Figure 1. An aquatic environment food chain. click for copyright

What is an environment? (Answer: An environment is the surrounding area that an organism lives in, including the air, water, food and energy needed for that organism to survive.) Can you think of an example? (Possible answers: Mountains, tree forests, river valleys, snow and water environments, as well as hot and cold climate environments, such as tropical rain forests and tundra.) What do you think supports these environments or keeps them running? What fuels the animals and plants that live within the environments and ecosystems we just discussed? It's energy! Today we are going to learn about how energy moves through an environment or ecosystem and how this knowledge helps us build a better biodome.

Why did you eat your most recent meal? (Many will say they were hungry, or that they wanted something sweet or salty.) We know that we have to eat to provide ourselves with the raw materials that help us to move, grow and stay healthy. Our food gives us the energy we need to perform daily activities. Do you know of other sources of energy and for what they are used? For example, fossil fuels (oil and coal) and renewable energy (solar or wind) are used for transportation, heating, cooling and electricity. Did you know that energy actually flows around in a system? For example, the energy in fossil fuels is changed into the heat or power that we need to run appliances or heat our homes — that energy moves from one form to another. It is the same with the food we eat; our bodies take the energy from the food and turn it into energy to move and grow. Many engineers study how energy moves through systems. Have you seen the latest running shoes for athletes? Engineers design new running shoes by looking at how energy moves from a person's legs to the ground upon which they are running. Environmental engineers study how energy moves through an ecosystem.

Have you heard of a food chain? A food chain traces the energy of nutrients through the organisms that eat them (see Figure 1). This includes the production of the vegetables, fruit, cheese, eggs or meat that you had for breakfast or will have for lunch or dinner. Energy is in all this food! From where does the energy in food come? Well, all the energy in food starts with the sun! Let's see if we can draw an example of this. (Write one or more of the example food chains in Figure 2 on the classroom board or overhead projector.)

Figure 2. Example food chains. click for copyright

The arrows in these food chains illustrate the direction of energy flow — starting with the sun providing nutrients to producers, which use photosynthesis to become food for consumers. What are producers and consumers? A producer is any organism that is capable of making its own food, usually through photosynthesis, such as a plant. A consumer is any organism that gets its food by eating producers or other organisms. What I just drew on the board are examples of simple food chains that show how energy moves from one place to another. A food web is what happens when one organism gets energy from more than one source, such as a human eating vegetables, ham and cheese.

How do we use the energy that is in the food we eat? We need energy to move, keep warm (we give off heat all the time, and this heat energy comes from the food we eat) grow, think, stay healthy and stay alive! Any energy that is left is stored in our bodies. Only a fraction of the energy that an herbivore, or plant eater, gets from the plant food that it eats becomes part of its body (its mass). The rest of the energy from the plant food is lost as waste (in droppings) or is used up (for movement, keeping warm or just surviving). The same goes for carnivores, or meat eaters, and omnivores, organisms that eat both meat and plants. When a carnivore or omnivore eats another animal, only a fraction of the energy from its animal food is incorporated into its body. Energy is lost at each link in the food chain because the living things pass on much less energy than they receive. This energy loss means that most food chains are only four or five links long. Discarded plant and animal (organic) materials eventually decompose, returning energy, in the form of nutrients, to the soil.

Figure 3. Elements of the hydrologic (water) cycle. click for copyright

The food chain alone is not responsible for the survival of plants and animals, humans. It is important to recognize that other nutrients, such as carbon, nitrogen, oxygen and water, also play a part in maintaining the ecosystems in which the living organisms of the world depend. How could we survive without water or air? Just as energy flows through organisms and the environment, these other nutrients also flow through the biosphere in cycles. For example, part of the water cycle includes water evaporating from rivers and oceans into the atmosphere where it builds up in clouds (condensation) and returns to the ground as rain or snow (precipitation) (see Figure 3).

Energy flow is something that engineers consider when designing systems and technologies. Whether they are dealing with existing technologies in our buildings, or new, cool mp3 players, or new technologies to help developing communities, or new fuels to power all of the things we use and rely upon every day, how energy flows is important to engineers. Similarly, all things in nature rely on a flow of energy to sustain themselves; plants and animals are all part of a network of energy flow. In addition, different weather and climates happen as a result of how energy flows through the biosphere. Weather systems are of particular interest to engineers who design sensors, measurement devices and meteorological computer models that help us predict weather patterns and inform weather forecasting.

(Optional: Show students the attached PowerPoint presentation, Energy Cycles Visual Aids, containing food chain, water cycle, carbon cycle and nitrogen cycle images.)

Today, let's think about how we might get energy, and other nutrients, such as water, carbon, nitrogen, and oxygen, into our biodomes for organisms to survive. Will we have any food chains in our biodomes? Any ideas?

What did we learn today? We learned that everything in the biosphere is connected by energy and nutrients in a web of cycles. We also learned how important the flow of energy and nutrients are through the biosphere to help organisms move, grow and survive. We learned that food chains and food webs show the flow of energy, where sunlight is converted to food for producers by photosynthesis, which then becomes food for consumers. Some of these consumers are food for still other consumers and so on. Can you give an example of a simple food chain for us? (Have a few students describe example food chains.) What is a producer? (Answer: A producer is any organism that is capable of making its own food, usually through photosynthesis, such as a plant.) What is a consumer? (Answer: A consumer is any organism that gets its food by eating producers or other organisms.) Why do engineers study the flow of energy through the biosphere? (Answer: Engineers need to understand how energy flows through a system in order to design technologies such as heating for buildings, new electronic devices, new technologies to help developing communities, or new fuels to power all of the things we use and rely upon daily.)

Pre-Lesson Assessment

Post-Introduction Assessment

Lesson Summary Assessment

See the water cycle in action with this animated diagram by the City of Lincoln, Nebraska: http://www.lincoln.ne.gov/city/pworks/water/funfacts/wtrcycle.htm (click to start animation).

See the nitrogen cycle in action with this animation on the Olympic National Park (WA) website: http://www.nps.gov/archive/olym/hand/process/ncycle.htm.