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
Liquid latex The fumes from the ammonia in liquid latex can irritate the eyes when used as special effect make up on the face. For this reason it is recommended that liquid latex be allowed to vent for several minutes before being applied in this way. Appropriate liquid latex safety guidelines should be followed before the cosmetic use of liquid latex. Latex is a natural ingredient that comes from rubber trees in the form of a milky liquid. There are thousands of species of plants that produce different types of latex, including the Chicle tree that yields the raw material for producing