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Rabbitbrush seed in flight
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Seed Travelers
Background
Plants and animals need each other to exist. Animals depend on plants
for food and shelter, and plants depend upon animals for obtaining
nutrients from their waste products and help with seed dispersal.
Many seeds are carried and dispersed by animals, catching a ride
on fur or perhaps eaten as a seed, fruit, or berry. Often, in island
ecosystems, birds are responsible for seed dispersal and carry the
first plant life into those isolated places.
Plants also take advantage of natural processes to assist in seed
dispersal. Wind and water are fundamental methods of seed transportation.
Some plants develop elaborate structural designs in order to keep
their seeds afloat for as long as possible.
Some plants, such as needle-and-thread grass (Stipa comata),
have the ability to plant themselves. After a seed is blown free
of its sheath, it falls to the ground. As the temperature and humidity
changes, the long awn (thread part of the seed) will twist and untwist.
The twisting motion will often bore it into the ground.
Procedure
In advance of your trip, divide the class into groups of three.
Each student will be assigned a specific type of seed dispersal
to look for: seeds that catch a ride on an animal's fur (these students
should wear fuzzy socks or corduroy pants on the day of the trip),
seeds that are blown by the wind, and seeds with other unique adaptations
(such as needle-and-thread grass).
On the day of your trip, choose an area in the grassland or where
the grassland meets the pinyon-juniper forest. Define boundaries
and let each group search for about ten minutes. Have students in
each group show one another what they found. It is permissible for
students to collect seeds for this activity, but they shouldn't
break any part of the rest of the plant.
Have each group classify their seeds according to dispersal method.
One student should record their findings in a group notebook. If
possible, they should try to find out what kind of plant their seeds
come from.
Each group will then take their most special seeds and show them
to the entire class. They should explain where the seed was found,
what plant they think it is from, and what they think the adaptation
for dispersal is.
Seeds should be released to the wind at the end of this activity.
Critical Thinking
- Discuss seed dispersal methods with your students. How many
can they think of?
- Is it possible that plants and animals have coevolved?
- How do plants develop such fantastic structures for their seeds?
Extension
Make
Your own Parachute - From the Science Museum of Minnesota
Adapted from Educator's Guide to Great Sand Dunes, by Lori
Cooper, Friends of the Dunes.
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