The period during which the presence of stromatolites decline is the Proterzoic period. Stromatolites are widely distributed sedimentary structures consisting of laminated carbonate or silicate rocks, produced over geologic time by the trapping, binding, or the precipitating of sediment by groups of microorganisms, primarily cyanobacteria.
2. The endosymbiotic theory suggests that a eukaryotic cell is the result of one prokaryotic cell eating another.
Hummingbirds can fly as fast as 60 miles per hour. One reason why its a scientific question is because of their speed. Their speed is very different compared to many other animals. I hope this helps :)
