIVESMUST explain how environmental change can be monitored

SHOULD interpret data to investigate environmental change

KEY WORDS You need to be able to define the following:

Non-living indicator Living indicator Phytoplankton Lichens

TEXTBOOK ANSWERS1) By monitoring using living or non-living

indicators.2) Living: mayfly, lichens, phytoplankton. Non-living: nitrate level, temperature, carbon dioxide level.

3) Because they are at the start of many aquatic food chains.

4) Different lichens are sensitive to different pollutants; by studying the whole community of lichens, a better picture of the overall level of pollution can be gathered.

TEXTBOOK ANSWERS5) The nitrate concentration in the stream

alongside the farmland rose rapidly from just above zero to 18 mg/litre in the month following the application of the nitrate fertiliser to the farmland; the levels of nitrate in the stream then fell back to nearly zero over a period of about 7 months.

6) They give only a snapshot of what is going on in an environment; for example, if the nitrate level in the stream from Figure 5 were taken in December, January or February, the stream would seem unpolluted, because the pollution occurred only periodically.

WORKSHEET ANSWERSActivity 1 (Low demand)1) a) A living indicator is an organism that

responds in a particular way to environmental change in its habitat.A non-living indicator is a way of monitoring the environment that shows the level or value of a particular physical factor in the environment under study.b) They are very sensitive to changes in their environment.

2) Living: A, B, F; Non-living: C, D, E

WORKSHEET ANSWERSActivity 2 (Standard demand)1) In 1975 there was no growth of lichens that grow in the

most polluted air, but there were lichens that grow in less polluted air, so sulfur dioxide levels were likely to be low. In 1980 lichens that could withstand high levels of pollution dominated and there were no lichens that could live only in unpolluted air. The sulfur dioxide levels were likely to be high at this time. In 1985 the lichens were those that need cleaner air, so sulfur dioxide levels are likely to have dropped again. In 1990 there were hardly any lichens that grow in highly polluted areas. The population of lichens that need unpolluted air was high. The sulfur dioxide pollution is likely to have been low in the years preceding 1990.

2) It was probably built between 1976 and 1979; the pollution level was shown to be higher in 1980.

3) Lichens take a long time to grow so can show how polluted the environment has been over a long period.

WORKSHEET ANSWERSActivity 3 (High demand)

a) A digital thermometer could be used to measure the temperature of the water, perhaps automatically set to record the temperature every hour over a long period of time − before the factory opens as well as afterwards, to show any changes; or thermometers could be used upstream and downstream of the factory for comparison.b) Survey the invertebrate population initially and then each month; some individual species that are particularly sensitive to temperature change could be chosen as indicator species to monitor more regularly.c) Species sensitive to pollution could be used as indicators of whether or not the water was becoming more polluted; non-living indicators could also be used, testing for the most likely pollutants from the factory; samples could be taken at different distances downstream from the factory for comparison.