Might so-called Cambrium ‘explosion’ i.e. revelation, of animal phyla have been preceded (and required) by an increase in biomass? That is, for expansion of Animalia, isn’t expansion of food supply first required; same as for a species? How much do we know about prevalence of pre-Cambrium ‘plant’ species and abundance? Would any significant carbon associated with such strata (~550-70to+ myrs ago?) be consistent with the prevalence of biomass? But didn’t most all of our plant origin carbon based sedimentary layers come from Mezozoic; but becoming more prominant in earlier Silurian? Thus much reduced biomass in Paleozoic and Neo-proterozoic? But yet much earlier banded iron formation BIF was from 3.5-2.5 Byrs ago; reflecting oceanic photosynthesis, and oxygen biproduct, and extant biomass increase, initially from cyanobacteria. Would’t it be unlikely for nature to leave a new niche (increased food supply) unexplored for say 1 billion years? Were photosystem1 PSI, and more efficient energy generating photosystem 2, PSII, later arrivals? But photosynthesis, with chlorophyll light capture, charge seperation, and NADH reduction, occurs in cyanobacteria.
Sponge animals go back perhaps 700+ Myrs? Might Animalia be even deeper than this? When biological time rivals geological time, there is enough time for anything to happen.
What is an animal? Is Edicaran an animal? Whether it produces it’s own food might be a definition of paleo-phytoplankton i.e. ‘plant’. For example hydrothermal vent tube worms have bacteria on their surface, which supplies energy to tube worm; hence such tube worm is not a plant. So origin of Animalia requires an abundance of plant life (paleo-phytoplankton) opening up a new niche i.e. new life style.
Second Oxygenation would represent the result of such plant increased extant biomass; preceding, and setting the stage for arising of Animalia; rather than such oxygenation (i.e. increased energy generation) directly accounting for origin of Animalia?
Preceding Animalia, would require metazoa arising. In turn, might metazoa require an increase in free energy, such as aerobic metabolism rather than just anaerobic? Or might metazoans (faculative aerobes?) require just a lesser oxygenated envirns (ref 2)? Perhaps a small (few millimeter?) thin double walled slow metabolizing (facultative aerobe i.e. low oxygen tension?) hebivore?
Would it be easier to set limits on metazoa arising, rather than for origin of Animalia? Aerobic metabolism arose in single cell cyanobacteria. And mitochrondia-like single cell was incorporated into larger one cell organisms; with an organized nucleus? This occurred before metazoans. So might second oxygenation be reflective of not only increased biomass, but also required for additional aerobic metabolism such as tricarbocyclic acid cycle, which in turn might be required for metazoan arising, leading to the first heterotroph I.e. herbivore animalia; or just associated with (and required?) for more active carnivore niche?
Would such emphasis on extant biomass increase render an ecological model, in addition to any intrinsic aerobic metabolism advances, and any genetic or epigenetic developmental model, contributing to earlier metazoa and Animalia, and phyla development, eventually revealed at Cambrium stage? So might such first metazoan, and Animalia arising, be associated with Second Oxygenation Event, or with still much earlier times?
also see March 17, 2014 zankaon vignette.
Croce R. Photosystem I, Nature vol 348 6238, May 29, 2015.
Earth and Planetary Science Letters, June 2013, Vol.371:143–155, doi:10.1016/j.epsl.2013.04.003. A basin redox transect at the dawn of animal life. Erik A. Sperling, Galen P. Halverson, Andrew H. Knoll, Francis A. Macdonald, David T. Johnston
Andrew H. Knoll and Erik A. Sperling, Oxygen and animals in early earth history PNAS 2014 111 (11) 3907-3908; published ahead of print March 10, 2014, doi:10.1073/pnas.1401745111.
Oxygen requirements of early animals, PNAS March 18, 2014, Daniel B. Mills, Lewis M. Ward et al