flour beetles
Introduction The purpose of this study was to measure and compare energy flow through the food chain in a natural old-field and a planted old-field. In order to understand how energy flows through an ecosystem we must first know something about the structure of the system. The structure of an ecosystem can be described as the contribution, distribution, and diversity of species that make up the system (Richardson 2003). After we know what the ecosystem is primarily composed of we can begin to understand how it functions. Function can be described as energy flow, nutrient cycling, productivity, and development of the system (Richardson 2003). Structure and function are closely related but function of an ecosystem varies depending on the structure. Not all of the organisms in an ecosystem are of equal sociologic importance (Daubenmire 1968). For example, one dominant species of vegetation may attract more, or fewer, species of primary consumers. These dominant species could also have an effect on the total biomass of primary consumers which would directly affect function of the system. Also, consider differences in structure in a forest ecosystem and an aquatic ecosystem and how function differs between them and how it differs from an old-field ecosystem. The structure of an ecosystem directly affects how it will function. In ecological systems energy is transferred from organism to organism. Plants, or primary producers, capture light energy from the sun and transform it into energy as carbohydrates (Ricklefs 2001). When a plant is eaten by an herbivore it is rebuilt into the structure of the animal or insect. Some of it is oxidized in respiration, converted into potential energy, or dissipated as heat. Energy transfer from one organism to another is always less than 100 percent efficient because the predator must expend energy, which is dissipated by heat, to eat the prey. Also, the assimilation of ingested food is incomplete. This means that the total amount of energy decreases at each successive trophic level.