Photosynthesis is the process through which an organism internally makes food by breaking down sunlight. Organisms that make food through photosynthesis are classified as "autotrophs," as opposed to "heterotrophs," which must consume other organisms to make their food. The kingdoms which contain photosynthetic organisms are Monera, Protista and Plantae.
Process of Photosynthesis
During photosynthesis, the energy from sunlight is broken down with carbon dioxide and water to form ATPs (adenosine triphosphate). ATPs are then used to power reactions in the cell that produce glucose, the primary sugar used to fuel the cell's activities. The light used in the reaction for photosynthesis is absorbed by chlorophyll, an organelle in the cell, that is able to take in red or blue light. Oxygen is a waste product of photosynthesis.
The Monera Kingdom (which is divided into two kingdoms, the Eubacteria and Archeobacteria) are microscopic, single-celled organisms that are the simplest known forms of life. Monera are bacteria, and while several of them absorb their food, many others have the capability to produce their own food through photosynthesis. Due to their simple single cell nature, some bacteria photosynthesize in a primitive manner. For example, halobacteria has no chlorophyll and does not process carbon dioxide as part of its process.
The Protista Kingdom lies between the Monera Kingdom and the Plantae Kingdom; most protists are still single-celled like bacteria, but their cells are more complex. Like bacteria, not all protists are autotrophic; however, almost all protists that do engage in photosynthesis have some type of chlorophyll. The most common type of photosynthetic protists are algae (though some algae are bacteria). Some protists, such as the Euglenophyta, will engage in photosynthesis when there is a light source, but will eat other organisms when there is no light.
All organisms in the Kingdom Plantae are multilcellular and autotrophic. According to the University of California at Berkeley, there are over 250,000 species of plants, which makes them the second largest kingdom behind Animalia. Due to their complex cells, plants have a specialized organelle in their cells that process photosynthesis, called the "chloroplast." A plant's chorophyll is contained in the chloroplast, which gives a plant its green color.