Truuuueeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee
I believe it'd decrease. Many species would either take a major population hit depending on the range of the fire or some species would have to move from the area entirely.
A. It has mass.
Air is matter, and can't be seen thus not all matter can be seen.
Any liquid or gaseous is matter (water, air, etc.)
Since it can be liquid or gaseous it doesn't have to maintain it's shape and size to be matter.
Yes we have to maintain homeostasis so our bodies have to adapt to Mother Nature