Food
Living creatures require a carbon and energy source to conduct life processes. This carbon and energy comes from food. Animals and many other creatures acquire this carbon and energy through the substances they eat. This food is digested and the molecules are broken down through cellular processes that occur in the cytoplasm and mitochondria of the animal cell. Plants break down food much the same way as animals. However, plants are able to produce their food through photosynthetic processes.
Photosynthetic Pigments
Photosynthesis requires the use of specialized pigments such as chlorophylls, carotenoids and phycobiliins to use sunlight to produce energy. These pigments absorb specific wavelengths of light. Wavelengths reflected by the pigment give the pigment its color. Chlorophyll, for example, appears green since it is reflecting the wavelengths of light associated with green while absorbing the other wavelengths. These pigments are arranged in the chloroplasts.
Photosynthesis - Light Dependent Processes
In the first stage of photosynthesis, referred to as the light dependent processes, the pigments allow sunlight to be coupled to enzymatic reactions that create high energy molecules such as ATP (adenosine triphophate). Oxygen is released in the course of these reactions.
Photosynthesis--Light Independent Processes
In the second stage of photosynthesis, carbon fixation occurs. The high energy molecules produced in the light dependent stage of photosynthesis are used to create organic compounds from carbon dioxide in a series of reactions collectively known as the Calvin-Benson Cycle. These organic compounds become the food for the plant. Since the plant is making its own food, it is referred to as an autotroph.
Producers in Ecology
Organisms that produce their own food also produce the food for other organisms. Consumers, such as animals, derive their carbon and energy directly or indirectly from the plants. The producer becomes the food for another organism that consumes the producer. An additional step in this chain can be added to consumers which consume other consumers. Consumers such as animals, derive their carbon and energy directly or indirectly from the plants.
Other Producers
While green plants are perhaps the most familiar producers in ecosystems, they are by no means the only producers. Photosynthesis also occurs in a number of prokaryotes and protists. Additionally, some organisms are able to utilize sunlight for an energy source but are unable to fix carbon. Lastly, hydrothermal vents on the seafloor use chemosynthetic bacteria as the producers for a complex ecosystem.
