When many types of organisms become extinct at the same time

The vast majority of species that have ever lived went extinct sometime other than during one of the great mass extinction events.

Explanation:

Since the Cambrian Explosion, there have been five mass extinctions, each of which is named for the geological period in which it occurred, or for the periods that immediately preceded and followed it. The first mass extinction is called the Ordovician-Silurian Extinction.

Explanation:

i would say the prokaryotic cells the prokaryotic cells are less complex, are usually found only in unicellular organisms and have more limited capabilities than eukaryotic cells.