Succession
1.	The diagram shows a profile along a transect showing succession on some coastal sand dunes.
Point	A	B	C	D	
Index of diversity	1	2.3	5.4	6.1	

(a)	What data must be collected in order to be able to calculate an index of diversity of plants at one of the points along the transect?
(2)
(b)	Suggest an explanation for the trend in diversity along the transect.
(3)
2.	In the process of succession, land on a newly formed volcanic island will be gradually colonised. Over time, changes in the composition of the plant and animal communities will occur until eventually no further change takes place.
(a)	What term is used to describe the final stable community at the end of a succession?
(1)

(b)	Explain why one community is gradually replaced by another during succession.
(2)
(c)	Describe how each of the following farming practices influences the process of succession.
(i)	regular grazing by sheep
(ii)	ploughing fields each year
(3)

3.	(a)	Explain two ways in which the expanding human population is placing increasing demands on natural communities.
(2)

(b)	Under natural and suitable conditions, bare soil would eventually become covered by a woodland community. Explain how farming practices prevent this from happening.
(4)

(c)	The graph shows the number of species from three insect groups which are thought to be extinct or close to extinction in three different habitats in the UK.

(i)	Farming often produces temporary areas of bare soil on which colonisation may start, but these data show that many species of insect associated with the type of community that develops in this habitat are endangered. Suggest why.
(3)

(ii)	Suggest explanations for the differences between the data for live trees and dead trees.
(3)

4.	The diagrams show stages in a succession from a lake to an oak wood.

1 Aquatic plants	2 Reeds with	3 Sledges
	underground
	stems

4 Tussock-building	5 Alder trees	6 Oak trees
(a)	(i)	What is the name used to describe the final stage in a succession such as this?
(1)
(ii)	The aquatic plants and the reeds both contribute to the formation of soil.
Suggest how the aquatic plants and reeds contribute to raising the soil level.
(2)

S	(iii)	The sedges are rooted in waterlogged soil. Their stems contain a spongy tissue through which air can reach the roots.
Explain how this is important for the absorption of mineral ions by the sedges.
(3)
(b)	Explain why the ecosystem is likely to have more species in the later stages than in the earlier stages of succession.
(2)