Abstract:
The irreversible evolution of the Earth and periodic fluctuations of the climate and environment are major forces that drive biological evolution. Irreversible evolution is exemplified by the cooling of the Earth's interior, with periodic fluctuations of the internal temperature, changing characteristics of the mantle, and interrelated irreversible changes in the atmosphere and hydrosphere. The interdependence of the exogenic and endogenic carbon cycles determined by the exhalation of volcanic CO2 are discussed. The effect of periodic changes of climate and environment on the biosphere is illustrated using the example of Lake Baikal and the organisms inhabiting it. Periodic fluctuations in the composition of diatoms recorded in the sediments of Lake Baikal depend on fluctuations of temperature and aridity (dust storms). Phylogenetic trees of oligochaetes, mollusks, and colloid fish of Baikal reconstructed on the basis of frequency of substitution of nucleolide pairs (molecular clock) show a close correlation between the appearance of new species of oligochaetes and mollusks and the period of the first cooling (3.2-2.6 Ma), while the later speciation in fishes was also determined by other factors (e.g., development of mountains and changes in river drainage). Variations in the climatic system represent the superimposition of many fluctuations of different frequencies: those determined by geologic factors (millions of years), orbital cycles of Milankovitch (20-100 thousand years), inertia of the oceanic hydrosphere-atmosphere system (10 thousand years), and the superimposition of short-period variations differing in nature. Periods of recurring glaciations from 1.2 Ga and warm anomalies recorded 0.72-0.6 and 0.2-0.06 Ga played an important role. The Earth's earlier evolution was marked by the important boundaries of 1.2-1.4, 2.0, and 3.8 Ga, which are discussed in light of the evolution of the protobacterial biosphere and possible panspermy and represent an important geologic and biological problem.