BIOGEOCHEMISTRY: ON PHOTOSYNTHESIS 3.4 BILLION YEARS AGO

BIOGEOCHEMISTRY: ON PHOTOSYNTHESIS 3.4 BILLION YEARS AGO: "Cyanobacteria exhibit oxygenic photosynthesis, but a number of photosynthetic bacteria (e.g., sulfur bacteria) are not oxygenic (nonoxygenic). In addition to the absence of oxygen production, nonoxygenic photosynthesis differs from oxygenic photosynthesis in two other ways: a) nonoxygenic photosynthesis involves absorption of light of longer wavelengths by pigments called bacteriochlorophylls; b) in nonoxygenic photosynthesis, reduced compounds other than water (e.g., hydrogen sulfide or organic molecules) provide the electrons needed for the reduction of carbon dioxide."