Answer:
population → community → ecosystem → biosphere
"Habitat" doesn't quite fit in this list. "Species" likewise doesn't fit well, but I suppose it could go at the start of the list.
Species: members of the same, well, species. Homo sapiens, for example; a group of humans is a species.
Population: similar to species, but used to describe an individual group of organisms. Like if there are 30 dogs in my house, that's a population of 30, though the species probably is made up of thousands.
Community: a group of biotic factors (remember, living, not nonliving) in the same space.
Ecosystem: a combination of all those biotic factors, plus abiotic factors like rocks, wind, sun, et cetera
Biosphere: the whole Earth.