Question

which option best distinguishes the precambrian and phanerozoic eons?
life was rare and simple in the precambrian and then underwent a sudden increase in diversity in the phanerozoic.
both the precambrian and phanerozoic eons had diverse life adapted to different environments.
life was rare and simple in the phanerozoic and then underwent a sudden increase in diversity in the precambrian.
there was diverse life in the precambrian, but a mass extinction wiped it all out in the phanerozoic.

Explanation:

The Precambrian eon (which makes up about 88% of Earth's history) had mostly simple and rare life forms like bacteria, archaea, and simple multicellular organisms. The Phanerozoic eon (the last 541 million years) saw a sudden increase in biodiversity with the Cambrian explosion (a rapid diversification of life - forms).

• The second option is wrong because the Precambrian did not have diverse life adapted to different environments like the Phanerozoic.
• The third option has the time - order reversed.
• The fourth option is incorrect as there was not a high level of diverse life in the Precambrian to be wiped out in the Phanerozoic.

Answer:

Life was rare and simple in the Precambrian and then underwent a sudden increase in diversity in the Phanerozoic.