The answer is probably air.
Explanation:
Biome and the ecosystem are the words that are sometimes applied interchangeably to explain a particular kind of environment.
The biome represents the geographical region that has the same kind of ecological atmosphere, climate and mostly consistent collection of the species and it is made of a large number of ecosystems.
An ecosystem represents a particular element of the biome and a species that nearly interact in it.
Thus the biome is the collection of various types of ecosystems.
Prey or predation is a biological interaction where a predator (an organism, often an animal) kills and eats its prey (another organism).
Like a mouse getting caught and eaten by a bird of prey (Eagles, hawks, etc.)