Energy Flow: Through Food Chains and Food Webs

1. Energy Flow: Through Food Chains and Food Webs Shawn McLeod

2. Food Chain A food chain is an illustration of how energy and matter travel through an ecosystem. The food chain starts with a producer, the flower. The flower is eaten by the caterpillar, which is called the primary consumer. The caterpillar gets matter and energy from the flower. The caterpillar is eaten by the frog. The frog is called the secondary consumer and gets matter and energy from the caterpillar. The snake is the tertiary or third consumer because it eats the frog and gets matter and energy from it. Finally the owl eats the snake and is called the quaternary or fourth consumer.

3. How Energy and matter is Passed Around: • Energy and matter is passed from one level (called trophic levels) of the food chain to the next. It takes the shape of a pyramid because there are more producers than primary consumers, more primary consumers than secondary consumers, and so on.

4. Energy Pyramid • Each level of the pyramid is called a trophic level. • As energy travels up the energy pyramid through each trophic level, most of it is lost in the form of heat. Since most of the energy is lost or used, less energy is available to the organisms at each level going up the pyramid.

5. Sources of Energy • The ultimate source of energy on the Earth is from the Sun. • Autotrophs (Producers) use the Sun to make their own food through photosynthesis. • Herbivores (Primary Consumers) eat the producers for energy. • Carnivores (Secondary Consumers) eat the Primary Consumers.

6. Sources of Energy • Then there are Omnivores, who are capable of eating both the Herbivores and the Carnivores.   • All organisms, Producers and Consumers give off waste products that are consumed by the Detrivores (Decomposers). The Decomposers provide nutrients that the producers can use along with the sun to photosynthesize.

7. Food Webs • If you put all this stuff together you get a food web  • A food web better represents a real life community than a food chain, it involves several food chains that are inter-linked. Many preditors prey upon more than one prey item, and many organisms are preyed upon by more than one preditor.

8. Food Webs • A food web is a complex illustration showing the relationship of how matter and energy flows through an ecosystem • A food web is composed of many different food chains combined.

9. All organisms contribute to the flow of energy in the ecosystem. Without one of the organisms an entire ecosystem can collapse. The relationship between all of the organisms is essential.

10. Video

11. Your Assignment • Choose your favorite biome • Make three food chains • Combine the three food chains to make a food web • Turn the verbal food web into a pictorial food web.

12. Web Links and Resources • http://www.absc.usgs.gov/research/seabird_foragefish/marinehabitat/home.html • http://www.ecokids.ca/pub/eco_info/topics/frogs/chain_reaction/index.cfm • Miller, Kenneth and Levine, Joseph. Biology. prentice hall, 2006. • Postlethwait, John and Hopson, Janet. Modern Biology. Holt, Rinhart and Winston, 2006