ENERGY AND ECOSYSTEMS

The survival of any organism in an ecosystem depends on the flow of energy and matter through its body. The ecosystem as a whole survives as a result of recycling matter and one-way flow of energy. The sun's energy directly or indirectly supplies the energy for almost all living things on earth. Producers use the sun's energy directly to make sugars and other energy-rich molecules. These materials are used directly or indirectly by the producers as sources of energy. Producers are a direct source of energy for some consumers; these consumers are then eaten by others. The decomposers within an ecosystem breakdown the wastes of living organism and breakdown the remains of those that die into useful nutrients for their own energy source and for the ecosystem as nutrients and minerals are recycled.

A food chain determines how energy and nutrients move from one organism to another in an ecosystem. Energy enters as sunlight>>>>>which is converted to nutrients by producers>>>>the energy is then passed on to consumers>>>>and eventually to decomposers. As each organism uses the chemical energy in its food to power life activities, much of the energy is converted into low-quality heat and flows into the environment. Producers belong to the first feeding level, primary consumers (herbivores--plant eaters) belong to the second feeding level, secondary consumers (carnivores--meat eaters) belong to the third feeding level and so on...

However, most ecosystems are more complex than a simple food chain. Most consumers feed on more than one type of organism and most organisms are eaten by more than one type of consumer. Since most organisms participate in many food chains, organisms in an ecosystem form a complex network of interconnected food chains called---food webs!