title: Ultraviolet selection pressure on the earliest organisms.
mesh_terms: D000447:Aldehydes; D005075:Biological Evolution; D002374:Catalase; D006862:Hydrogen Sulfide; D008025:Ligases; D008967:Molecular Biology; D010544:Peroxidases; D010777:Photochemistry; D011687:Purines; D011743:Pyrimidines; D014466:Ultraviolet Rays
chemical_list: D000447:Aldehydes; D011687:Purines; D011743:Pyrimidines; D010544:Peroxidases; D002374:Catalase; D008025:Ligases; D006862:Hydrogen Sulfide