Here's how they do it:

* Photosynthesis: Plants and algae use sunlight, water, and carbon dioxide to create their own food (sugars) through a process called photosynthesis. This process releases oxygen as a byproduct.

Other organisms that contribute to oxygen production:

* Cyanobacteria: These microscopic organisms are also photosynthetic and are thought to have played a major role in oxygenating the Earth's atmosphere billions of years ago.

* Phytoplankton: These tiny marine algae are responsible for a significant portion of the world's oxygen production.

In summary: While other organisms may contribute to oxygen production in smaller amounts, plants and algae are the main oxygen producers on Earth.