Student's Pages
Activity 4 - Our Inquiry: What is Food for Plants?
Activity 4 - Teachers Page
In our investigations about plants we will focus on questions
about how plants get their food: What is food for plants? How do plants get their food? How does their food
help plants live and grow? Do they need food in the winter? How can plants use food to change from tiny
seeds into large plants (bushes, trees, flowers, grasses, etc.)?
What is food?
In order to understand how plants get their food, you need to
understand a scientific meaning of the word “food.” This definition may be very different from what
you usually think of as food.
Write down how YOU would define food.
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In your definition, is juice a food? ___________
Is water a food? ___________
Is sugar a food? ___________
In everyday life, people have lots of ways of thinking about what
food is. When we think of food, we usually think about our own food -- not plants’ food. When we think
about food for people, some people would say that food is different from drinks. They would say that juice is
NOT a food, because you do not chew it.
Others would say that food is anything we “eat”, so
juice IS a food because it is taken into our bodies. Still others would say that juice is a food because it is good for us.
In everyday life, we can talk about food in these different ways and no one gets confused. We all know that
potatoes are food and that stones are not food!
But when scientists explore a question, like How do plants get
their food?, they need to all SHARE the same definition of food. Scientists have found out that things we
take into our bodies do many different things for the body. Water does not do the same thing for your
body that meat or sugar or aspirin or vitamins do. Scientists say that these things we “eat”
have different functions, or jobs, in the body.
So scientists have a special definition for food. Not everything
we take into our bodies is food by this definition. In our exploration about how plants get their food,
we will use this scientific definition of food:
FOOD is material that living things use for energy to live and
grow. All living things must use the energy in food to grow and to keep all their parts working properly.
The most important word in this definition is energy. Energy is
what makes all your cells and body parts work. It is what gives your body the power to breathe, to move
blood, to move muscles, to repair cuts, to build new cells, and so forth. Each cell in every living thing
has lots of work to do to stay alive, and energy is needed to get that work done. All cells of all living things need
energy. If your cells do not get energy, you will die.
Living things can ONLY get their energy from food. All living
things will die if their cells do not get food. Without food they have no energy to continue living.
Look back at your answers to the questions on the previous page.
How would you now CHANGE your definition of food?
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THINKING ABOUT WATER AND ENERGY: A ROLE PLAY
Because juice and sugar supply energy to living things,
scientists say that they are both food. Scientists would not say that water is food, because it does not have energy
in it that living things can use. Imagine yourself stranded in a place where you have lots of water but
nothing else to take into your body. What would happen to you after an hour? How would you feel? How about
after a day? Two days? Three days? longer?
1. Using our scientific definition of food, explain why you could
not live on water alone.
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2. People cannot live by eating dirt. Why isn’t dirt food
for us?
Use the scientific definition of food to explain your answer.
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3. Draw a picture to show how you think living things get their
energy: