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Guide 1: Energy flows, Food Chains and Food Webs


Do you like to play games? If you do, you will need energy. Everytime you run or jump, you are using up energy in your body. How do you get the energy to play? You get energy from the food you eat. Similarly, all living things get energy from their food so thatthey can move and grow. As food passes through the body, some of it is digested. This process of digestion releases energy.

A food chain shows how each living thing gets its food. Some animals eatplants and some animals eat other animals. For example, a simple food chain links the trees and shrubs, the giraffes (that eat trees and shrubs), and the lions (that eat the giraffes). Each link in thischain is food for the next link. A food chain always starts with plant life and ends with an animal.

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Organisms can be either producers or consumers in terms of energy flow through anecosystem. Producers convert energy from the environment into carbon bonds, such as those found in the sugar glucose. Plants are the most obvious examples of producers; plants take energy from sunlightand use it to convert carbon dioxide into glucose (or other sugars). Algae and cyanobacteria are also photosynthetic producers, like plants. Other producers include bacteria living around deep-seavents. These bacteria take energy from chemicals coming from the Earth's interior and use it to make sugars. Other bacteria living deep underground can also produce sugars from such inorganic sources.Another word for producers is autotrophs.

Animals need a variety of nutrients to meet their basic needs. These nutrients include fats and carbohydrates that provide energy, proteins that furnishamino acids, vitamins that serve as co-factors for enzymes and perform other functions, ions required for water balance and for nerve and muscle function, and selected elements that are incorporated...