noun
biotope
A German loanword used in ecology and landscaping for a small, self-contained habitat, often a garden pond or mini-ecosystem.
from German Biotop
学校の庭にビオトープを作って、メダカを飼っている。
We built a biotope in the schoolyard and keep killifish there.
生態系 is the general term for 'ecosystem', while ビオトープ refers specifically to a designed or preserved small-scale habitat.
Borrowed from German 'Biotop', itself from Greek 'bios' (life) and 'topos' (place).