Scaling the heights.
The mountain environment is harsh one, and the higher the altitude, the harsher it becomes. The temperature falls by about 1 c for every 150 m (500ft), the winds blow harder, and the atmosphere becomes thinner and less rich in oxygen. Thin soils, high winds, and low temperatures cause many plants to grow in a stunted form, giving rise to dwarf varieties that can survive mountain conditions. Most mountains are covered in snow for some of the time, and conditions can closely resemble those in semi-polar, or tundra, regions. Several species of animals and plants adapted for life in tundra were left behind when the melting ice sheets retreated northwards at the end of the last Ice Age. In the mountains, these species found conditions very similar to those of the tundra, and they were able to remain there, sometimes evolving in isolation from other populations. This is one of the reasons why mountain life varies so much from region to region. Most of the examples seen here are found in northern Europe.