Carbon dioxide biosphere function

The structural molecules of the skeletons and shells of invertebrates, which function as physical defenses against predation, are important in marine environments, where they produce carbonate and silicate rocks. Deposition in anaerobic environments has also been the basis for the formation of the extensive deposits of gas and oil that now fuel modern industrial societies. Removal of carbon from the biosphere by organisms to produce carbonate rocks, coal, oil, and hydrocarbon gases has been responsible for the presence of oxygen in the atmosphere of the Earth. Reversal of this process by human consumption of fossil fuels has already produced a detectable increase in atmospheric carbon dioxide. 

Given that carbon dioxide is intrinsic to the functions of the biosphere (Section 2.4.2), changes in the atmospheric mixing ratio of CO2 will inevitably bring about changes in the fimctioning of ecosystems, both througji... 

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