title: Modeling Variable Phanerozoic Oxygen Effects on Physiology and Evolution.
abstract: Geochemical approximation of Earth's atmospheric O2 level over geologic time prompts hypotheses linking hyper- and hypoxic atmospheres to transformative events in the evolutionary history of the biosphere. Such correlations, however, remain problematic due to the relative imprecision of the timing and scope of oxygen change and the looseness of its overlay on the chronology of key biotic events such as radiations, evolutionary innovation, and extinctions. There are nevertheless general attributions of atmospheric oxygen concentration to key evolutionary changes among groups having a primary dependence upon oxygen diffusion for respiration. These include the occurrence of Devonian hypoxia and the accentuation of air-breathing dependence leading to the origin of vertebrate terrestriality, the occurrence of Carboniferous-Permian hyperoxia and the major radiation of early tetrapods and the origins of insect flight and gigantism, and the Mid-Late Permian oxygen decline accompanying the Permian extinction. However, because of variability between and error within different atmospheric models, there is little basis for postulating correlations outside the Late Paleozoic. Other problems arising in the correlation of paleo-oxygen with significant biological events include tendencies to ignore the role of blood pigment affinity modulation in maintaining homeostasis, the slow rates of O2 change that would have allowed for adaptation, and significant respiratory and circulatory modifications that can and do occur without changes in atmospheric oxygen. The purpose of this paper is thus to refocus thinking about basic questions central to the biological and physiological implications of O2 change over geological time.
authors.affiliation: Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA.|Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA.
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Graham
authors.affiliation: Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA.|Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA.|Department of Ecology and Evolution, University of California, Irvine, Irvine, CA, USA.
authors.forename: Corey J
authors.initials: CJ
authors.lastname: Jew
authors.affiliation: Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA. nick.wegner@noaa.gov.|Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA. nick.wegner@noaa.gov.|Fisheries Resources Division, Southwest Fisheries Science Center, NOAA Fisheries, La Jolla, CA, USA. nick.wegner@noaa.gov.
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Wegner
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005580:Fossils; D006801:Humans; D008954:Models, Biological; D010100:Oxygen / Q000494:pharmacology*; D010829:Physiological Phenomena / Q000187:drug effects*; D012119:Respiration
chemical_list: D010100:Oxygen
keywords: Evolution; Hyperoxia; Hypoxia; Oxygen; Paleoatmosphere; Paleozoic; Tetrapod