1. © Oxford University Press 2011 IB2.31.2 Images Images

2. © Oxford University Press 2011 IB2.31.2 Images The woolly mammoth was widespread in northern regions of America and Europe, but became extinct about 10 000 years ago

3. © Oxford University Press 2011 IB2.31.2 Images Drawing of the extinct dinosaur Tyrannosaurus rex

4. © Oxford University Press 2011 IB2.31.2 Images The dodo lived on the island of Mauritius. The birds became extinct in the seventeenth century, not long after humans first landed there. Humans hunted them, and rats released by humans ate their eggs.

5. © Oxford University Press 2011 IB2.31.2 Images Dutch elm disease has wiped out more than 25 000 trees in the UK since 1967

6. © Oxford University Press 2011 IB2.31.2 Images The red squirrel has been largely replaced in the UK by the grey squirrel, which is more efficient at gaining resources such as food