How do biomes affect animals?
Biomes have a direct impact on what kinds of animals that will thrive in a given biome and they also influence the course of biological evolution.
Biomes are largely determined by climate, which is a function of many variables; but moisture and temperature are two key factors. Moisture and temperature tend to be highest in the tropics and then drops off as latitude gets higher (i.e. towards the North and South poles).
The kind of biomes then determine which kinds of animals will thrive in a given region. This is biological evolution in action. For example, polar bears wouldn't last long in the tropical forests nor would tropical birds last long in the tundra. Each species is adapted to the biome it is best suited to and this is a kind of "weeding out" process - or survival of the fittest in any given biome.
When biomes undergo dramatic climate change (like what is happening now), animals must struggle to adapt and must either move to a biome more suited to their adaptations or possible go extinct in a particular area.