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Cold Climate Produced By Algae Contributed To Onset Of Multicellular Life
Los Angeles CA (SPX) Feb 15, 2007 The rise of multicellular animals about 540 million years ago was a turning point in the history of life. A group of Finnish scientists suggests a new climate-biosphere interaction mechanism for the underlying processes in a new study, which will be published on February 14, 2007 in PLoS ONE, the international, peer-reviewed, open-access, online publication from the Public Library of Science (PLoS). The theory invokes cold, ice-containing climates as a key precursor for multicellular life. If the model turns out to be correct, one can assume that complex life might exist also around stars which are more massive and short-lived than the Sun. Since remote sensing of highly reflecting glaciers should be possible, this may help designing future astronomical observation programmes for earthlike extrasolar planets. Multicellular life was preceded by the cold Neoproterozoic climate 600-800 million years ago which at times produced widespread glaciations. According to the new theory, the coldness was due to low carbon dioxide concentration brought about by strong algal growth in the oceans. The algal growth was maintained by the lack of grazing animals and the ability of cold seawater to mix and transport nutrients efficiently. A moderately high seawater oxygen concentration developed as a byproduct of the algal growth. This enabled diffusive breathing of primitive multicellulars which were larger than their unicellular counterparts. The ability of cold water to contain more dissolved oxygen also helped the multicellulars to thrive. The diversification of the marine food webs introduced by multicellular predators as well as the moving and burrowing activity of animals on the seafloor contributed to a more efficient decomposition of the algae-produced organic carbon, which slowed the rate of organic carbon sequestration. This in turn increased the atmospheric carbon dioxide level and ended the severe glaciations and the reign of unicellular algae, initiating the development of a modern-type climate. Citation: Janhunen P, Kaartokallio H, Oksanen I, Lehto K, Lehton H (2007) Biological Feedbacks as Cause and Demise of Neoproterozoic Icehouse: Astrobiological Prospects for Faster Evolution and Importance of Cold Conditions. PLoS ONE 2(2): Online Paper Related Links Explore The Early Earth at TerraDaily.com Explore The Early Earth at TerraDaily.com
Ancient Rocks Show How Earth May Have Dodged Frozen Fate Of Mars
Boulder CO (SPX) Feb 06, 2007Carbon dioxide, a greenhouse gas that has become a bane of modern society, may have saved Earth from freezing over early in the planet's history, according to the first detailed laboratory analysis of the world's oldest sedimentary rocks. Scientists have theorized for years that high concentrations of greenhouse gases could have helped Earth avoid global freezing in its youth by allowing the atmosphere to retain more heat than it lost. |
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