|Standards||NGSS K-LS1-1 What do plants need to survive?
NGSS 2-PS1-1 How do plants disperse their seeds?
NGSS 4-LS1-1 How does each part of the plant support survival, growth and reproduction?
- Magnifying glasses - 1 per partner pair
- Paper towels / napkins
- Soaked Lima beans - at least 2 per student
- Soaked variety of seeds - at least 2 pet student
- Clipboards, paper, and pens if doing dissection outside
This lesson can easily take place inside or outside without altering activities. Having a whiteboard and ample sitting space for the dissection activity is needed.
- Soak large Lima beans, plus a bowl of a variety of other seeds, in water about 12 hours prior to activity. Bring to class. If conducting the optional adaptation for 3rd-5th graders, soak one type of bean for a variety of different time periods ie. one batch for 5 days, one batch for 3 days, one batch wrapped in damp paper towels for one day.
- Familiarize yourself with basic seed anatomy and drawing the structures (refer to diagram example below).
1) Have the students break into pairs. Partnering with the person next to them at their workstations (whether inside or outside) works well here. Explain that together they will dissect seeds. Invite students to take four Lima beans from the bowl and two hand lenses and place them on paper towels in their work space. Be sure to allow students to explore other seeds (in addition to Lima beans) that have less obvious structures, such as peas and sunflowers, after their initial dissection of the Lima bean. It will take more time to find the structures in smaller seeds, but it is worth the effort for students to understand that all seeds have these parts and therefore all seeds have the possibility to become a plant.
2) Instruct students to investigate one of the beans they have placed on the paper towel with step-by-step directions. They may use their hands or other simple instruments you may provide such as toothpicks. Encourage the use of process skills by asking students to observe size, shape, number of parts, textures, etc.
3) Challenge them to identify the following parts (circle the vocabulary words on the board): seed coat (outer protection of seed - wrinkly and paper thin), embryo (part that will grow into the plant), and the cotyledons or endosperm (surrounds the embryo and is food for the baby plant until it is big enough to produce its own food).
4) Gently rub the seed between your fingers to remove the outer skin or seed coat. What is this and what is its function? (Seed coat and it protects the seed within it.)
5) Demonstrate how to split it in half by following the outer curve (looks like a rainbow!) with your fingernail or toothpick. Have students open and look inside their seeds using magnifying glasses.
6) Ask them to describe what they see in their seeds. Do you notice any patterns between different seeds? Are there any similar structures? Why might different seeds have the same internal structures? (Patterns; Asking Questions and Defining Problems)
7) Turn so that you’re facing away from the students and explain that you’ll be drawing a seed based on their descriptions, without looking at the seeds yourself. As they describe the seeds, draw one somewhere so that everyone can see it. For example, you might ask: Who could describe the shape of the seed? As one student describes it, draw whatever they describe. They can modify their descriptions based on how accurate your representation is. Then you might ask, Who can describe something they see on the inside of the seed? Continue until you have a full picture of a dissected seed. Ask students to draw a similar diagram of the parts of a seed and label it with you. Refer to the bean below for a simple and accurate representation:
Ask students to raise their hands to share
We have already identified the seed coat. (Label the seed coat on your drawing.) Inside the seed coat are large fleshy structures. What are these and their function?
Cotyledons, or endosperm, store food to help the plant grow until it produces true leaves. It feeds that baby plant while it’s underground. Sometimes we think of this as the seed’s “lunchbox.” Once the plant breaks through the soil and the true leaves emerge, it can start to gather sunlight and make its own food. What is this process called? (photosynthesis).
Cotyledons die back as the true leaves emerge to carry out photosynthesis. What happens if you plant a seed too deep?
What do they see in the inner curve of the cotyledons? It looks a bit like a tail. What is its function? (Baby plant or embryo, made up of the first true leaves and the roots. It is food for the baby plant until the first true leaves emerge to photosynthesize.)
- Seeds have a coat and a lunch box to stay warm, protected, and well fed while they grow underground!
- Refer back to the Learning Objectives for your grade level and ensure that they have been met by asking the given learning objective question.