Standards: 4.2 Renewable and Nonrenewable Resources
Duration: 30 – 40 minutes
Vocabulary: dispersal, seed coat, growing conditions, competition
Summary: Students will study pictures of different seeds, how they grow, how they disperse over an area and why. They will then collect seeds to use in an art project.
Objectives: Students will learn about how plants use seeds to reproduce, and how those seeds travel from one place to another before they start to grow.
Materials: brown bags, black permanent marker, blanket
In the springtime, animals reproduce and have babies, which you can sometimes see out in nature. Animals are not the only things that reproduce, though—plants do too! Similar to how most animals start in eggs (think of a baby chick or turtle), plants produce young by growing seeds. The outside of a seed is called a ‘seed coat’ and inside each seed is a ‘baby’ plant, which will eventually start to grow. The seed coat protects the baby plant just like winter coats protect us from the cold in the winter. Before the baby plant grows, in many cases the seed has to disperse.
If a seed dropped right off a plant to the ground where the plant is already growing, the baby plant would have to compete with the adult one for water, food, and light. This isn’t good for the baby or the adult. Animals are able to avoid this by moving around to different areas. Plants can’t move on their own the way we can, though, so they have to rely on other dispersal methods. Some seeds are very small and have feathery tufts that can be carried far distances by the wind. Some have wings that make them spin around in the air and float away like helicopters. Some have very hard seed coats that give them time to be pushed around by rain and wind. Some seeds depend on animals to disperse them—either by getting caught in their fur or by the animal eating them and being passed through the digestive system.
Ask students if they have ever watched a bird or other animal eat a berry, if their dog has ever come inside with small ‘burs’ stuck to its fur, ever made a wish on a dandelion, or if they have ever eaten a fruit or vegetable containing seeds. All of these are types of seed dispersal!
Show students different pictures of seeds and discuss the method they use for dispersal. Some seeds use fluff to float on the wind, like dandelion and milkweed, while others have ‘wings,’ like maple seeds. Some are surrounded by tasty fruit that animals want to eat, and some use hooks to hitch a ride on fur on clothing to another location.
After reviewing the different kinds of seed dispersal found in this area, take students to an outdoor location. Fields and open spaces are ideal for finding seeds that are dispersed by the wind. Seeds with hard outer coatings can usually be found in forests.
Have students spend time collecting all of the seeds they can find that were dispersed by the wind or other methods. Another method is to have students take turns pulling a blanket through thick grass or un-mowed edges of fields. The seeds that have attached to the blanket can then be examined more closely. Allow students to collect these seeds into paper bags. The seeds can be used later in an art project.
Have students explain the different ways plants disperse their seeds. What does the word disperse mean? If you asked them to disperse, what action would they take?
Have students name the most common plants that use dispersal in their area.
Have students compare what they found on school grounds with what they find at home or on a field trip.
Try to grow some of the seeds at home or in the classroom.