Download Yucca Mystery - City of Fort Collins

The Yucca Mystery* 2012
Grade Level: Intermediate
Setting: prairie, field trip (a site with yucca plants, off-trail site if possible)
Conceptual Framework: Interconnection
Description: Students unravel a mystery to learn about a mutualistic relationship on the
shortgrass prairie.
Theme: The prairie is special because it is full of mystery.
Time- 45 minutes
Recommended Group Size: up to 26 students
Standards: Life Science 2.3 Explain and illustrate with examples how living systems interact
with the biotic and abiotic environment. There is interaction and interdependence between and
among living and nonliving components of ecosystems.
FOSS Kit: Environments
Materials list:
• Map showing Canadian populations of Yucca glauca.
• Several samples of yucca pods with seeds from resource room
• Yucca background information packet for naturalists
• Detective’s Notebook worksheet, pencils, clipboards (one per student)
• Chart paper and markers (with blank KWL chart)
• Picture of Milk River, yucca moth, yucca flowers
• 13 clues, laminated, in envelope
• Mystery bag with yucca objects (soap, tums, asprin, thread, needle, basket, yellow red
and white markers, card with the word FOOD).
Getting Ready:
• Familiarize yourself with the yucca background information for naturalists.
• Gather materials
• Find a spot for the lesson with several yucca plants nearby
Procedure:
1. Introduce yourself and ask students if they can solve a few riddles with you…
a. What is tall and wears many rings? (a tree!)
b. What is the meanest flower? (a snapdragon!)
c. Why are trees so noisy? (they all bark)
d. What plant is the funniest? (The yucca!)
Ask, why are riddles so funny, its because they are little mysteries and its fun to solve mysteries.
Based on the riddles, what do students think the activity today is going to be about? Hopefully
students guess something about plants. Do they know any plant riddles themselves? Share
them. Tell students the prairie is special because it is full of mystery/riddles (this is the theme of
the program).
2. Bring out the mystery bag. Tell students that all the objects inside have something in
common. Lay out the objects in the bag, soap, tums, asprin, thread, needle, basket,
yellow red and white markers, card with the word FOOD. Give students some time to
look the objects over and make some guesses.
3. Ask them if they have heard of a yucca plant- the one from the riddle- it’s a real plant! It
was no laughing matter to Native Americans and pioneers! Point a yucca out and explain
to students that this is a very important plant for people. Explain the mystery bag objects
connection to yucca. Indians and Euro-American pioneers derived an effective soap from
its root. Thus another common name for yucca is soapweed. (soap) Medicinally, the root
was used to treat upset stomach (tums), arthritis, inflammation from bruises, sprains, and
bone fractures (asprin), and to reduce hair loss. Today, herbalists use it as an antiinflammatory. The flowers, flower stalks, and seed pods are edible if properly cooked
(food). Additionally Indian peoples pounded the hard leaves to loosen the fibers, which
were twisted into thread (thread), the sharp point serving as a needle (needle). Bleached,
sun-dried yucca leaves (from the Arizona species Yucca elata) are used for white coils in
Papago Indian baskets. Greenish-yellow designs come from unbleached yucca leaves,
while red patterns are produced by a natural dye from yucca roots (markers).
4. (Somewhere within sight of a yucca plant.) tell students it turns out that this very
important plant needs your help! You are glad they are here because we have an
important mystery to solve today involving the yucca. Ask students what they know
(other than the human uses you just explained) about yucca plants. If it is not much, tell
them its okay, because as they solve the mystery, they are going to learn many MORE
amazing and wonderful things about yucca!
5. Ask students, did you know that yuccas can live as far north as Canada? There are two
populations of yucca glauca, the same yucca that is here in Colorado in southern Canada
(show map). These populations of yucca are special, because they are so far north.
There is great concern about one of the populations of yuccas- the Milk River population,
in Alberta, Canada (show picture of Milk River). The reason people are concerned is that
the plants have not produced any seeds for at least 5 years. Pause and ask students why
are seeds important? Without seeds, how are the yucca going to survive? Without seeds,
no new plants will be growing. Eventually the existing plants will grow old and die and
the yuccas will be gone from Milk River. That would be a tragedy! Maybe you can help
solve this riddle.
a. Your job is to solve the riddle/ mystery! We are going to find out why aren’t the
yucca plants in Milk River making seeds. That is the mystery/ riddle for today.
You are here, at ____ Natural Area because we hope that by investigating a
healthy population of yuccas, you can determine what is different between the
two places. Today you’ll be learning about the yucca plant, looking at yucca up
close and learning about the yuccas in Milk River, Canada. You’ll need all your
best detective skills… your observation skills, your brilliant mind, and your heart
too- are you ready? Do you want to help?
b. Ask, what do students think might be going on? What kind of information will
they need to solve the mystery? Make a KWL chart (one column for what is
Known, one column for what students Want to learn and one for what students
Learned at the end). Reassure students that they will get all the clues they need to
solve the mystery.
6. First let students investigate a yucca plant- give them a few minutes to observe and gather
clues- send groups of 3-4 students to yucca plants. Have them record their observations
on the worksheet- what does the yucca feel like, smell like, look like?
7. Now that students have a general idea what a yucca is like, ask them to search for
evidence about how yucca plants make seeds/ reproduce. Guide them towards looking at
the seed pods (if present). Point out that the seed pods are the place seeds are kept and
that this must be an important clue because the yuccas in Canada are not making seeds.
Ask students to form a circle while still standing next to a yucca plant (if possible at your
site, if not see #5 below). Ask each group to share an observation about their plant- the
other groups respond by raising their hand if their plant has that same characteristic. Go
around the circle until students have looked closely and noted many things about the
yuccas. If possible guide students to look at the seed pods and possibly notice the small
hole made by the yucca moth. Encourage any responses that focus on the seeds,
reproduction.
8. If encircling the yuccas is not possible, gather students and ask them to share their
observations- record their findings in the L section of the KWL chart. Then hand out a
clue- a sample of a yucca seed pod with seeds inside. Let students investigate and ask
questions. Once they have looked over the pod for a few minutes, repeat the circle
sharing activity in #4, above.
9. Tell students they will each get a clue about this mystery and their job is to put the clues
in the right order. Break students into pairs. They should read their clue to their partner,
and then walk around to other groups and try to put the clues in order.
Correct order of clues…. (There are 13 clues for 26 students)
1. Every spring, the yucca blooms.
2. The yucca moths find an open flower and mate there.
3. After mating, the female moth crawls from flower to flower and flies from plant
to plant. At each flower she gathers some pollen and rolls it into a ball.
4. The pollen ball gets so big that if the yucca moth adds anymore she won’t be able
to fly to the next plant.
5. Because she can’t carry the pollen ball anymore, the yucca moth finds the center
of the flower, puts the pollen ball there.
6. The pollen ball pollinates the plant’s “eggs” now the pollinated “plant eggs” will
become seeds.
7. After the yucca moth has pollinated the flower, she lays her eggs in the same
place as the developing seeds.
8. After laying all her eggs, the yucca moth dies.
9. While the yucca seeds are developing, the yucca moth eggs hatch into larvae.
10. The yucca makes enough seeds to make more yucca plants and to feed the
hatching yucca moth larvae.
11. The yucca moth larvae eat the developing yucca seeds and then chew their way
out of the fruit and drop to the ground.
12. The yucca moth larvae burrow into the soil and make a cocoon.
13. When the yucca is in flower, the yucca moths emerge from their cocoons.
* If you have fewer than 26 students, some clues can be combined (ie 1 and 2, 7 and
8, 11 and 12).
10. As students read their clues out loud, provide supplemental details and photos to support
each step (see background information). Ask, “How do we know the yucca moth was
here?” Be sure to highlight the fact that you know moths are present if the small hole on
the seed pod is present.
11. Students now have a chance to ask questions about the Canadian population of Yucca.
Have them work with their partner or group to formulate a question and then take one
question per group in the circle style used above. Refer to the KWL chart. If students
need help coming up with questions encourage them to ask what is the same and different
about the Canadian population. Use the KWL chart to point out what is unique to the
natural area, the same about both populations and unique to the Milk River population.
12. If needed, give students another clue- a photo or sample of a seed pod WITHOUT the
small hole from the moth. Ask them what is different about this seed pod from the ones
they have been investigating? Tell them that where yucca moths are absent, yuccas will
not produce seeds unless they are hand pollinated. Answer questions until students
discover that yucca moths are not present in the Milk River population. Guide them
towards the answer as time and maturity of students indicates. Try using same/different
comparisons or have the students ask you true/false questions. Lead students towards the
conclusion, no hole= no moth=no pollination= no seeds.
13. Marvel in the fact that the yucca and the yucca moth have developed this special
relationship over time. Explain to students that this type of relationship is called
mutualism. It is when two organisms depend on each other for survival and both benefit.
Conclusion: Tell students- see how fun it was to solve a prairie riddle/ mystery? What did you
do that helped you solve the mystery? (good observation skills, listened carefully for clues,
thought about how things might relate to each other). You did a great job! It turns out that the
natural world is full of mysteries like this! Even the smallest relationship between a bug and a
flower is important and interesting! The more you learn about the prairie, the more fascinating
things you’ll learn. Reiterate the theme, “the prairie is special because it is full of mystery.”
Encourage students to keep learning about the prairie and discovering mysteries and finding
solutions! Oh by the way, one more riddle- How did the yucca moth know how to get out? She
“seed” the way!
This lesson was written by Dolores Daniels and Zoe Shark of the City of Fort Collins Master
Naturalist Department.