A system of living organisms interacting with each other and their physical environment. The boundaries of what could be called an ecosystem are somewhat arbitrary, depending on the focus of interest or study. Thus, the extent of an ecosystem may range from very small spatial scales to, ultimately, the entire Earth. (IPCC)
A biome /ˈbaɪoʊm/ is a formation of plants and animals that have common characteristics due to similar climates and can be found over a range of continents. Spanning continents, Biomes are distinct biological communities that have formed in response to a shared physical climate. Biomes are distinct from habitats, because any biome can comprise a variety of habitats. A biome contrasts with a microbiome. A microbiome is also a mix of organisms that coexist in a defined space, but on a much smaller scale. For example, the human microbiome is the collection of bacteria, viruses, and other microorganisms that are present on a human.
Source: Wikipedia - Biome