Characteristics of biological evolution in Precambrian.

1. Development of protobacteria and algae. The oldest known fossil was found in fig trees in South Africa, which has a history of more than 3 billion years. They are tiny (5 ~ 25 microns) spherical and filamentous, and are considered as unicellular bacteria and algae. Recently, fossils that may be bacteria and algae have also been found in Anshan Group, China. These Archean (to Proterozoic) creatures are simple and basically asexual life forms, and they have no real nucleus, so they are called prokaryotic cells. They feed on organic matter, also known as heterotrophs.

2. The emergence of eukaryotes. Truly unquestionable eukaryotes were found in Beikequan Formation in North America in 65.438+0.35 billion years, and green algae fossils were also found in Wumishan Formation in North China in about 65.438+0.3 billion to 65.438+0.2 billion years. Eukaryotes appeared and developed about 2 billion to 65.438+0.9 billion years ago.

3. The appearance of metazoa and the transition from pre-Phanerozoic to Phanerozoic. At the end of Precambrian, the appearance of large-scale stable blocks, the vast shelf shallow sea after glacial period, the significant increase of oxygen content in the atmosphere and the existence of possible effective ozone shielding (Barker and Marshall, 1965) led to the appearance and development of metazoa.