Cascades to Coast GK-12 Curriculum
Seed Dispersal and Design
Fellow: Christa von Behren and Jill Van Winkle (Environmental Science and Management)
Teacher: Linda Wolf (Glencoe HS) and Kimberly Crowell (Cleveland HS)
Advisor: Alan Yeakley and Marion Dresner (Environmental Science and Management)
Learning Goal:
Learn about multiple adaptations for dispersal, resource partitioning, interactions between seeds
and biotic and abiotic ecosystem components, and ecological tradeoffs through hypothesis
testing and model design.
Students Learning Objectives
- To learn about the role of dispersal in plant ecology
- To lean about adaptations for seed dispersal and survival
- To learn about interactions between different seed designs and biotic and abiotic
ecosystem components
- To learn about resource partitioning in seed design
- To test multiple ideas about seed design
- To compare contrasting student models to demonstrate multiple means of achieving an
ecological goal
Target Grade: 9th Grade biology or integrated science
Next Generation Science Standards:
HS-LS1-2: Develop and use a model to illustrate the hierarchical organization of interacting
systems that provide specific functions within multicellular organisms.
HS-LS2-2: Use mathematical representations to support and revise explanations based on
evidence about factors affecting biodiversity and populations in ecosystems of different scales.
HS-LS4-3: Apply concepts of statistics and probability to support explanations that organisms
with an advantageous heritable trait tend to increase in proportion to organisms lacking this trait.
HS-LS4-4: Construct an explanation based on evidence for how natural selection leads to
adaptation of populations.
Unit Summary
This unit includes two activities: Seed Dispersal and Design-a-Seed. Seed Dispersal can be
completed as a stand-alone activity; however, Design-a-Seed builds directly on skills learned in
Seed Dispersal. Seed Dispersal is designed for one 75-80 minute class period. Design-a-Seed is
designed for two 75-80 minute periods, but it could be condensed into one.
Activity 1: Seed Dispersal Mechanisms
Students observe and categorize seeds by dispersal type(s), generate hypotheses, test
seeds. Additional background for this activity:
http://floridadep.org/secretary/ed/life/collier/default.htm
Activity 2: Design-a-Seed
Students use various provided materials to create a seed, test dispersal, and present seed
design results and rationale.
Activity 1: Seed Dispersal
Activity Plan
This activity is designed to be completed in a 75-80 minute class period, but can relatively easily
be adapted to fit two 30-40-minute class periods. A short overview of seed dispersal is presented,
with students answering questions from a worksheet (see link). Then the activity is reviewed,
with demonstrations of each task. The activity ends with students graphing their results on the
board and a short discussion. The goal is to better understand the many varied mechanisms by
which plants disperse their seeds.
Materials needed:
- Variety of seeds! Berries, coconut, and many locally collected wind, water, and animal
dispersed seeds, e.g. acorns, maple samaras, weed seeds, clematis (works great and is
often available throughout fall and winter), burdock, bedstraw, dandelions, large-leafed
avens, etc (see link for seed images).
- Dissecting scopes
- Hand lenses
- Forceps
- Petri dishes or other containers for seeds under the scopes
- Stop watch
- Basin or buckets with water
- Measuring tape
- Meter sticks
- Large box fans
Introduction Presentation (~10 minutes):
The activity begins with an interactive presentation. Students follow along with their worksheet
and answer questions as prompted (see Appendix for sample worksheets). Topics overviewed:
1. What is a seed? A fruit? Why do plants need to disperse seed? Basic introduction to
fruit/seed structure and function.
2. How are seeds dispersed? Ask students and show photos to identify all methods. Use a
real example (e.g. How is a coconut dispersed? Demonstrate with a bucket of water. Why
is this a good strategy for a coconut?)
a. Gravity
b. Wind
c. Water
d. Ballistic (shatter)
e. Human/animal: hitchhikers fur/hair/clothing
f. Human/animal mediated: food
g. Combination?
3. Invasive plants seed dispersal. If you were not adapted to the local ecosystem, what
methods would you use?
Activity (see handouts for data collection and reporting) (~50 minutes total)
Part 1: Hypothesis Development (~20-25 minutes)
Students are split into groups of 2-4. Each workstation should have a dissecting scope and/or
hand lens. Students should select at least 4 different types of seeds and make observations on
page 2 of the activity worksheet. Using dissecting scopes as needed: describe and draw seeds,
identifying characteristics that might aid in dispersal. From observations, students develop
hypotheses about how each seed is dispersed and record on worksheet.
Part 2: hypothesis testing (~20-25 minutes)
Students test seeds for each dispersal mechanism and record results on page 3 of the worksheet.
Categories to be tested:
1) Dispersal through air - measured by timed drop test
2) Wind dispersal along the ground – distance travelled from a fan
3) Animal dispersal – time seed remains attached to a shaking piece of cloth
4) Water dispersal – float time in water bucket
Report results to class (~10 minutes)
After testing, students will graph their data on a group plot at the front of the class to compare
results. Students will present their drawings and discuss if their results supported their
hypotheses. Encourage students to talk about specific structures of the seeds that facilitate
dispersal. What structures work best? Why? Were there any seeds that worked well with all
dispersal methods tested?
Related Concepts: Adaptations and evolution, plant-animal interactions, reproductive strategies,
invasive species.
Extensions: Investigate dispersal mechanisms used by invasive plant species (e.g. English ivy,
yellow star thistle; Oregon Field Guide’s Silent Invasions video would be an excellent
introduction). Investigate how plants disperse other than by seed. Study how some plants adapt
dispersal highly specific to their habitat.
Activity 2: Design-a-Seed
Activity Plan
This activity is designed to be completed in two 75-80 minute class periods, although it could be
condensed into one. On the first day, seed dispersal is reviewed, the contest goals are presented,
and students build their seeds. The goal is to build a seed that maximizes both seed size and
dispersal distance through one or more mechanisms. During the second class period students
compete with their seeds in different tests. Test results are graphed and discussed.
First Class Period (80 min) – Seed construction
Before the construction activity begins, there is a short (5-10 min) review of seed dispersal
vectors and strategies. Pictures of different seeds are shown.
Students are then broken into small groups (2-4 students) for the seed building activity. The
groups at this point are told what their design goals are. Each group can try to create the best
general disperser and compete in all dispersal categories while trying to maximize seed size.
Alternatively, groups can be assigned a single dispersal mode that they are trying to maximize in
addition to seed size.
Categories to be tested:
1) Dispersal through air - measured by timed drop test
2) Wind dispersal along the ground – distance travelled from a fan
3) Animal dispersal – time seed remains attached to a shaking piece of cloth
4) Seed size – mass of seed
The class is shown the building materials available, and each group is asked to plan their seed on
a worksheet. All designs must incorporate a small glass bead which represents the embryo of the
seed. The teacher approves the design worksheet for each group and then provides building
materials. Groups are allowed the rest of the class period to complete their seeds. Students are
allowed to drop and toss their seeds, but they are not given access to the “official” competition
testing instruments.
Suggested building materials: wire, Styrofoam balls, construction paper, confetti, feathers, pompoms, string, beads, tissue paper, Velcro
- All groups should be provided with the same amounts of all materials.
-Glue should be avoided if testing is to happen in the same class period.
-If tape is allowed it should be in a standard amount for each group.
Second Class Period (60-80 min) – Seed testing
At the beginning of class groups are given a short time period (~10 min) to make any final
adjustments to their seeds. Then the testing begins. Teachers should run all tests with students
recording data.
For the competition, the following measurements are taken:
1) Seed mass using a balance
2) Time for the seed to drop from a standard height to the floor – should be at least 6 ft.
3) Distance travelled along the floor when placed in front of a small fan – stretch a tape measure
out along the floor. The seed is placed at 0 with the fan behind.
4) Time it stays attached to a piece of cloth (fake fur, flannel, felt, wool, etc.) shaken by the
teacher.
Students should record data for all seed tests in notebooks or on a worksheet. Seeds are
measured and ranked for each category, with the largest value (time, distance, mass), receiving
the most points. The maximum number of points for each dispersal category can be equal to the
number of seeds competing in that category. The scores of each category (either all dispersal
modes and mass or 1 dispersal mode and mass) are summed to determine the overall winner.
A worksheet with analysis questions is completed by students in class or at home for activity
wrap-up. Students are also asked to create graphs of seed mass vs. dispersal performance.
Appendix: Sample Worksheets
Seed Dispersal and Design Worksheets
Activity 1: Seed Dispersal
Seed Dispersal – Part 1
1. What is a seed?
2. How might the seeds of invasive plants be different than many native plants?
3. What are the ways that seeds are dispersed?
4. Do you think it is better to have lots of small seeds or a few large seeds? Why?
Group Activity Instructions:
·
·
·
·
Examine each of the seeds and describe them in the table.
Develop a hypothesis about how each seed is dispersed based upon the appearance of the seed.
Test each seed using the tools provided.
Report to the class your group’s findings. Discuss dispersal strategies.
Seed Name
Observations
Hypothesis
Draw and/or describe seed.
How do you think it is dispersed? Why?
1.
2.
3.
Seed Name
Air
Wind/Loft: fan
Resistance/Gravity: distance (cm)
height/time (cm/sec)
Stickiness: fabric
and fur (test for 60
seconds)
Water/Float: time
(check for 60
seconds)
1.
2.
3.
4.
5. Did the tests support your hypotheses?
6. Do any of the seeds do well at more than one dispersal method? Why might this be a useful strategy?
7. Do the seed dispersal strategies of invasive plants make them more successful? How?
Most successful dispersal
method
Seed Dispersal and Design Worksheets
Activity 2: Design-a-Seed
Group members:
Class period:
Seed Design Worksheet
1) What dispersal vector or vectors will your seed disperse by (air, wind on the ground, animal)?
2) List 2 features that would help a seed disperse by this vector.
1)
2)
3) What materials will you use to make a seed that can disperse by this vector?
3) List two ideas for maximizing seed mass while allowing your seed to disperse well.
1)
2)
6) Sketch and label a diagram of your group’s seed design.
Do not begin building your seed until your diagram has been approved by your teacher!
Name:
Class Period:
Seed Competition Data
Seed ID
Mass (g)
Drop
time 1 (s)
Drop
time 2 (s)
Fan
distance
1 (m)
Fan
distance
2 (m)
Animal
cling
time 1 (s)
Animal
cling
time 2 (s)
Name:
Class Period:
Seed Design Analysis
1) On a sheet of graph paper, graph one of the following:
-Seed size vs. drop time
-Seed size vs. fan distance
-Seed size vs. animal cling time
Be sure to give your title a graph, label axes and units, and label data points with seed ID
2) Is there a relationship between the dispersal parameter and seed size in your graph? Describe
the trend of your graph in 1 complete sentence.
3) Circle the data point representing the winning seed in this category on your graph. This is the
seed that has the best probability of survival. Was it the biggest seed? Did it have the best time
or distance? Describe in 1 complete sentence where the winning seed is on your graph in
relation to other data points.
4) Based on your graphed results, how should a plant spend more energy making seeds larger or
giving them special features for dispersal? Why? Your answer should have at least 2
complete sentences.