Carbon dioxide in Earth's atmosphere able to synthesize food directly from and water using energy from light. However, not all organisms that use light as a source of energy carry out photosynthesis, since "photoheterotrophs" use organic compounds, rather than , as a source of carbon. In plants, algae and cyanobacteria, photosynthesis releases oxygen. This is called "oxygenic photosynthesis". Although there are some differences between oxygenic photosynthesis in plants, algae, and cyanobacteria, the overall process is quite similar in these organisms. However, there are some types of bacteria that carry out anoxygenic photosynthesis, which consumes but does not release oxygen. Carbon dioxide is converted into sugars
Carbon dioxide to prevent oxidation, though it has the problem that it can dissolve into the wine, making a previously still wine slightly fizzy. For this reason, other gases such as nitrogen or argon are preferred for this process by professional wine makers. Carbon dioxide is often used to "stun" animals before slaughter. "Stunning" may be a misnomer, as the animals are not knocked out immediately and may suffer distress. It is one of the most commonly used compressed gases for pneumatic (pressurized gas) systems in portable pressure tools. Carbon dioxide is also used as an atmosphere for welding, although in the