What is the basic role of CO2 in photosynthesis
But the branch of the that readers might find most interesting led to humans. Humans are in the phylum, and the last common ancestor that founded the Chordata phylum is still a mystery and understandably a source of controversy. Was our ancestor a ? A ? Peter Ward made the case, as have others for a long time, that it was the sea squirt, also called a tunicate, which in its larval stage resembles a fish. The nerve cord in most bilaterally symmetric animals runs below the belly, not above it, and a sea squirt that never grew up may have been our direct ancestor. Adult tunicates are also highly adapted to extracting oxygen from water, even too much so, with only about 10% of today’s available oxygen extracted in tunicate respiration. It may mean that tunicates adapted to low oxygen conditions early on. Ward’s respiration hypothesis, which makes the case that adapting to low oxygen conditions was an evolutionary spur for animals, will repeatedly reappear in this essay, as will . Ward’s hypothesis may be proven wrong or will not have the key influence that he attributes to it, but it also has plenty going for it. The idea that fluctuating oxygen levels impacted animal evolution has been gaining support in recent years, particularly in light of recent reconstructions of oxygen levels in the eon of complex life, called and , which have yielded broadly similar results, but their variances mean that much more work needs to be performed before on the can be done, if it ever can be. Ward’s basic hypotheses is that when oxygen levels are high, ecosystems are diverse and life is an easy proposition; when oxygen levels are low, animals adapted to high oxygen levels go extinct and the survivors are adapted to low oxygen with body plan changes, and their adaptations helped them dominate after the extinctions. The has a pretty wide range of potential error, particularly in the early years, and it also tracked atmospheric carbon dioxide levels. The challenges to the validity of a model based on data with such a wide range of error are understandable. But some broad trends are unmistakable, as it is with other models, some of which are generally declining carbon dioxide levels, some huge oxygen spikes, and the generally relationship between oxygen and carbon dioxide levels, which a geochemist would expect. The high carbon dioxide level during the Cambrian, of at least 4,000 PPM (the "RCO2" in the below graphic is a ratio of the calculated CO2 levels to today's levels), is what scientists think made the times so hot. (Permission: Peter Ward, June 2014)
What is the basic role of CO 2 in photosynthesis
chloroplast | Function, Location, & Diagram | …
As oxygenic photosynthesis spread through the oceans, everything that could be oxidized by oxygen was, during what is called the (“GOE”), although there may have been multiple dramatic events. The event began as long as three bya and is . The ancient carbon cycle included volcanoes spewing a number of gases into the atmosphere, including hydrogen sulfide, sulfur dioxide, and hydrogen, but carbon dioxide was particularly important. When the continents began forming, carbon dioxide was removed from the atmosphere via water capturing it, , the carbon became combined into calcium carbonate, and plate tectonics subducted the calcium carbonate in the ocean sediments into the crust, which was again released as carbon dioxide in volcanoes.
Carbon Dioxide in the Ocean and Atmosphere - sea, …
In summary, today’s orthodox late-Proterozoic hypothesis is that the complex dynamics of a supercontinent breakup somehow triggered . The global glaciation was reversed by runaway effects primarily related to an immense increase in atmospheric carbon dioxide. During the events, oceanic life would have been delivered vast amounts of continental nutrients scoured from the rocks by glaciers, and the hot conditions would have combined to create a global explosion of photosynthetic life. A billion years of relative equilibrium between prokaryotes and eukaryotes was ultimately shattered, and oxygen levels began rising during the Cryogenian and Ediacaran periods toward modern levels. Largely sterilized oceans, which began to be oxygenated at depth for the first time, are now thought to have prepared the way for what came next: the rise of complex life.