Here's why:
* Photosynthesis: These organisms use sunlight, carbon dioxide, and water to produce glucose (sugar) and oxygen. This process provides them with energy and building blocks for growth.
* Cellular Respiration: These organisms break down the glucose they produced through photosynthesis to release energy (ATP) for their cellular functions. This process requires oxygen and releases carbon dioxide as a byproduct.
Therefore, these organisms are autotrophs, meaning they can produce their own food through photosynthesis, and they also use cellular respiration to extract energy from that food. This cycle allows them to sustain themselves and contribute to the balance of the Earth's ecosystem.
