Independent Indicators of Phanerozoic O

The theoretical calculations of the evolution of atmospheric O2 over Phanerozoic time can be checked against geological observations. Because the metabolism of plants and animals are sensitive to levels of O2 in the environment, one can look at the paleontological and paleobo-tanical record for suggestions of possible changes in atmospheric O2 and limits on maximum and minimum O2 concentrations. To do this on a quantitative basis, experiments on the response of modern organisms to changes in O2 are necessary. Combining modern experiments with observations of physiologically dependent features of fossil organisms leads to the underexplored field of paleophysiology. (A pioneering and largely forgotten paper on this subject is that of McAlester, 1970.) In

Time my

Figure 6.8. Comparison of calculated values of atmospheric O2 over Phanerozoic time by RROD isotope mass balance modeling and the a-priori modeling of Bergman et al. (2003).

addition to paleophysiology, limits on O2 variation also can be made by studying experimentally the effect of O2 concentrations on fire behavior and comparing results with the evidence for paleofires, such as charcoal occurrences and the fire resistance of ancient plants.

Organic Gardening

Organic Gardening

Gardening is also a great way to provide healthy food for you and your loved ones. When you buy produce from the store, it just isnt the same as presenting a salad to your family that came exclusively from your garden worked by your own two hands.

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