Lichens are found growing on trees, walls, rocks and soil. Fig. 9.1 shows a lichen of the genus Usnea. Usnea can tolerate only low concentrations of sulfur dioxide and does not grow in places where the air is polluted with sulfur dioxide. [Figure 9.1] Usnea is composed of a mixture of two types of cell: • photosynthetic cells that are classified in the kingdom Protoctista • fungal cells that are classified in the kingdom Fungi.

1. (a)Outline the characteristic features of the kingdoms Protoctista and Fungi.[4]
2. (b)(i)Xanthoria is a lichen that can grow in places where there is a high concentration of sulfur dioxide in the air, for example in towns where homes, factories and vehicles burn fuels. Fig. 9.2 shows a lichen of the genus Xanthoria. [Figure 9.2] A student planned a method to measure the relative abundance of Usnea and Xanthoria on trees along a transect from the town centre at 0 km to unpolluted countryside at 4 km. Suggest why measuring the relative abundance of the two types of lichen gives information that is useful for conservation.[3]
3. (b)(ii)Although a large biodiversity of lichens can be found in a range of habitats, most people ignore them. Outline why forms of life that are usually ignored, such as lichens, should be conserved.[2]

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