Why can many ecosystems exist in one biome?

many ecosystems can exist in one biome which is because it is just a geographic area where ecosystems exist. most commonly grouped biomes are desert, deciduous forests, coniferous forests, arctic tundra, tropical rainforests, grasslands, and taigas. There are also marine and freshwater ecosystems that could be considered as water biomes.

separation of church and state? not sure what you mean.