B2 predator prey cycle

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11 6

(a)  Snowy owls feed on lemmings.

The graph shows the number of snowy owl nests and the number of lemmings found on Bylot Island, Canada. snowy owl nests lemmings 24 22 20

4

18 16 number of nests

3

14

number of lemmings in thousands

12 10

2

8 6

1

4 2 0

0 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 year

The data in the graph suggests there is a pattern shown between the breeding of snowy owls and the numbers of lemmings. Describe this pattern and explain how it affects the populations of snowy owls and lemmings. ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... .............................................................................................................................................. [2]

© OCR 2015

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