Mountains are in general a much tougher place to life than equivalent lowland habitats, partly due to the lower temperatures and harsher weather. At very high altitudes there is also less oxygen and carbon dioxide in the air, making life difficult for both animals and plants. Soils are thin or non-existent on steep mountain slopes, which restricts the types of plants that can grow. The uppermost slopes of the tallest mountains may be completely barren of plant-life.

More...