school energy&environment

Energy transfer

The relations between the different components of an ecosystem are so close that, if one of them is damaged, the whole ecosystem is affected. The main relations are those established between energy flows and nutrient flows. The ecosystem is an open system as far as energy is concerned, that is energy continuously gets in and out of the system. The energy enters mainly from the sun, goes through and biotic community and its food chain, and goes out as heat, organic matter and resulting organisms. More into detail, the organisms produced are able to catch and use the solar energy in order to transform some inorganic compounds into organic compounds, through the photosynthesis. These compounds are used by producers in two ways: to live and to grow (the organic compounds form new structural elements of plant like leaves and new branches). Herbivores, by eating vegetables, absorb their organic substances and metabolise them, i.e. transform them into other organic substances that can be used for all vital functions (breathing, movements, body temperature, and many others) and use them as structural material in order to grow. Carnivore animals behave quite similarly, eating other animals. The process goes on in this way, from one category of organisms to another one. The transfer of energy through the food chain determines some heat to be lost into the environment, according to the second thermodynamics principle. This means that carnivores will have less energy, while eating, than herbivores, that in turn will receive from their food less energy than the amount used by plants when they metabolise their food (the organic matter that is formed thanks to the photosynthesis process). The energy transfer percentage for a trophic level to the next one is defined as “ecological efficiency” or efficiency of the food chain.