In an ecosystem, primary producers create their own food sources. These producers can vary from one ecosystem type to another. In a forest ecosystem, the primary producers are plants that create their own food via photosynthesis, while in the ocean organisms like phytoplankton produce their own energy and provide oxygen to the ocean aquatic life.
Producers can range in size from large plants like trees to much smaller organisms like plankton. Some types of plankton or algae are so small they can be difficult to see with the human eye. Producers create their own food using the sun's rays in a process called photosynthesis.
The energy gained from the sun's rays is paired with carbon dioxide taken from the air and water from the soil to produce the sugars that are needed to keep the plant healthy and alive. In turn, these organisms create oxygen for the other organisms in their ecosystem.
These organisms are generally consumers or in some cases decomposers. The consumers eat not only the producers, but in some cases, they eat other consumers as well. The cycle of producers, to consumers and decomposers is required for the cycle of life. If one of these groups or steps disappeared from the ecosystem, it would affect the next cycle and effectively disrupt or destroy the ecosystem.