the characteristic plants and animals...

[Goooodman]

This text below is the definition of biome form the Oxford Advanced Learner’s Dictionary.
the characteristic plants and animals that exist in a particular type of environment, for example in a forest or desert.
What are the characteristic plants and animals?

 

[Uncle Jack]

The ones that are commonly found there, that are generally associated with that particular environment. Since "biome" tends to be used for very broad categories, such as tropical rainforests, biomes generally consist of thousands of species.