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
Ghetto Day/What I Need "What I Need" and "100% Pure Love", the album's first single, "ooze with giddy abandon—not to mention juicy grooves that seep deeper into the brain and body upon repeated spins." "What I Need" was claimed by "Spin" Bernstein to have "xeroxed" Clivillés and Cole's 1991 single "A Deeper Love". However, he predicted that it could have been a potential successor to her previous signature hits, "Gypsy Woman" and "Makin' Happy". "Ghetto Day" and "What I Need" were released as a double A-side single in June 1994. The joint release peaked at 40 on the UK Singles Chart and at No.