WALT – Explain how we can use organisms to monitor pollution levels Pollution Indicators
What are pollution indicators? • The organisms in polluted water tell you that there is something wrong.
Examples of pollution indicators • Lichens are plants that grow in exposed places such as rocks or tree bark. • Air pollutants dissolved in rainwater, especially sulfur dioxide, can damage lichens, and prevent them from growing. • This makes lichens natural indicators of air pollution. For example:
Examples of pollution indicators • Some invertebrates like mayfly nymphs and rat-tailed maggots, are able to survive in polluted waters
This is what happens when a stream or river becomes polluted • Pollutant is added, which kills some living things. • Micro-organisms decompose them, they respire and use up the oxygen • Lack of oxygen kills other organisms, but a few species stay alive • As the water flows, oxygen levels gradually increase • Other living things recover too.
Sulphur dioxide, cities and lichens A scientist surveyed the distribution of lichens. She counted the number of different species that grew on tree trunks at various distances from the centre of a polluted city. She also measured how much sulfur dioxide there was in the air.
Sulfur dioxide, cities and lichens Think : Is the data continuous or discreet? What are you : changing? (x-axis) Measuring? (y-axis)
Graph Questions • What is the relationship between the number of species of lichen and the distance from the centre of the city. • Name one invertebrate that can survive where there is little oxygen and another one that needs normal clear water to live in
How you will be graded • Graph : 4 marks • 1 for scale • 1 for well labelled axes • 1 for plotting • 1 for line of best fit • Question 1 = 2 marks • Question 2 = 2 marks