|Students will investigate different methods of seed dispersal and their importance to the survival of plants' offspring. Students will use a magnifying glass to make observations about the features of different seeds. Students will begin to compare how humans (farmers and gardeners) disperse seeds as well.
|Standards and Benchmarks
- Tools such as thermometers, magnifiers, rulers, or balances often give more information about things than can be obtained by just observing things without their help
- In doing science, it is often helpful to work with a team and to share findings with others. All team members should reach their own individual conclusions, however, about what the findings mean.
- Tools are used to do things better or more easily and to do some things that could not otherwise be done at all. In technology, tools are used to observe, measure, and make things.
- Some animals and plants are alike in the way they look and in the things they do, and others are very different from one another.
- Plants and animals have features that help them live in different environments.
- Students should be able to draw pictures that correctly portray at least some features of the thing being described.
- Students will be able to explain the different ways in which a seed may reach a specific location.
- Students will be able to explain that some seeds have specific adaptations for dispersal.
- Students will be able to look at seeds and identify their most likely method of dispersal.
- Students will be able to use a magnifying glass to observe a seed up close.
|Class Time Needed
|45 minutes each day for 3 days
|If you haven't already, you can prepare a plant notebook for each student for the entire unit by downloading the Plant Notebook Worksheets. The worksheets can serve as the pages of the plant notebook. Students can use these worksheets to record their predictions, observations, and explanations for each lesson. Assessments are also included in the worksheets.
- Various types of seeds with unique adaptations for dispersal. (Examples of types of seeds that can be used as well as links to pictures of these seeds can be found in the Science Background section.)
- Plant notebooks
- Magnifying glass (1 per group)
- Adult socks (~1 for each student)
- Sacks (brown paper lunch sacks or plastic bags, 1 for each student)
- Plant notebooks
- Magnifying glass (1 per group)
|The worksheets for this particular lesson are on pgs.9-14 in the file Plant Notebook Worksheets
What is seed dispersal?
Seed dispersal is the method by which seeds are moved from one area to another. Dispersion puts space between growing plants, decreasing competition for resources and increasing their chances of survival. The four main types of dispersal are wind, water, animal, and explosion.
There is an enormous amount of diversity on earth. Environmental conditions affecting plant growth vary widely across the planet. The types of plants and the physical characteristics of plants in a particular place vary in relation to the amount of sun, the amount of water, the type of animals and other plants present, and the weather, among other factors. Plants in different environments have features which allow them to grow and survive in the particular set of conditions they face. These features may be the result of adaptations, or changes, over time. Plants with features suited to their environment are most likely to survive and reproduce.
- Some plants produce seeds that have hair-like parachutes or helicopter wings. These types of seeds can be transported by the wind. The wind helps keep the seeds aloft during flight, delaying their fall to the ground. This delay allows seeds to be carried from the parent plant.
- Plants that grow in or near water can use water to transport their seeds. Plants drop their seeds into water, and the water can pick up seeds that are buoyant and deposit them away from the parent plant. Seeds can be dispersed long distances in this way.
- Animals can also transport seeds. First, many plants produce fruits that contain seeds, which are then eaten by animals such as birds and mammals. The seeds usually pass through the gut of the animal and are not digested. Animals then deposit the seeds in new areas through their droppings. Second, seeds that have hooks or seeds that are sticky can easily cling to animals that brush up against them. The seeds eventually will fall off the animal, being deposited away from the parent plant.
- Finally, the seeds of some plants can be dispersed by explosion. Forceful ejection of seeds occurs when a pod dries up and splits. Seeds are dispelled when the pod bursts open. In this way seeds can be expelled far from the parent plant.
Below is a list that shows the different methods of seed dispersal as well as some examples of each kind of dispersal. Also pictures of the different kinds of seeds can be found at the following websites: (Fruit & Seed Dispersal: Steve Baskauf, 2002) and (Seed Dispersal: Offwell Woodland and Wildlife Trust, 2003) and (Seeds and Fruits Dispersed by Wind: Wayne's Word, 1999)
Methods of Seed Dispersal
- Helicopter Wings: sycamore, maple, and ash seeds
- Hair-Like Parachutes: dandelions, cattails, milkweed
- Clings to Fur Via Hooks: cockleburs
- Sticks to Fur: mistletoe
- Eaten: berries, nuts
- Forceful Ejection: touch-me-nots, witch hazel
|Students' Alternative Ideas
Alternative idea: Many students are not sure whether seeds are alive or not. Seeds "moving" during dispersal may add to their confusion.
Scientific idea: A seed is not considered a living organism. A seed has the potential for giving rise to a new organism; without the presence of appropriate conditions, a seed will not germinate and instead will stay dormant. Once a seed is germinated, it is considered to be alive.
Dealing with the alternative idea: Make sure to focus on the fact that seeds are dependent on other organisms (animals) or nature (wind) in order to disperse seeds.
| Day 1
1. Initiate discussion by telling students a story about a flower that just appeared in your yard. Tell them that you never planted any flowers, and have no other ones anywhere in your yard. Ask them how it could have gotten there.
2. Allow students to discuss possible methods of seed transportation, facilitating discussion when needed. Also, discuss WHY seed transportation is important For example, you might ask, "Why can't all the acorns that fall off of a tree sprout and grow right where they fell?" Possible answers for why seed transportation is important include:
3. Have students get in groups of 2-3 and present them with various types of seeds. Give each group a magnifying glass and ask students to observe the seeds carefully. Ask students what magnifying glasses are used for. Make sure they understand that magnifying glasses make objects appear larger and allow us to see things we might not be able to see with our eyes alone. Have students think of examples of professionals who might use this scientific tool.
- The seeds can be spread to new places.
- The seeds can be spread to places where there are more resources (better soil, more sunlight, etc.)
- The seeds can be spread to safer places (so animals cannot kill all the new plants.)
4. Rotate among the groups, asking questions about their predictions and facilitating discussions as needed. Have students predict each seed's most likely method of travel.
5. Have students record this information in their plant notebooks. (See the Worksheets section to download this lesson's worksheets.) In particular, have students:
By writing about how they think their seed travels, students are stating a CLAIM about WHAT they think. However, it is also important for students to use EVIDENCE to explain WHY they think their seed travels a particular way. For example, students can use their observations of their seed's features as evidence to support their claim. They might also have read about seed dispersal in a book or have a tree with those particular seeds in their backyard. Thus, students can also use something they've read or their prior experiences as evidence. In either case, help students always make complete explanations by having them state a CLAIM followed by some EVIDENCE.
- Write about at least one what kind of seed they observed
- Draw a picture of it (using specific details)
- Write or draw how they think it travels
- Write WHY they think it travels in this way.
1. Ask students to think of animals that might walk through fields or parks in their neighborhood or in empty areas. (Most common will be dogs, cats, raccoons, squirrels, mice, deer, foxes, birds, etc.) Tell students that they will pretend to be one of these animals today.
2. Pass out one adult sock and plastic bag/lunch sack to each student. Have them put the sock over one shoe.
3. Tell students that they will be going on a nature walk to collect seeds: Encourage students to walk over and through many types of plants as animals would so that their socks can collect seeds like an animal's fur would. Tell them that they will also need to carefully look on the ground and in the air for seeds. Explain that they will collect these seeds in their bags. Have students keep the seeds that stick to the socks separate from the seeds they put in their bags.
4. Make sure to discuss behavior, safety, and observation expectations with students before going outside. (This activity works best in a place where trees and several different kinds of plants grow, such as an open field or a weedy section of a playground. If you only have access to a uniform grassy area, try this activity before scheduling it with your students.)
5. Bring students in from the walk and have them remove their socks. (Remember to have the students keep the seeds on the sock separate from the seeds in the bag!)
6. Have students work in groups to determine which items that they have collected are actually seeds. Give each group a magnifying glass and ask students to observe the seeds carefully. Have them then decide how their seeds might be moved. Rotate among the groups, asking questions about their predictions and facilitating discussion as needed.
7. Have students choose two seeds from their sock and two seeds from their bag and tape them into their plant notebooks. Then have students record the following information in their plant notebooks:
Remember that it is important for students not only to state WHAT they think by making a CLAIM but also to explain WHY they think what they do by giving some EVIDENCE for their claim. For example, students might make the CLAIM that dandelion seeds are moved by the wind. Students can then use their observations of the seed parts (e.g., the feathery hairs on the seed) as EVIDENCE to explain WHY they think their seed is moved by the wind. In science, claims are judged by how strongly they are supported by evidence, so help your students to always use evidence to support their claims so they can practice making strong explanations.
- Their prediction for how each of their seeds travels.
- Their explanation for why they think their seeds travel in the way they predicted.
8. Optional: Some students could research more sophisticated methods of seed dispersal; specific examples include the Proteas (depends on fire), the Squirting Cucumber (squirts its seeds out when it comes in contact with water), and the Himalayan Balsam (flings its seeds).
- Why should students collect evidence to answer questions?
- How can I help my students collect evidence?
1. Have students design their own made-up seed with specific traits, having it disperse in a specific way. Help students make a distinction, if they haven't already, between seeds dispersed by humans and seeds that are dispersed by animals/natural forces.
2. Have students record the following information about their seed in their plant notebooks:
3. Have students share their seed creations with the class. During the presentations, listen for students' understanding of both HOW seeds move and WHY they think their seed can move in this way. Prompt students with the following questions:
- Draw a picture of your seed.
- Describe how your seed moves (the method of dispersal).
- Tell us if your seed depends on other animals or nature (water or wind) in order to move.
- Explain WHY you think your method will work.
- Explain why your seed needs to be able to move (to be dispersed).
(Possible Answer: Students might describe their seed as being covered with hooks.)
- What does your seed look like?
(Possible Answer: Students might make the CLAIM that their seed is moved by animals.)
(Possible Answer: Students might suggest that their seed is moved by animals BECAUSE they saw similar seeds during their seed walk that had hooks on them and that stuck to their sock. Thus, this question prompts students to use their previous observations and experiences as EVIDENCE to support the above claim.)
- Why do you think your method will work?
Why should students draw conclusions based on evidence?
How can I help students draw conclusions based on evidence?
Why should students communicate and justify their findings?
How can I help my students communicate and justify their findings?
|1. On Days 1 and 2, students will be assessed on their plant notebook entries and their participation in small groups.
2. On Day 3, students' ability to make explanations using evidence will be assessed by having students answer questions in their plant notebooks about the seed they designed and by having students present their seed to the class. (See the Worksheets section to download this lesson's worksheets.)
The questions that students will be responsible for answering in their plant notebooks and in their presentations are found under the heading for Day 3 and are also listed below.
- What does your seed look like?
- How does your seed move?
- Does the seed depend on other organisms or nature (i.e. wind) to disperse the seeds?
- During your seed activities, what did you do or see that makes you think your seed can move in this way? (This question is a WHY question in disguise. Even though the word WHY doesn't appear in the question itself, it still is asking students to use evidence to support their answer.)
- Give one reason why your seed needs to be able to move.
|Images of Inquiry
Click here to find out how you can customize this lesson.
This lesson focuses on Explanations & Evidence.
How Catie taught this lesson
Before I discuss the method of organization that I suggest, let me mention first that I modified this lesson slightly. Due to time restrictions and unavailability of parks to search for seeds, I did not have the children gather seeds but instead gave them seeds to figure out their methods of movement (water, wind, sticking).
My second graders have been working all year on placing data in different organizational formats. In doing this activity, I wanted them to apply a method that they were already familiar with, creating a data table with titled columns. Let me emphasize that the idea was not for the children to follow a set format in creating their data table but to make it clearly organized so others could understand it and/or so the students could explain it to others even after coming back to it after several days. I thought this was difficult, however. When I monitored each child carefully, I could get the majority to produce some good work. Although the charts weren't perfect, it gave the children practice using organizational methods that they have been exposed to. It was important for them to apply these methods in order to become more comfortable with and skilled at using them. Another great advantage of this lesson was that the children were encouraged to apply organizational methods to increase their learning about how seeds move and were being challenged and thus had opportunities to improve on their fine motor and spatial skills.
How Peg taught this lesson
Peg's 1st graders loved the sock walk. They were talking excitedly when they got back to the classroom and eagerly began removing seeds from their socks. However, when they began drawing their ideas about how their seeds moved, the students found this difficult. They could come up with ideas about how seeds travel, but Peg noticed that their ideas weren't connected to specific seed features. So Peg decided to introduce her students to the term "evidence." Each student chose 1 seed and gave their opinion (or claim) about how it traveled. Then, the class asked the person what their evidence was. The student then had to point to a feature on the seed that supported his or her claim. This established an important ritual in their classroom -- supporting explanations with evidence -- that will be important throughout this unit. It also helped guide students through this difficult task.