Use Concept Maps to Teach the Transfer of Energy
Practical tips, lessons, and ideas for teaching the transfer of energy.
By Bruce Howard
Food webs and ecosystems are great middle school topics because they are intuitive, visual, and ripe for all kinds of hands-on and multimedia activities to illustrate the underlying concepts. Because they are so universally understood, these topics make a great jumping-off point to come back and reinforce or further develop certain big ideas, such as energy. Understanding where energy comes from, how it is transferred, and how it is used is foundational to a deep understanding of science, engineering, and technology.
A quick look on the Internet for lessons related to the transfer of energy through the ecosystem yields surprisingly few resources and ideas. There are many lessons on food webs and ecosystems, but few that emphasize the transfer of energy. The lessons I've chosen below are some of the best.
Objective
The objective is for my students to demonstrate how all living things rely on the process of photosynthesis to obtain energy.
Before approaching this topic, learners should already have a foundation. They should be able to demonstrate that plants require light energy to grow and survive, and understand different ways that organisms meet their energy needs. When they are done with the present topic, they should be able to distinguish between the basic features of photosynthesis and respiration.
Looking Deeper
So let's take a look at the flow of energy and how to teach it for deep understanding. Almost all of the energy found in a biological community can be traced back to plants. A biological community includes all of the living components of an ecosystem:
- Animals require air, water, a source of energy, and materials for growth and repair; plants have the same requirements but use light as their source of energy.
- Light is a form of energy. The sun is the major source of light energy used by plants.
- Chlorophyll is the substance found in the chloroplasts of a plant cell that reacts to light.
- Plants are producers whose cells capture light energy to make sugar molecules from atoms of carbon dioxide and water.
- Sugar molecules can be used as a direct energy source for the cell, incorporated into cell structures as a plant grows, or converted into starch and stored in vacuoles.
Through food webs, these molecules serve as sources of energy for the plants themselves and ultimately for all animals and decomposers. Less energy is available at successive levels of a food web because some is lost to the environment as heat during cellular respiration.
Concept Maps
A simple way to teach this idea of energy transfer is a three-step concept mapping activity. Begin by having pupils fill in the following table. (Answers in italics)
|
|
Energy Source(s) |
Needs for Growth |
Outputs |
|
Plants |
Sunlight |
Carbon Dioxide, Water |
Oxygen, Sugars, Fruits, Seeds, Carbonaceous Waste |
|
Animals |
Plant Sugars, Other Animals |
Various: Oxygen, Water, Other Animals, Vitamins, Minerals |
Carbon Dioxide, Waste, Protein & other nutrients (flesh), Decomposing matter |
Next, have them draw a concept map from the table. The nouns are the nodes and labels for arrows. They draw their placement with labeled arrows coming in and going out of the nodes. There are multiple ways to draw correct concept maps.
Last, have them use a red or orange colored pencil to draw dotted-line arrows and any additional nodes to show how energy moves from the sun to plants, plants to animals, animals and plants to waste, animals to animals, waste to insects.
Recommended Lessons:
The Down and Dirty Science videos provide pupils with an alternative view of how energy gets transferred through the ecosystem. After viewing the Down and Dirty Science videos, they will have a better concept of the complexity of the food web.
What path does this energy follow, and how is it transferred from one type of organism to another? In this feature, adapted from Interactive NOVA: "Earth," learn why 400 pounds of corn can't be converted into a 400-pound cow.
A lab where pupils learn a simple technique for quantifying the amount of photosynthesis that occurs in a given period of time, using a common water plant (Elodea). They use this technique to compare the amounts of photosynthesis that occur under conditions of low and high light levels.
If you use this lesson, you will want to emphasize how organisms in a temperate forest are dependent on one another for proper nutrition.
Here, your class will create a model of energy transfer using Microsoft Excel charts.
There are some good ideas here. Learners are introduced to food web via video. Then they conduct a series of activities which center on tracing energy flow, the nitrogen cycle, the carbon cycle, and understanding the role of photosynthesis and respiration.