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The Influence of UV Radiation on Protistan Evolution



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    1. Ecosystem Science and Technology Branch MS 239-20, NASA Ames Research Center, Moffett Field, California 94035-1000 USA
      Corresponding Author: L. Rothschild—Telephone number: (650) 604-6525; FAX: (650) 604-1088; Email:
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    The author originally submitted this paper at the International Society of Evolutionary Protistology Meeting, August 2–8, 1998, Flagstaff, Arizona.

Corresponding Author: L. Rothschild—Telephone number: (650) 604-6525; FAX: (650) 604-1088; Email:


Utraviolet radiation has provided an evolutionary challenge to life on Earth. Recent increases in surficial ultraviolet B fluxes have focused attention on the role of UV radiation in protistan ecology, cancer, and DNA damage. Exploiting this new wealth of data, I examine the possibility that ultraviolet radiation may have played a significant role in the evolution of the first eukaryotes, that is, protists. Protists probably arose well before the formation of a significant ozone shield, and thus were probably subjected to substantial ultraviolet A, ultraviolet B, and ultraviolet C fluxes early in their evolution. Evolution consists of the generation of heritable variations and the subsequent selection of these variants. Ultraviolet radiation has played a role both as a mutagen and as a selective agent. In its role as a mutagen, it may have been crucial in the origin of sex and as a driver for molecular evolution. As a selective agent, its influence has been broad. Discussed in this paper are the influence of ultraviolet radiation on biogeography, photosynthesis, and desiccation resistance.

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