A ecosystem is called a ecosystem because the word eco means environment. The system part is telling you that there is a certain cycle or system.
A forest ecosystem is one in which considerably tall and dense trees have high density,that also support many animal species within it.
they aren't important
Any ecosystem is in a state of flux. stability is relative, and based on that nothing is really stable. ocean ecosystems are in a state of change the same as forest ecosystems.. neither can be said...
a tundra eco system is made up of only short stubby plants and not many animals