ECO - Energy Flow [LESSON]
Energy Flow
Energy flows through an ecosystem, while matter cycles within it. To understand why this is the case let’s take a closer look at how different life processes drive the movement of energy and matter in ecosystems.
Energy enters an ecosystem when producers carry out photosynthesis, capturing energy from the sun and storing it as chemical potential energy. During this process, matter from the environment (in the form of CO2) is taken in and rearranged into organic molecules (sugars). These organic molecules can power the producers’ life processes via cellular respiration or they can be stored as biomass. Next, energy and matter move up the trophic levels of an ecosystem as producers are eaten by primary consumers, which are then eaten by secondary consumers, and so on. Some of the organic material eaten by consumers is used for cellular respiration, some is stored as biomass, and the rest is excreted as waste.
Watch the Energy Flow through Ecosystems video below to learn more about energy flow through the ecosystem.
Food Webs
A food web is a model of feeding relationships in an ecosystem. When an organism is eaten, the matter and energy stored in its tissues are transferred to the organism that eats it. The arrows in a food web represent this transfer. For example, the arrow pointing from the mouse to the coyote in the food web below shows that matter and energy are transferred to coyotes when they eat mice.
Energy Pyramid and 10% Rule
Large amounts of energy are lost from the ecosystem between one trophic level and the next level as energy flows from the primary producers through the various trophic levels of consumers and decomposers. The main reason for this loss is the second law of thermodynamics, which states that whenever energy is converted from one form to another, there is a tendency toward disorder (entropy) in the system. In biologic systems, this means a great deal of energy is lost as metabolic heat when the organisms from one trophic level are consumed by the next level.
Pyramid ecosystem modeling is used to show energy flow through the trophic levels. Pyramids of energy are always upright, since energy is lost at each trophic level; an ecosystem without sufficient primary productivity cannot be supported. All types of ecological pyramids are useful for characterizing ecosystem structure. However, in the study of energy flow through the ecosystem, pyramids of energy are the most consistent and representative models of ecosystem structure. Pyramids are also used to represent biomass and number of organisms at each trophic level since they decrease as you move up.
Click the button to reveal the different parts of the food chain in the Energy Flow activity below.
Click the button to reveal the answer in the Energy Flow II activity below.
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