Question

The Proterozoic era is defined by the following events: eukaryotic cells first seen stable continents first bacteria fossils the Cambrian explosion oxygen building up in atmosphere

Answer 1

eukaryotic cells first seen
stable continents
oxygen building up in atmosphere

Answer 2

The events that occurred in the Proterozoic era s defined by events like:

The eukaryotic cells were first seen in the this era and oxygen also started building up in the environment. The first advanced single celled, eukaryotes along with the multicellular life evolved.

The oxygen that was released in the atmosphere was produced as a result of photosynthesis.