The type of photosynthesis that does not produce oxygen is called anoxygenic photosynthesis.

Here's why:

* Normal Photosynthesis (Oxygenic): Most plants, algae, and cyanobacteria use oxygenic photosynthesis. This process uses water as the electron donor, splitting it and releasing oxygen as a byproduct.

* Anoxygenic Photosynthesis: This type of photosynthesis uses other electron donors instead of water, such as hydrogen sulfide (H₂S), sulfur (S), or ferrous iron (Fe²⁺). Because they don't use water, they don't produce oxygen.

Key differences:

* Electron Donor: Oxygenic uses water, anoxygenic uses other compounds.

* Oxygen Production: Oxygenic produces oxygen, anoxygenic does not.

* Organisms: Oxygenic is common in plants, algae, and cyanobacteria. Anoxygenic is found in some bacteria, like purple bacteria and green sulfur bacteria.

Let me know if you have any more questions!