In a general sense, biospheres are any closed, self-regulating systems containing ecosystems. Planet Earth’s biosphere is considered closed, although it does receive energy from the Sun, and some space dust enters our atmosphere, as well as the odd meteorite. Those externalities apply to all biospheres, and life cannot live without solar energy, so it is a redundant point.
Our biosphere can be seen as a self-perpetuating, steady-state system, when viewed long term. On a micro scale, it is a large set of small ecosystems in constant flux, but collectively they contribute to a remarkable whole. Most species keep on surviving for a very long time. Super volcanoes and asteroid collisions can interrupt things. Some species can fail to continue due to the evolution of other species, local climactic changes, and disasters.
But for the most part, Earth has a long-term, happily balanced Biosphere, where changes are slow and extinctions are few. We have gone from a very small number of species and types of species at the beginning of life on Earth, to many millions of species and a great variety as well.
Monkeys and apes, despite their higher intelligence, were a normal part of the balance, just like relatively stupid animals like slugs are as well. Intelligence has not upset the balance of things, not from apes, not from elephants, not from dolphins, crows or octopi.
Even proto-humans were okay. Even hunter-gatherer humans were okay. Native Americans (mostly) successfully integrated well with the existing habitat, and lived in a harmonious balance with the native flora and fauna.
I’m not saying that our beautifully balanced biosphere was by design, but we got there and Earth should have expected billions more years of the same. But that “design” or “steady state” has been upset by a single emerging factor that feels like it came from outside the system. Human civilization, its growth, and its belief in its superiority over everything else. That is destroying species, destroying habitats, and threatening the planet. That is the odd one out. That is the infiltrator that our planet should have antibodies against. But it doesn’t, and humans won’t stop.
Well, unless some of us fight and a division of humans sabotages the rest.