Understanding energy transfer in ecosystems using food webs
Below is a digital story created for 9th and 10th grade high school biology students.
Energy transfer is essential to life. It is important for students to understand that energy is neither created, nor destroyed. This means organisms must first obtain energy before use and once they use that energy it will be transferred or transformed into other types of energy.
In an ecosystem, energy enters as solar energy from the sun. Producers, or autotrophic organisms, couple the solar energy with CO2(g) to make sugars in photosynthesis. About 10% of all the energy stored within producers can be transferred to primary (1°) consumers, when the herbivores consume the producers. Secondary (2°) consumers, or omnivores, consume producers and 1° consumers. These omnivores can also obtain about 10% of the energy stored in producers. If they ingest a 1° consumer, only about 10% of the energy stored within the primary consumer may be passed on to the omnivore. Finally, tertiary (3°) consumers are carnivorous and will only consume other consumers (both 1° and 2°) for energy.
Each trophic level may only pass on about 10% of the energy that organism stores because the vast majority of the energy within the organism is used to do work. As the energy is used for work, it is transferred to heat energy which ultimately passes from the individual to the surroundings.
All of this information can be easily represented by food webs. This video made with photopeach can be used to introduce students to the concept of a food web.
Energy transfer is essential to life. It is important for students to understand that energy is neither created, nor destroyed. This means organisms must first obtain energy before use and once they use that energy it will be transferred or transformed into other types of energy.
In an ecosystem, energy enters as solar energy from the sun. Producers, or autotrophic organisms, couple the solar energy with CO2(g) to make sugars in photosynthesis. About 10% of all the energy stored within producers can be transferred to primary (1°) consumers, when the herbivores consume the producers. Secondary (2°) consumers, or omnivores, consume producers and 1° consumers. These omnivores can also obtain about 10% of the energy stored in producers. If they ingest a 1° consumer, only about 10% of the energy stored within the primary consumer may be passed on to the omnivore. Finally, tertiary (3°) consumers are carnivorous and will only consume other consumers (both 1° and 2°) for energy.
Each trophic level may only pass on about 10% of the energy that organism stores because the vast majority of the energy within the organism is used to do work. As the energy is used for work, it is transferred to heat energy which ultimately passes from the individual to the surroundings.
All of this information can be easily represented by food webs. This video made with photopeach can be used to introduce students to the concept of a food web.
Constructing Food Webs on PhotoPeach
References:
"Photopeach" February 10, 2012. photopeach.com
Photos from:
"Seaweed." April 6, 2012. Retrieved from http://3.bp.blogspot.com/-5DovQp7mZ_o/Tyi7P0PQ5MI/AAAAAAAAHBM/gmoZaXcnxNk/s1600/SEAWEED+IN+SEA.jpg
Retrieved from "Coral Reef." April 10, 2012. Retreived from http://www.nwf.org/~/media/Content/Maps%20Graphs%20and%20Charts/Plants/Healthy%20Coral%20Reef.ashx?w=300&h=253&as=1
"School of fish." April 6, 2012. Retrieved from http://www.sipadan.org/photos/underwater/sipadan/fish-group/fish-group_01.jpg
"Wolf." April 6, 2012. Retrieved from http://images.nationalgeographic.com/wpf/media-live/photos/000/005/cache/grey-wolf_565_600x450.jpg
"Healthy Eating." April 6, 2012. Retrieved from http://www.doesregenerect.com/wp-content/uploads/2011/08/healthy-eating-children.jpg
"Food Webs." April 6, 2012. Retrieved from http://upload.wikimedia.org/wikipedia/commons/thumb/b/b3/FoodWeb.jpg/280px-FoodWeb.jpg
"Beluga Whale Food Web." March 29, 2012. Retrieved from http://seagrant.uaf.edu/nosb/papers/2004/steller-pops.html