A proper ecosystem needs clean air, water, food, sunlight, and other animals to support each other
Most planets have no water because it's too hot and others are too cold. The atmospheres are too weak or too strong. These planets aren't fit enough to sustain life
In order to live most life needs fuel (food, water, and sunlight)
In chemistry an object can go through a physical change or a chemical change. A chemical change means you cant go back to how it was before. Physical change means you can go back to how the object was before.