In most cases, energy in an ecosystem begins with the sun. Certain types of organisms-including plants and some members of the Bacteria, Archaea, and Protoctista kingdoms-are called producers because they can make their own food from abiotic components in the environment. The ingredients of photosynthesis are carbon dioxde, water, and sunlight. Carbon dioxide is a gas found in the atmosphere and in water. Plants obtain co2 through small holes in their leaves. Water is drawn in through their roots. Among less complex producers these substances diffuse into the body through the surrounding cell membrane.