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 Picnic'." This sampling was also praised by Fred DeUar of "High Fidelity News and Record Review", who stated it was done "in the cause of better-class '90s pop." "Billboard" called the track "a languid, liquid sketch of a lazy city afternoon" and stated "it gets the nod as [the album's] likeliest knockout contender." Ron Wynn from AllMusic declared "What I Need" one of the album's best. "Billboard" Larry Flick labelled it a "floor-filler" and an "upbeat rouser." Another reviewer from the same publication thought "What I Need" was one of the hits to be had from "Storyteller". "Vibe" magazine stated