Both the Arctic (North Pole<span>) and the Antarctic (South </span>Pole<span>) are cold because they don't </span>get<span> any direct sunlight. The Sun is always low on the horizon, even in the middle of summer. In winter, the Sun is so far below the horizon that it doesn't come up at all for months at a time.</span>
Answer:
Vegetation types
Explanation:
In the case of biomes, which are perhaps the most commonly used classification scheme in physical geography, vegetation is the principal indicator to delinate the different zones and their subtypes.
Even if both vegetation and fauna define a biome, and a sub-biome, because vegetation is more pervasive than fauna, it becomes the principal indicator in practice.
Maybe the fact that Earth is over 14 million years old may be a factor.