proterozoisissa

The Proterozoic Eon is the most recent eon of the Precambrian Supereon, spanning from 2.5 billion to 541 million years ago. It is a vast period of Earth's history characterized by significant geological, atmospheric, and biological transformations. Geologically, the Proterozoic saw the formation and breakup of supercontinents, including Rodinia and Pannotia. Mountain-building events and extensive volcanic activity were common. The Earth's atmosphere underwent a profound change during this eon with the Great Oxidation Event, which began in the early Proterozoic. This event, driven by the evolution of oxygenic photosynthesis in cyanobacteria, gradually increased the oxygen content of the atmosphere.

Biologically, the Proterozoic is notable for the emergence of eukaryotic cells, which possess a nucleus and other membrane-bound organelles. This marked a significant step in cellular complexity. Later in the eon, multicellular life began to appear, culminating in the Ediacaran biota, a diverse assemblage of soft-bodied organisms that represent the earliest known complex multicellular life forms. The Proterozoic Eon laid the groundwork for the explosion of life seen in the subsequent Phanerozoic Eon, particularly with the evolution of sexual reproduction, which facilitated greater genetic diversity and evolutionary innovation.