Energy Flow in the Pond Teacher s Guide February 2011 Grades: 6, 7 & 8 Time: 3 hours With the pond as a model, students explore how energy that originates from the sun keeps changing shape and form as it moves through an aquatic ecosystem. Wisconsin Standards: Students describe the flow of energy in natural systems, using the laws of thermodynamics and citing the sun as the source of energy for the earth. They use scientific equipment to collect data relevant to questions and investigations. They use data collected to develop explanations, make predictions and revise their understanding. Focus Concept: Energy flows through a pond ecosystem via food webs. Essential Understandings, Processes, and Skills: Understandings: 1. The sun is the primary source of all energy on earth. 2. All organisms need energy to survive and thrive. 3. The amount of energy available in a pond ecosystem is a limiting factor. 4. The amount of energy in a pond ecosystem determines the population it can support. 5. A pond food chain is made up of producers and consumers. A food chain describes the sequence of who eats or decomposes whom and determines how energy moves from one organism to another through the ecosystem. Food webs are made up of food chains. 6. Energy exists in many forms in a pond system. 7. Energy moves through an ecosystem with seasonal changes. 8. The first and second laws of thermodynamics govern the activities of all living things. Processes and Skills: 1. Collect and observe living organisms that are part of a pond system 2. Identify pond organisms using a taxonomic key 3. Use a microscope to observe pond organisms 4. Use books and adults to determine the trophic level of pond organisms 5. Develop conclusions based on collected data about energy flow in a pond 6. Predict the results of changes in the amount of energy available in the pond 1
Background: Organisms can be either producers or consumers in terms of energy flow through an ecosystem. 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 sunlight and use it to convert carbon dioxide into glucose (or other sugars). Algae and cyanobacteria are also photosynthetic producers, like plants. Consumers get their energy from the carbon bonds made by the producers. Based on what they eat, we can distinguish between 4 types of heterotrophs: herbivores, carnivores, omnivores, and detritivores. Energy and inorganic nutrients flow through the ecosystem as shown in this diagram. Energy "flows" through the ecosystem in the form of carbon-carbon bonds. When respiration occurs, the carbon-carbon bonds are broken and the carbon is combined with oxygen to form carbon dioxide. This process releases the energy, which is either used by the organism (to move its muscles, digest food, excrete wastes, think, etc.) or the energy may be lost as heat. The dark arrows represent the movement of this energy. Note that all energy comes from the sun, and that the ultimate fate of all energy in ecosystems is to be lost as heat. Energy does not recycle!! The other component shown in the diagram is the inorganic nutrients. They are inorganic because they do not contain carbon-carbon bonds. These inorganic nutrients include the phosphorous in your teeth, bones, and cellular membranes; the nitrogen in your amino acids (the building blocks of protein); and the iron in your blood (to name just a few of the inorganic nutrients). The open arrows represent the movement of the inorganic nutrients. Note that the producers obtain these inorganic nutrients from the inorganic nutrient pool, which is usually the soil or water surrounding the plants or algae. These inorganic nutrients are passed from organism to organism as one organism is consumed by another. Ultimately, all organisms die and become detritus, food for the decomposers. At this stage, the last of the energy is extracted (and lost as heat) and the inorganic nutrients are returned to the soil or water to be taken up again. The inorganic nutrients are recycled; the energy is not. Preparation Activities at School: Riveredge is a partner with you, the teacher, in creating a high-quality educational experience. We depend on you to prepare your students for the inquiry activities they will be doing at Riveredge. Please be sure to cover the following material with your students before your field trip; italicized items are most directly connected to our program. This preparation is essential to meet curriculum goals. We are committed to excellence so if you are unable to meet the minimum expectations of this guide, please contact a Riveredge educator for help at 262-675- 6888(local) or 262-375-2715(metro). Pre-fieldtrip Activities: Familiarize your students with the vocabulary words defined at the end of this guide. Prior to the field trip each student needs to have a working knowledge of energy. At the Center we will explore energy flow in living systems. To do this adequately, the students should be able to answer the following questions: What is energy? What is the major source of all energy? What are the different forms of energy? How is energy acquired and used by living organisms? Students should know how to use the attached "Key to Life in the Pond" identification key. 2
At Riveredge: Please meet your Riveredge teacher/naturalists in the main parking lot. Large classes may be divided into smaller groups, each with their own teacher/naturalist. This is best done upon arrival at Riveredge when the number of students and teacher/naturalists has been finalized. All necessary equipment will be provided by the center. We will be outside most of the day, rain or shine! Older shoes and clothing are highly recommended. Boots can be worn if rain is expected. Riveredge will supply rain ponchos if necessary. Sunglasses, cap with visor, sunblock, and long pants and sleeves will avoid sunburn. It is the responsibility of the student to supply these things for themselves. Please check the weather forecast and plan accordingly. A small water bottle may be carried on the trail if desired. 3
Students will examine the energy flow through a pond ecosystem through a study of pond plants and animals. Upon discerning the connections between pond organisms and their energy (food) source, students will realize that the amount of energy available in a given ecosystem determines who, what and how many organisms can live in that system. Follow-up Activities at School: For further study of energy we suggest you select activities from the following list. These ideas are only briefly discussed and should be expanded or adapted to fit your particular teaching situations. 1. Survey a field or other community for animal life and construct an energy pyramid. Discuss how this compares to the pond pyramid at the Center. 2. Research the history of fossil fuel use. Make a poster for the bulletin board showing the uses of conventional fuels in projected future consumption. Take this a step further with research into the history of pollution as it relates to energy use. Make a pollution overlay for the energy use poster. Discuss the impact of pollution on human environmental health. Gather information on human population by nation and compare their per capita calorie use and fossil fuel use. 3. Investigate renewable energy sources, i.e. wind, water and solar power. 4. Plant Explorations. Students should devise ways to experiment with plants to determine the importance of photosynthesis and the strategy plants have for increasing their photosynthetic abilities. For example, students might observe how plants turn their leaves toward the sun by turning a plant every three or four days, or cover one leaf of a plant with foil to see what happens to that leaf, or discuss why there is such a variety of leaf shapes and sizes in the plant kingdom. 5. Counting Calories. Use a calorie chart to compare the caloric (energy) values of various foods. Find each student's recommended number of calories needed daily. Discuss individual differences in metabolizing calories. Make a chart showing the caloric output during various kinds of exercise or activities. Compare each student's caloric intake with his/her caloric output on a daily basis. Discuss calorie storage (potential energy). When this energy is used through exercise and other activities what is it called? Kinetic energy -- movement and heat! Vocabulary: biomass The total dry weight of all organic matter in plants and animals in an ecosystem. caloric (chemical) energy The amount of energy supplied by food. carnivore An animal that eats other animals. community All the plants and animals that live together and interact with each other. decomposer An animal or fungus that gets its energy from dead plants or animals. ecosystem All of the living and nonliving things that interact together in an area. energy The ability to do work or to produce change. food chain The system in which living things eat or are eaten by other living things. food web A complex feeding system comprised of linked food chains in a particular ecosystem. herbivore An animal that eats plants. kinetic energy The energy produced by mass in motion. mechanical energy Energy produced by humans for their own use by harnessing energy in a natural system. omnivore An animal which eats both plants and other animals. photosynthesis The process in which green plants use sunlight, carbon dioxide, and water to make sugar and oxygen. potential energy Energy stored in a substance or a body. producer An organism that makes its food through the process of photosynthesis, usually a green plant. trophic level A stage in a food web occupied by organisms that feed on the same general type of food, used to diagram the energy flow within an ecosystem. Producers (green plants) are on the first trophic level, herbivores are on the second trophic level, and carnivores are on the third trophic level. 4
Energy Flow in the Pond Additional Resources: Websites: Energy and the Environment Wisconsin s Focus on Energy Program has background and resource information on many renewable energy technologies. www.focusonenergy.com Environmental Biology - Ecosystems This web page discusses how energy moves through an ecosystem. http://www.marietta.edu/~biol/102/ecosystem.html Energy Through Our Lives Unit Wisconsin K-12 Energy Education Program (KEEP) Activity Guide and website. The website covers the basics of energy in ecosystems and human society. https://www.uwsp.edu/cnr/wcee/keep/mod1/syllabus.htm Books: Energy and Ecology, David M. Gates, Sinauer Associates, Inc., 1985. 5