Answer:
The Earth is essentially a closed system; it obtains lots of energy from the Sun but the exchange of matter with the outside is almost zero. Isolated systems can exchange neither energy nor matter with an outside system.
The Precambrian was originally defined as the era that predated the emergence of life in the Cambrian Period. It is now known, however, that life on Earth began by the early Archean and that fossilized organisms became more and more abundant throughout Precambrian time.
