The Great Escape
Students will identify ways that seeds are adapted to travel away from their parent plant.
Seed dispersal, adaptation
Pa. Standards Addressed Doing the Activity
- Teaching Methods Assessment and Evaluation
- Background Extensions
- Getting Ready Resources
Pennsylvania Environment and Ecology Standards Addressed:
- 4.7.4. Endangered, Threatened and Extinct Species
A. Identify differences in living things.
B. Know that adaptations are important for survival.
Other Pennsylvania Standards Addressed:
- Science and Technology
- Reading, Writing, Speaking and Listening
- Teaching Methods: Observation, classification, comparison, hands-on, small group
Planning & Planting Tips
- Include plants that have different types of seed dispersal methods.
- Wind – milkweed, maple, ash, basswood, dandelion, thistle
- Explosive – impatiens, witch hazel, jewelweed
- Animal express – oaks, cherry, other berries
- Hitchhikers – bidens, coreopsis
Parts of a Seed and Parts of a Flower attachments, divided plastic containers or egg cartons for seed collection, pieces of fuzzy cloth or old athletic socks, a variety of fruits, seed pods, and seeds
If you have ever blown the seeds off a dandelion, shot a watermelon seed out of your mouth, or popped the pod of an impatiens plant, then you have participated in seed dispersal. If seeds weren’t carried away from their parent plant, they might have trouble growing because they would compete for the same sunlight and nutrients. Seed dispersal also helps to spread the plant into new areas.
Seed production is a plant’s ultimate goal. It is the reason for sprouting, growing, and flowering. In fact it is the culmination of the entire growing process. Once a flower is pollinated and fertilized, a seed is produced. Flowering plants are called angiosperms, which means “to seed in a vessel.” The seed is a fertilized, ripened ovule and its container is the ripened ovary. Most plants produce a large number of seeds, but few will survive to sprout and grow. One cattail flower head can contain up to 125,000 seeds!
Seeds provide both food and shelter for the infant plant they hold. An inner layer surrounding the embryo stores enough food to nourish the tiny plant until its roots can draw their own nutrients from the soil and its leaves can photosynthesize. The outer seed coat protects the embryo from drying, freezing or being destroyed by an animal. Seeds require air, moisture, and heat to sprout and develop into a new plant.
Once seeds are produced and before they sprout, they are usually dispersed away from the parent plant for a better chance at survival. Since the plants themselves can’t move, seeds have developed amazing adaptations to help them get away.
Many plants depend on animals to help disperse their seeds. Some seeds are contained in fruits, which are carried by animal express. The animals eat the fruit and either discard the seed or pass them through their system. Cherries are eaten by birds, but the seeds pass through their system undigested. Some seeds actually contain protective coatings around them that prevent digestion, if they should be eaten by an animal. Gray squirrels bury acorns singly, but because they don’t eat them all, the seeds are planted and ready to germinate.
Animals also help to disperse seeds that hitchhike. These seed containers have hooks, barbs, or sticky coatings that catch in an animal’s fur and are carried with them as they travel. The burdock bur is covered with small curved hooks which easily penetrate fur or clothing, but hold tight once hooked. When an animal tries to remove the bur, the sheaths that hold the seeds separate and release them.
The wind is also an important seed disperser. There are seeds with propellers that slow their fall so the wind can carry them. Maple, basswood, and ash have these types of seeds. Other seeds have fluffy hairs that act as parachutes which transport them on wind currents. Dandelion, milkweed, and poplar seeds can travel long distances this way. Milkweed seedpods split open so the wind can catch a few seeds at a time.
There are also seeds that float on water, which can carry them far away. Coconuts float in the ocean for many miles before landing on a shore and germinating. Still other plants have seeds that burst open with tremendous force. Jewelweed and witch hazel plants produce these powerful seedpods. A witch hazel pod can shoot its seed up to 40 feet!
Seeds can travel several miles on the wind, several hundred miles on water, and several thousand miles if carried on a bird. But whatever the method, the end result is the same, seeds must travel far enough from their parent plant to meet their needs and avoid competition.
Collect a variety of fruits, seed pods, and seeds.
Doing the Activity
In the classroom
- Using information from the background section and the Parts of a Seed and Parts of a Flower sheets discuss the parts of a seed, their function, and how they are formed.
- Show students a variety of fruits, seed pods, and seeds.
In the garden
- Ask students to observe the plants and look for seeds. Point out some of the different types of seed pods or fruits that would contain seeds.
- Take students to the garden. Tell students they will be going on a seed search. Break the students into pairs. Hand out divided plastic containers or egg cartons. Tell them it is their job to fill each compartment with a different type of seed, seed pod, or fruit. Have students collect seed pods, fruits, and seeds from the ground or carefully remove them from the plants. (Some pods, like impatiens, are sensitive and may burst if touched. Tell students to carefully scoop the pod into the container.)
You can also hand each pair of students a piece of cloth or an old sock. Explain that they can drag the cloth through the plants or put the sock over their shoes to collect seeds that will stick to it. If time permits, also have students collect seeds from a natural area or from plants around the school grounds.
In the classroom
- Join pairs together to form small groups. Have each group combine the seeds they collected. If necessary, supplement with the seeds you collected in advance to insure variety. Ask the students the following: What do all the seeds have in common? Why are there so many different kinds of seeds/seed containers? Discuss the importance of seed dispersal as a way of avoiding competition with the parent plant.
- Have students discuss how they think each type of seed might be dispersed. Have them group the seeds by the type of dispersal method used. Have each group select a type of seed and demonstrate to the class how the seed is dispersed. As students demonstrate a seed dispersal method, have the rest of the class guess what type of method is used. After each group demonstrates a method, list it on the blackboard. Ask students why there are different types of dispersal methods? Are there any other seed dispersal methods we can add to our list? Have you ever played a part in seed dispersal?
- Have each group select a seed pod or fruit and open it to locate the seeds. Have students record the size, shape, color, and approximate number of seeds. Ask students the following questions: Do some plants produce more seeds than other plants? How do the seed’s size, shape and/or number affect its dispersal? How far can a seed be dispersed? Why is distance important?
- Correct demonstration of seed dispersal method.
- Have students use their journals to list the different types of seed dispersal and give examples of a type of seed that uses a specific method.
Have students design seeds with specific dispersal methods. Give each student a dried bean as a base. Provide a “junk” box of craft materials (craft sticks, rubber bands, string, cardboard, etc.). Give students a card that challenges them to design a seed that does one of the following: floats on water for 5 minutes, glides in the air for at least 10 seconds, sticks to an animal and is carried 10 feet, is shot like a cannonball at least 2 feet away, or attracts a bird or animal to carry it away.
Send students on a seed scavenger hunt. Provide cards that list items such as: seeds that stick to your clothing, seeds that travel 3 feet when you blow on them, seeds that provide food for an animal, seeds that have parachutes or wings to carry them, seeds that are bigger than a dime, seeds that are hairy, etc.
Ask students to pretend to be a seed. Have them write a poem or story about their experience traveling from their parent plant to the place they would land and grow.
- Lingelbach, Jenepher, Vermont Institute of Natural Science, Hands-On Nature, 1986
- American Forest Foundation, Project Learning Tree, 1993
- Parrella, Deborah, Project Seasons, 1995
- Stokes, Donald, Nature in Winter, 1976