Lesson 3: Seed Dispersal

Materials

• Notebooks and pencils
• Whirlybird cutout (print out from Resources, above right)
• Scissors
• Paper clip
• Seeds

Procedure

1. Using the background information above, explain seed dispersal to the students. They should jot down the different methods of dispersal in their notebooks.
2. 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.
3. Encourage more design-minded students to try other paper shapes to see how these fare compared to the whirlybird.

Materials (use three or more of the following; if possible, collect them with the students):

• A few different types of fruit (with seeds)
• Nuts
• Dandelion
• Burrs
• Other types of seeds

Procedure

1. 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.
2. 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.
3. 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.).
4. 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.
5. 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.

Invasive Species

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.