Photosynthesis have formed symbiotic relationships with photosynthetic algae. These are most common in corals, sponges and sea anemones. It is presumed that this is due to the particularly simple body plans and large surface areas of these animals compared to their volumes. In addition, a few marine mollusks "Elysia viridis" and "Elysia chlorotica" also maintain a symbiotic relationship with chloroplasts they capture from the algae in their diet and then store in their bodies. This allows the mollusks to survive solely by photosynthesis for several months at a time. Some of the genes from the plant cell nucleus have even been
Fractionation of carbon isotopes in oxygenic photosynthesis processes that selectively use one carbon isotope over the other, or "fractionate" carbon through kinetic or thermodynamic effects. Oxygenic photosynthesis takes place in plants and microorganisms through different chemical pathways, so various forms of organic material reflect different ratios of C isotopes. Understanding these variations in carbon fractionation across species is applied in isotope geochemistry and ecological isotope studies to understand biochemical processes, establish food chains, or model the carbon cycle through geological time. Carbon isotope fractionations are expressed in using delta notation of "δ"C ("delta thirteen C"), which is reported in parts per thousand (per mille, ‰). "δ"C is