Photosynthesis More recent studies, reported in March 2018, also suggest that photosynthesis may have begun about 3.4 billion years ago. The main source of oxygen in the Earth's atmosphere derives from oxygenic photosynthesis, and its first appearance is sometimes referred to as the oxygen catastrophe. Geological evidence suggests that oxygenic photosynthesis, such as that in cyanobacteria, became important during the Paleoproterozoic era around 2 billion years ago. Modern photosynthesis in plants and most photosynthetic prokaryotes is oxygenic. Oxygenic photosynthesis uses water as an electron donor, which is oxidized to molecular oxygen () in the photosynthetic reaction center. Several groups of animals
What More Do I Need? What More Do I Need? "What More Do I Need?" is the 94th episode of the ABC television series, "Desperate Housewives". It is the seventh episode of the show's fifth season and aired on November 9, 2008. The story continues from the previous episode, when Lynette confronted Tom after she thought he is having an affair. They both misunderstood each other, but the situation is immediately resolved when Lynette realizes that Porter is the one who is having sex with Anne. Lynette and Tom ask Porter to end the relationship via the phone, but Porter refuses, fearing that Mr. Schilling