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Making Our Food on Earth, in Space and on Mars
Teacher's Notes
Most grade-one students are not strong readers, or perhaps not readers at all. The intent of this lesson is to get students familiar with the word energy and the word joule, and to emphasize that energy is a requirement of all living things.
Grade one students should get the "feeling" that the ability to utilize energy is a characteristic of all living things and that energy must be constantly supplied in order to keep living things alive.
If humans travel long distances, over a number of days, weeks, months or oven years, they will need to take food with them.
A round trip to the planet Mars will take several years!
The details of energy conversion are not important here. Focus on the concept that living things need energy, and that the primary source of that energy is the food we (and other living things) eat.
Things to Emphasize
Living things require energy;
Green plants get their energy from sunlight;
Green plants convert sunlight energy into food energy;
Other living things (such as humans) get their energy from the food that they consume;
All energy in food comes from the energy in sunlight;
Science investigation involves a multi-step inquiry process: ask an initial question, plan the investigation, record observations and collect data, analyze data to draw a conclusion, and communicate the findings.
Consider the Following
Everyday we have to eat something. If we don't eat our bodies complain; we begin to feel hungry. In fact, human activities are scheduled around meal times. The traditional meals are morning, midday, and evening.
Why is this?
In general there are three reasons for this:
The food we eat gives us energy. We need this energy to move, to grow, and even to let our brains think. All of these activities require energy.
The food we eat gives our bodies the raw materials we need to grow (the building blocks of our bones, our muscles, our hair and so on.)
Stopping our daily activities to eat gives our body and our brains a chance to rest briefly during the day.
This discussion raises the issue, how does energy get into the food we eat?
Astronauts need food
On a long trip, such as a mission to Mars, humans will (a) either carry all their food with them, (b) grow their food during the trip and on the surface of Mars, or (c) a combination of these two.
How Do Plants Make Food?
Green plants are the source of food energy. Green plants, and only green plants, have the unique ability to lock the energy of sunlight into the food we eat. The diagram shown below illustrates the process by which this happens. The raw materials are water, carbon dioxide and of course energy (from sunlight). In the simplest case, the food produced is sugar, the stuff that makes fruit and some vegetables taste sweet.
The diagram below shows conceptually how a plant makes food.
All food energy comes from the energy in sunlight. How does the energy get into the food we eat? It's all done by the magic of photosynthesis in the green leaves of plants.
Green plants act as food factories converting sunlight, water and carbon dioxide (found in the air) into food.
Planting potted plants, especially some vegetables, in your classroom is a good way to let students observe the process of plant growth. If the plants are allowed to mature, the produce can be eaten. You can explain to the students that they are, in some sense, 'eating sunshine', and that they are 'solar powered!'
Converting Sunlight in Food Energy
The image to the left illustrates the essential elements in the production of food. The elements are deliberately unlabelled so that students can visually identify each of them.
It should be pointed out that a major source of carbon dioxide in their classroom comes from their breath.
Each time students exhale (breathe out), they add carbon dioxide to the air around them.
Activities
Ask students to fold a sheet of construction paper in half and print the heading "Plants" on one half and "Animals" on the other. Have them cut out or draw pictures of foods they eat and place them in the corresponding columns.
Engage students in an investigation of the effect of sunlight on plant growth. Before beginning the investigation, ask students to suggest ways to investigate the effect of sunlight on plant growth. Give students opportunities to formulate questions, help plan the procedure and make predictions. Record their questions, procedure and hypotheses. Use two plants that are almost identical. Place one plant on a sunny window ledge and the other in a dark place such as a closet or filing cabinet. Explain the importance of treating the two plants identically except for the amount of sunlight. At the beginning and end of each week, observe the plants and discuss and have the students record the differences between them. (Note: if your class has access to a digital camera, pictures could become part of your observations).
Have students create a visual text to explain energy conversion.
Ask students to collect pictures of animals that eat plants.
Have students cut out the pictures from the Blackline Master and glue them together in a logical fashion on construction paper. Ask them to explain the conversion of energy in their picture.
Ask students to collect (with help from their parents) the nutrition panels from food packages. How much energy in joules (J) or kilojoules (kJ) is in each package or serving of the product? The idea here is to simply reinforce the concept that food contains energy and to become familiar with the words joule and kilojoule.
Ask students how animals which don't eat plants get their energy. (Their answer to this question is the foundation of the concept of a food chain.)
Ask students to predict what would happen if there were no green plants.
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