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Fig. 3. Milestones in evolution. (A) Paleontological periods of the Precambrian
era. (B) Estimates of total earth biomass as a function of time. The graph is
only a qualitative representation because it is not possible to establish or
extrapolate precise levels of precambrian biomass from paleontological records
(Kelly and Adams, 1994;
Papagiannis, 1984;
DeLong et al., 1994;
Koch, 1998;
O'Callaghan and Conrad, 1992;
Reeve, 1992). BYA, billion
years ago; Ph indicates initiation of the major increase in photosynthesis by
cyanobacteria.
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