Niche, adaptation and natural selectionEdexcel A-Level Biology A: Mind map

Exam questions on Niche, adaptation and natural selection

1. Marram grass grows on exposed sand dunes, where water drains away quickly and strong winds dry the air. Its leaves are rolled lengthways, with the stomata on the inner surface in pits lined with hairs. It also has long roots that reach deep into the sand.
   Explain how the rolled leaves and stomata in hair-lined pits help marram grass to survive on the dunes.2 marks
2. Male emperor penguins incubate their eggs through the Antarctic winter. The males huddle tightly together and take turns to stand at the cold outer edge of the huddle. Each penguin has densely packed, overlapping feathers and a thick layer of fat under the skin. During incubation the males fast and lower their metabolic rate.
   Explain how huddling increases the chance of a male penguin surviving the winter and breeding successfully.2 marks
3. In the 1950s warfarin, a poison that causes fatal internal bleeding, was used to kill brown rats on farms in Britain. Within a few years warfarin-resistant rats were found in some areas. Resistance is caused by an allele of one gene that arose by mutation and is inherited. Before warfarin was used, the allele was very rare in the rat population.
   Explain how the frequency of the resistance allele in the rat population increased.3 marks