Hitching a Ride

Engage (15 minutes):

Ask students to help you solve a confusing problem: How can a tree grow by itself in the middle of a field if no one planted it there?  We know that trees grow from seeds, but if there are no other trees around, then how did the seed get there?  Record student responses on the board or a class chart.  (This will also serve as an informal assessment of students’ prior knowledge.)

Tell students that even if a person didn’t plant the seed, it might have been transported by someone else (an animal).  Explain that students model this process by having a relay race to transport seeds from one side of the room to the other.  Each team will have a different type of seed to carry, and the team that successfully transports all their seeds first wins.  Students are pretending to be animals for this race so there is a catch--they cannot use their hands for this challenge.

Divide class into teams of four students.  Give each person on the same team the same type of seed.  Before beginning the relay, give each group a few minutes to brainstorm a transportation strategy.

After the relay, debrief by asking the following questions:

• Which seeds seemed easiest to carry?  Why?
• Which strategies worked best for transporting the seeds?  Why?
• What does this relay race relate to my original question, “How does a tree grow by itself in the middle of a field if no one planted it there?

Explore (30 minutes):

Tell students that they are going to look closely at seeds to see how the properties of the seeds might help them move from one place to another.

Create six seed stations.  (This portion of the lesson is adapted from ExploringNature.org.)  Materials for each station:

• 1-2 hand lenses (depending on the size of your groups)
• A paper plate containing one type of seed (acorns, maple seeds, nuts in shells, fruit seeds, flower seeds, vegetable seeds, a whole coconut, etc.).  Label each paper plate with the type of seed it contains.
• A bowl of water
• A fuzzy stick or pipe cleaner
• A fuzzy sock or piece of faux fur

Distribute copies of observation chart.  Divide students into small groups and rotate through the stations.  Have students spend about 5 minutes at each station to complete the following activities:

1. Observe the seeds with a hand lens.
2. Draw and label the seed, discussing its size, shape, and texture within their groups as they observe.
3. Test the seeds to see if they float in water.  Remove seeds from water and dry them with a paper towel.
4. Test seeds to see if they stick to the fuzzy stick, sock, or faux fur.
5. See if the seeds are easy to blow off the plate.  Have students drop a seed from an arm’s length over the plate to see if it drops straight down to the plate or drifts away from it. 
6. Answer questions on Seed Observation chart and conclude how each type seed is most commonly transported based on evidence from their observations.

Explain (20 minutes):

Watch “Seed Song – How Seeds Move” YouTube video.  (You may want to print the lyrics of the song for students.  You can access the lyrics by clicking “See More” under the video.)

Divide students into groups of four and give each group a large piece of paper.  Have each group list all the ways seeds can move from one place to another.  Encourage them to think of possibilities listed in the song as well as other ways they imagine seeds are transported.  (Examples listed in the song include an acorn being buried and forgotten by a squirrel, a coconut falling in the water, a maple tree seed flying on the wind, and burrs getting stuck to people’s socks.  Possible examples students may think of include blowing dandelions, seeds getting stuck in animals’ fur, animals eating seeds and pooping them out, etc.)

Have each group read its ideas aloud to the class.  As students report their ideas, create a two-column chart where students classify their transportation methods as “With Animal Help” or “Without Animal Help.”

Show students The Seed Site.  Look at the pictures of seeds and read how animals transport each type of seed.  Have students discuss the properties of seeds that would promote transport by particular methods.  (For example, seeds within tasty fruits are often eaten and spread through animal droppings, sticky or prickly seeds stick to animals’ fur or feathers.)

Elaborate (45 minutes):

Have students use their knowledge of the ways animals transport seeds and the engineering design process to come up with an animal structure to help them win the seed transportation relay race from the beginning of the lesson.  Have students look closely at the different types of seeds and choose the type that they think will be easiest to transport. Have them explain their choice, naming properties of the seed as evidence to support their choices.

Display a list of available materials and explain the challenge further.  Students can make an entire animal, or they may make the part of the animal essential to transport the seeds.  For example, they may create a bird beak that they can manipulate to pick up seeds, or they may use the fur to create a small chipmunk.

Guide students through the engineering design process: (You may use the Engineering Design Process planning guide included in the Attachments section, or you may have students record these steps in their science notebooks.)  Students can work on this solution as a complete team, or they can work in pairs so each team can try multiple solutions.

• Ask: What’s the problem?  I need to carry my seed quickly. What are the constraints? I cannot use my hands.  I need to make an animal or animal structure with the materials given to transport the seed.
• Imagine: What animal structures would do the best job transporting my seed? How can I make these structures with the materials given?  Brainstorm possible solutions.
• Plan: What materials do I need?  What will my solution look like?  Draw it.
• Create and test.  Give students time to create their solutions and test them in the relay race.
• Improve.  After the race, give students time to discuss how they can improve their animals and/or animal structures.  Race again to test these modifications.