Tuesday, October 1, 2019

Atmospheric Oxygen, Giant Paleozoic Insects and the Evolution of Aeria

Animal gigantism was prevalent during the Carboniferous period of the Paleozoic era. Gigantism in flying insects occurred in abundance; however, arthropods, such as arthropleurids, also experienced gigantism. Arthropleurids existed during the Paleozoic era and were the largest land dwelling arthropods in the history of the Earth. 1m long millipedes are classified as arthropleurids. Amphibians such as the terrestrial labyrinthodont amphibians also became gigantic during the Carboniferous period. Large amphibians reached body lengths of up to 2m. However, these amphibians are limited by respiration through the skin, which is known to restrict maximum body size. The wingspan of a certain extinct dragon fly exceeded 70cm and the wingspan of late Paleozoic Paleodictyoptera was between .9-43cm. There are a few hypotheses that have been aimed at explaining the gigantism during the Paleozoic era. Some are predatory defense and enhanced flight performance. However, the most plausible is the idea that the oxygen increase in the atmosphere caused the increase in body size. Increased oxygen partial pressure caused an increase in diffusive flux in the tracheal system. This led to the adaptation of the bodies of insects, amphibians, and arthropods to the new environment. Carboniferous - is a major division of the geologic timescale that extends from the end of the Devonian period, about 359.2 Ma (million years ago), to the beginning of the Permian period, about 299.0 Ma (ICS 2004). Geological records of atmospheric oxygen and carbon dioxide Since plants have been able to survive on land by carbon dioxide fixation, also known as terrestrializaion, the earth’s atmosphere has undergone a ... ...f terrestrial arthropods with diffusion-limited respiratory systems is consistent with the levels of atmospheric oxygen. (This can be seen in the charts included in the article) A second peak of insect gigantism appears to occur in the Cretaceous period when the atmosphere was also hyperoxic, or contained a high concentration of oxygen. References Orr, W. C. and Sohal, R. S. (1994). Extension of life-span by overexpression of superoxide dismutase and catalase in Drosophila melanogaster. Science 263, 1128–1130. Tyler, R. H., Brar, H., Singh, M., Latorre, A., Graves, J. L., Mueller, L. D., Rose, M. R. and Ayala, F. J. (1993). The effect of superoxide dismutase alleles on aging in Drosophila. Genetica 91, 143–149. Withers, P.C. (1981). The effects of ambient air pressure on oxygen consumption of resting and hovering honeybees. J. comp. Physiol.

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