What do the eras of the geologic time scale represent?

time between eras and biodiversity that exists on each period of the geological time

Explanation:

A geological era is a formal geochronological unit of the geological time scale that represents the time corresponding to the duration of an era, the equivalent chronostratigraphic unit comprising all the rocks formed at that time. The ages are one of the major divisions of geological time, they are subdivisions of the eons and they are divided into periods.

The three eras of the Phanerozoic eon variables, simplifying much, the three classic divisions of the history of the life of the planet:

1. Paleozoic represents the "age of fish"

2. Mesozoic the "age of reptiles"

3. Cenozoic the "age of mammals."

Traditionally they had been referred to as Primary Age, Secondary Era, Tertiary Era and Quaternary Era (currently the Quaternary is another period of the Cenozoic era). The passage from one era to another is defined by events of global mass extinctions, which entail a significant renewal of the biota of the planet, both marine and terrestrial; thus the passage from the Paleozoic to the Mesozoic is marked by the mass extinction of the Permian-Triassic and the passage from the Mesozoic to the Cenozoic by the mass extinction of the Cretaceous-Tertiary.