How does a biome differ from a community?
Biomes are a group of ecosystems, and caracterized by biogeographical constraints.
Communities are groups of species in the same place, at the same time.
A biome regroup several ecosystems that have the same structure. Biomes are caracteristic of a biogeographic zone ate the continental scale (and its climatic conditions) and are qualified depending on the animals and plants that are predominants in this zone.
The major types are : Aquatic, deserts, forests, grasslands and tundra (thought, not everybody agrees on this, depending which environmental conditions are used to classify them). Each of these major types can be subdivided (For example, marine and freshwater biome for the Aquatic type / tropical and temperate for the Forest type).
A community is a groupe of species at a given time, in a given place. For example: the community of fish in the Northern Sea. The time and space scale can vary from a very local to a regional one.
A community structure depends on interspecific relationships (predation, competition, ...)