Green plants make their own food by the process of photosynthesis using sunlight. Most of the autotrophs use carbon dioxide, sunlight and carbon dioxide to produce glucose that is used by the plants to obtain energy. Most of the oxygen comes from these organisms and decrease in the number of green plants can lead to several problems due to decrease in the amount of oxygen. Example: green plants, algae, and even some bacteria. This food and oxygen is produced by the action of autotrophic organisms
