Student's Pages
Activity 6: Are Seeds Food for plants?
Activity 6 - Teachers Page
Are seeds food for plants? Let's start thinking about this
question by observing some seeds closely.
Observe 2 or 3 different types of bean seeds, such as a lima bean
seed and a bush bean seed. What observations do you have about the seeds? What parts do the seeds have? What do
you think each of those parts does? Draw pictures of the parts you see. Label and describe the parts. Tell what you
think they do for the growing plant:
Draw or describe the seed parts you see.
What will each of these parts do for the growing plant?
Do you think the seed is food for plants? Why or why not?
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One way to get information about plants' food is by doing
experiments with plants. What ideas do you have about how we could do experiments with seeds to find out about how plants
get their food?
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Read the following description of an experiment with seeds. As
you read this description, think about what clues this experiment might give us about food for plants.
Bean Seed Experiment: Are seeds food for plants?
When you split a bean seed in half, you will find that a bean
seed has three parts. There is a little part that looks like a miniature plant. It called an EMBRYO and will grow into the adult
plant. The two large oval parts of the seed are called the COTYLEDONS:
In this experiment, you are going to put different parts of the
seeds on moist paper towels in a dish and observe them over the next few days.
1. First you will place a whole bean seed on the paper towel in
the dish.
2. Put a cotyledon with no embryo attached on the towel.
3. Put an embryo all by itself (no cotyledon attached) on the
towel.
4. Put a seed HALF that has both a cotyledon and an embryo
attached to it on the towel.
The picture below shows how the experiment will look. Fill in the
names of the plant parts on the lines next to the picture. #1 shows the whole bean seed. #2 is one cotyledon half.
It has no embryo attached to it. #3 is an embryo. It is not attached to a cotyledon. #4 is an embryo attached to one
cotyledon half.
Where does your group want to place your seed parts?
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Why?_______________________________________________________
Name____________________________
Bean Seed Experiment: Are seeds food for plants?
What are your predictions? Which seed parts will grow? Why do you
think so?
SEED PART
YOUR PREDICTION:
Will it grow?
REASON FOR YOUR PREDICTION
1. whole bean seed
2. cotyledon by itself
3. Embryo by itself
4. Embryo attached to one
cotyledon
5. Seed coat
Date Planted_______________________
Record the length of each seed part on planting day. Do it again
several times during your experiment.
DAY
EMBRYO
COTYLEDON
EMBRYO WITH
COTYLEDON
WHOLE SEED
Draw or tell what happened to the seed parts:
1. Which seed parts
grew?___________________________________________
2. Which seed parts DID NOT grow?
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3. Explain why you think some seed parts grew and others did not.
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4. Where do you think the growing embryo gets its food from?
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REFLECT AND CONNECT:
Developing An Explanation from The Bean Seed Experiment
How would a scientist explain these observations? A good
explanation for a science experiment does not just tell what you saw. A good explanation gives a reason why something
happened. Sometimes you have to think about things you cannot see to come up with a good explanation of what you do see.
Your observations of the bean seeds can be used as one kind of
evidence about how plants get food. Below are three possible explanations of what happened in the experiment. Decide
which one you think is the best explanation of the results or write a better one next to #4. Put a check by the best
explanation of this experiment, or write you own idea under #4:
_____ 1. The seeds with an embryo attached to a cotyledon grew.
The embryo alone did not grow. The cotyledon alone did not grow.
_____2. The embryo will grow when it is attached to a cotyledon,
because the cotyledon provides the embryo with food.
_____ 3. The embryo will grow when attached to a cotyledon,
because it needs the cotyledon to grow.
_____ 4. ________________________________________________________
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REFLECT AND CONNECT
A Science Discussion about the Bean Seed Experiment
Talk with the scientists in your class about this experiment.
What is the best explanation? Can you listen to each others' ideas and come to some agreement about what ideas this experiment
supports?
A SCIENTIFIC EXPLANATION:
How would a scientist think about this experiment?
A scientist would say that Number 1 is NOT a good explanation of
the experiment. This explanation only tells you what you saw happen in the experiment. It does not tell WHY this
happened. It does not give any reasons. It does not tell what might be happening inside the plant that could explain why the
embryo only grew when attached to the cotyledon.
Number 3 gives a reason. It says that the embryo grows only when
attached to the cotyledon, because it needs the cotyledon. But this explanation does not tell WHY the embryo
needs the cotyledon. It does not consider what might be happening inside the seed and embryo. It is not a very complete
explanation.
Number 2 is the most complete explanation. It gives a reason why
the embryo grows when attached to the cotyledon.
We cannot see the embryo getting food from the cotyledon, but we
can see that it grows only when attached to a cotyledon. One logical explanation for this is that the cotyledon
is giving food to the embryo. This explanation considers more than just what can be observed -- it imagines how our
observations might be explained by what is happening inside the bean embryo and cotyledon.
So Numbers 1 and 3 are not as complete explanations as Number 3.
They only describe what we can see. They do not talk about what might be happening inside the seed that could
explain WHY the embryo grew only when it had a cotyledon. Scientists try to explain their observations of plants
by thinking about what is going on inside the plant.
How would you explain how the growing embryo gets its
food?_________________
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REFLECT AND CONNECT:
Your Ideas About Food for Plants
Look back at what you wrote about how plants get food on your
pretest.
Think about our experiment with the bean seed parts. Think of any
other evidence that you and your classmates have collected on your data chart.
Do you have any new ideas to add to what you wrote? Or do you
want to change any of your ideas?
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