Boreskov

PL‐3EUKARYOTES AND THE HISTORY OF THEIR APPEARANCE IN THE BIOSPHERERozanov A.Yu.Borissiak Paleontological Institute of the Russian Academy of Sciences, Moscow, Russia1. It is obvious that organization level of organisms is correlated with environmentalparameters.2. The appearance of Cyanobacteria in the geological record and latter appearance ofunicellular eukaryotes, multicellular eukaryotes, then Metaphyta and Metazoadetermine the amount of atmospheric oxygen, temperature and other parameters.3. To define the organization level of fossil organisms from the ancient rocks, oftenmetamorphized, is one of the most difficult problems.4. A simple morphology (sphere, dumbbell, thread, etc.) hampers the fossil identification.5. The size of fossils, complicated wall structure, presence of pores and apophyses givesome chance for recognition of eukaryotic organisms.6. Important data come from the analyze of the material forming fossils. For instance, thecontraction folds of large spherical forms quite confidently prove the pectic nature ofenvelopes.7. The major importance of eukaryotic origin is explained by the fact that eukaryotes areundoubted aerobic organisms.8. At present the following order of organisms origin seems the most plausible; to differentextent this is supported by actual material. Recently, some dating have become olderand older:3.5 Ga – possible cyanobacteria (Australia);3.0 Ga – reliable and numerous finds of cyanobacteria (Karelia) [B.V. Timofeev’s finds ofprobable eukaryotes (trichomes and large spheres) and forms with apophyses orcontractions folds have the same age];2.4 Ga – multicellular algae (Metaphyta) in weathering crusts;2.0 Ga – protists and fungi, and possible Metazoa1.6 Ga – Coelomata.9. The data on biomarkers completely correspond to the above mentioned sequence oforganism appearance.10