- Big Ideas
- Essential Questions
- Content Outcomes Addressed
- Standards Addressed
- Pre- and Post-Assessment
- Investigation 1: Whirlybird
- Investigation 2: Observations
- It is beneficial for plants to spread their seeds far and wide.
- Plants employ a variety of mechanisms to disperse their seeds.
- Why do plants disperse their seeds?
- How do plants disperse their seeds?
Content Outcomes Addressed
- Students will develop an understanding of mechanisms of seed dispersal.
- Students will understand ways in which seed dispersal benefits a plant.
- Disciplinary Core Ideas: LS1.A (K-2), LS1.A (3-5), LS1.B (K-2), LS1.B (3-5), LS2.A (K-2), LS3.A (K-2), LS3.A (3-5), LS3.B (K-2), LS3.B (3-5)
- Science and Engineering Practices: 1, 3, 4, 6, 7, 8
- Crosscutting Concepts: 1, 2, 4, 6
- Writing: W.K.7, W.K.8, W.1.7, W.1.8, W.2.7, W.2.8, W.3.8, W.4.8
- Speaking and Listening: SL.K.1, SL.K.3, SL.K.4, SL.K.5, SL.K.6, SL.1.1, SL.1.3, SL.1.4, SL.1.5, SL.1.6, SL.2.1, SL.2.3, SL.2.4, SL.2.6, SL.3.1, SL.3.3, SL.3.4, SL.3.6, SL.4.1, SL.4.3, SL.4.4, SL.4.6, SL.5.1, SL.5.3, SL.5.4, SL.5.6
- Mathematical Practice: MP.3, MP.7
- Measurement & Data: K.MD.B.3, 1.MD.C.4
Wind, water, and animals are all helpful in dispersing seeds.This is important so that plants will have enough space, sunlight, water, and nutrients to grow. Lightweight seeds are blown by the wind to new places. Sticky seeds or seeds with hooks get stuck to the hair or skin of animals and get moved to new places before they fall off. Other seeds are moved by running water, and still others that are located inside the fruit are eaten by animals, pass through their digestive tracts, and are deposited in other locations.
- seed: part of the plant that contains the beginnings of a new plant that will grow if exposed to the proper conditions
Pre- and Post-Assessment
Assess prior knowledge by asking students why it might be better for a plant to disperse its seed far away. Also ask if they can imagine different methods through which seeds are transported, or if they already know any of these methods. (They should probably know fruit). Have students repeat this activity after the unit of study.
- Plants just drop their seeds, and their offspring grow right next to them.
- All plants rely on fruit as a means of seed dispersal.
Investigation 1: Whirlybird
- Notebooks and pencils
- Whirlybird cutout (print out from Resources, above right)
- Paper clip
- Using the background information above, explain seed dispersal to the students. They should jot down the different methods of dispersal in their notebooks.
- To show how seeds are dispersed by the wind, make a paper “whirlybird,” using the pattern provided in Resources (above right), scissors, and a paper clip. Cut on the dashed lines only; fold on the solid lines, following the directions. Have the students drop the completed whirlybird to demonstrate how a seed is carried by the wind.
- Encourage more design-minded students to try other paper shapes to see how these fare compared to the whirlybird.
Investigation 2: Observations
Materials (use three or more of the following; if possible, collect them with the students):
- A few different types of fruit (with seeds)
- Other types of seeds
- If the season is right, go outside and explore nearby plants (again, either within or outside of your garden). Note how seeds are transported, and where they are in the plant.
- Next, take a closer look at seeds themselves. In the classroom, lay out a variety of different seed types.You can prepare them beforehand, or, if local ecology permits, gather them with students. Either way, note what plant each seed comes from. Have students use as many of their five senses as is safe to examine the seeds. Be especially careful with the sense of taste.
- Separate students into groups. Have each group hypothesize how they think each collected seed is transported (e.g. burrs attach to fur, fruits are eaten, dandelions disperse via wind, etc.).
- Ask each group to share its findings. When there are disagreements, ask the students to justify their answers. At the end, share the correct mechanisms.
- Also discuss mechanisms for which you could not find anexample. You can find many here: http://www2.bgfl.org/bgfl2/custom/resources_ftp/client_ftp/ks2/science/plants_pt2/dispersal.htm.
In the region that surrounds Mpala a cactus called opuntia, which was introduced to Kenya from the United States, has begun to outcompete native plants. This makes it an invasive species—one that not only is not native to an environment but is also damaging to it. Opuntia has spread because so many animals— from elephants to monkeys—eat its fruit and then disperse its seeds through their dung. Are there any invasive species in your region? Investigate this question with your class, and discuss how the seeds of the invasive species are dispersed. Also discuss whether—and how—this species can be controlled.