Summary
In this lesson, students will explore a variety of plant reproductive structures and determine differences between sexual and asexual reproduction through hands-on observations and online research. Based on their findings, students will use engineering design to create and test "seed dispersal" structures. After testing and revising their designs, students will use data from their tests and previous investigations to defend the scientific merit and biological relevance of their structures. This lesson addresses MS-LS1-5. (Funding provided by USDA Project No. 2015-08433 through the National Institute for Food and Agriculture's Agriculture and Food Research Initiative.)
Essential Question(s)
How do specialized structures affect a plant's likelihood of successful reproduction?
Snapshot
Engage
Students observe the phenomenon of exploding seed pods to generate questions about types of plant seed dispersal mechanisms and their purpose.
Explore
In small groups, students investigate the reproductive strategies of a model fruit or seed. Groups share out their findings visually to the class to create a data set for later reference.
Explain
Students compare and contrast their individual model plants. From the Explore data and Explain discussions, the whole class synthesizes a list of the most important scientific concepts.
Extend
Students design artificial plant structures for seed dispersal and test the effectiveness of their devices. The class engages in a bracket-style challenge to determine the most effective device and discusses why there is still no "best" design.
Evaluate
Using their investigative and design test data, students make a pitch to a company arguing for the merits and scientific relevance of both their design and the seed pod phenomenon.
Materials
Lesson Slides (attached)
I Notice, I Wonder handouts (attached, one per student)
Assorted fruits and seeds
Research Notes handout (attached, one per group of 3-4 students)
Assorted recyclable materials (for building seed prototypes)
Model Plant Design handout (attached, one per pair of students)
Model Self-Evaluation handout (attached, one per pair of students)
Bracket Graphic Organizer (attached, one per pair of students)
Artificial Seed Dispersal Pitch Planning Document (attached, one per pair of students)
Devices with video recording capability or poster materials (optional)
Student devices with Internet access
Engage
Begin the lesson by displaying slide 3 and passing out a copy of the I Notice, I Wonder handout to each student. Show students the example of exploding seed pods, and have them make observations and ask questions about what they see using the I Notice, I Wonder prompts. Encourage them to think about why this phenomenon might happen and what purpose it might serve. After giving students some time to record their individual responses, ask for volunteers to share out and record class responses on the board.
Display slide 4. Review the questions that the class generated for the "I Wonder" prompt and help students select one or more to continue investigating. Students will probably wonder how the phenomenon works. Encourage them to explore that during their upcoming investigation to find out for themselves.
Explore
Display slide 5 and organize students into groups of three or four. Give each group a copy of the Research Notes handout as well as a unique plant so that the class has examples of a variety of seed dispersal strategies.
Allow students time to investigate their plants as well as the research questions they chose during the Engage activity. Students should investigate:
Their research questions.
Their plant's life history (e.g., what it is, where it can be found, etc.).
Their plant's reproductive strategy (i.e., sexual, asexual, or both).
How their plant passes on its genetic information (e.g., seeds, runners, etc.).
The purpose of their plant's external structures (e.g., Why does a dandelion have "fuzz" after the flower dies?).
Display slide 6. Now that groups have an understanding of their plant, they will prepare a visual presentation to share their findings with the class. Posters, whiteboard art, and digital slides are some options for this presentation. Feel free to customize this slide with specific guidelines. In their presentations, ask students to share the life history and reproduction information that they investigated but wait to cover the research questions until later.
As each group shares its presentations with the class, instruct students from the non-presenting group to record the data about reproduction, seeds/runners, and external structures on the second page of their Research Notes handout.
Explain
Display slide 8. Have students form new groups where they will discuss the questions on slides 9-11.
Slide 9:
How does your plant pass on its genetic information (e.g., seed, runners)?
How does your plant disperse seeds?
If your plant does not disperse seeds, how does it reproduce?
Slide 10:
How do the patterns you notice in the dispersal strategies used in asexually reproductive plants compare to those that are used in sexually reproductive plants?
Why might those patterns exist?
Slide 11:
Why would plants need to disperse their seeds?
What are the costs and benefits of dispersing seeds near the parent plant? Far away from the parent?
Display slide 12. Have students return to their original research groups. Use the Strike Out strategy to help students develop a list of important scientific ideas they learned from their exploration and discussion. Have students start by working with their group to write down as many important scientific ideas as they can from their research and discussion.
Display slide 13. Have groups pass their list to the group next to them. (Choose a specific direction (left, right, etc.) to avoid confusion.) When groups receive their peers' list, they should cross off one item that they feel is least relevant or least important. Repeat this step for as many groups as you have in class, time permitting. (Make sure the lists go through at least three new groups if there isn’t time for every group to evaluate every list.)
Display slide 14. Have groups return the lists to their original owners. When groups receive their own lists, back, instruct them to choose one of the crossed-out items to add back to their lists. Then, have them look at the items and consider if any could be grouped together into larger categories.
Display slide 15. Have each group share out their lists of ideas and record them as a master list. This represents the ideas the class thinks are the most important. Discuss any items that might be able to be combined. At this point, if students missed any of the important concepts referenced in the previous discussion questions, facilitate additional whole-class discussion to solicit those ideas. If there are additional concepts specific to the example plants that students did not pick up on in their research, this is the time to provide direct instruction or supplemental readings.
Extend
Display slide 16 and pass out copies of the Model Plant Design handout. In pairs, students will create a model plant or plant part designed to disperse seeds based on the essential question: How do specialized structures affect the plant's likelihood of successful reproduction? Based on the scientific concepts developed in the Explain activity and the firsthand exploration of actual plant structures, pairs will 1) prototype their models, 2) build their models using recycled/recycling materials and test them, 3) evaluate their models' effectiveness, and 4) revise their models. This procedure is described in detail below and on slides 17-27.
Display slide 23 and pass out a copy of the Bracket Graphic Organizer to each pair. Have pairs write their team name or design name in the top box in the first column of the bracket and then find another pair to match up with. Display slide 24. Have pairs write the opposing pair's name below theirs in the bracket. Then, pairs should compare and contrast the design, strengths, and weaknesses of their two models, record their observations, and determine, based on the data, which was more effective at seed dispersal. They should write this team name in the second column.
Display slide 25. Have the groups of four pair up to create groups of eight. In this large group, students will compare the two designs that were selected as more effective in the previous round. Again, they should compare and contrast the design, strengths, and weaknesses of the two models. Based on the data, they should determine which was more effective and write this team name in the third column.
Depending on your class size, you'll generally have 2-4 models remaining at the end of three rounds. Engage in a whole-class discussion to compare the design features, strengths, and weaknesses of these models and decide on one that is most effective. As part of this discussion, be sure to emphasize that as long as the device they created was able to disperse seeds, it was successful, even if it was not the most effective at the task. Guide students to understand the difference between being the most effective versus being "the best" design.
Display slide 26. Through discussion, help students compare similarities across designs, strengths among them that the "most effective" does not address, and weaknesses of the "most effective" that other designs account for or solve (if applicable). Guiding questions for this discussion might include:
What patterns in the data support the conclusion that plant structures affect the probability of reproduction?
How might the distance that seeds are dispersed affect a plant's reproductive rate?
How did your designed structure make it more or less effective at distributing seeds?
Which other designs had similar characteristics? Why might two designs with similar strengths or structures not perform the same?
What are some strengths of the other designs that the most effective did not have? How do those other designs improve upon the weaknesses we identified in the most effective?
If all of the models performed equally effectively, how could we decide which is "the best"? (Press students here to point out that the designs are different but not better or worse than one another.)
If any devices were unable to disperse seeds, frame the discussion in terms of the design being a rough draft and as an opportunity rather than a deficit. (For example, "If this was a real plant, what would be the effect if it couldn't disperse its seeds?") This discussion will provide an excellent segue into the final portion of the Extend activity. Emphasize for students that engineering design involves improving designs before the final version is built and used.
Evaluate
Display slide 29. Pass out a copy of the Artificial Seed Dispersal Pitch Planning Document to each pair of students and introduce the scenario presented on the slide:
A company is developing artificial plants to support the reproduction of endangered species. The company wants to mimic actual seed dispersal and has asked for design ideas for structures with potential for use in this work. You have identified two possible structures, the exploding seed pod you saw earlier and the device you designed in class. Create a sales pitch for the company to argue the merits of each.
Give students time to create a pitch that they will present (as a poster, oral presentation, written proposal, video, etc.) arguing in favor of designs based on their effectiveness and scientific relevance. Student pitches should be evidence-based arguments that highlight the purpose of structures in both the exploding seed pod from the Engage section and their own designs from the Extend activity. The pitches for each example should also explain the effect of the dispersal mechanism (i.e., seeds carried away from the parent plant) and why this effect is important (i.e., how it helps the plant reproduce). Use slide 30 to outline any specific pitch and presentation guidelines that you might have.
When students are finished working, have them present their pitches to the class and turn them in as an assessment for the lesson.
Resources
A Bit of Botany. (n.d.). Dispersal of seeds by water. http://theseedsite.co.uk/sdwater.html
Armstrong, W.P. (1999). Blowing in the wind: Seeds & fruits dispersed by wind. http://www2.palomar.edu/users/warmstrong/plfeb99.htm
Armstrong, W.P. (1998). Ultimate and painful hitchhikers. http://www2.palomar.edu/users/warmstrong/plmay98.htm
Gardener Scott. (2012, July 29). How to propagate strawberries [Web log comment]. http://gardenerscott.com/gardenerscott-blog/how-to-propagate-strawberries
Hillmann, R. (2013). Seed heads are not weeds! Lawn-A-Mat Lawn Care. https://web.archive.org/web/20160412003802/http:/lawnamat.net/seed-heads-are-not-weeds/
K20 Center. (n.d.). I notice, I wonder. Strategies. https://learn.k20center.ou.edu/strategy/d9908066f654727934df7bf4f507d1a7
K20 Center. (n.d.). Inverted pyramid. Strategies. https://learn.k20center.ou.edu/strategy/d9908066f654727934df7bf4f507a918
K20 Center. (n.d.). Strike out. Strategies. https://learn.k20center.ou.edu/strategy/d9908066f654727934df7bf4f5062cdf
NGSS Phenomena. (2019). Phenomena for NGSS: Creating the next generation of student engagement. https://www.ngssphenomena.com/#/exploding-seeds/
Sanders, R. (2015, March 26). Why conifer seeds twirl with one 'wing.' http://www.futurity.org/conifers-trees-seeds-884072
Wikipedia. (2020, March 14). Impatiens capensis. Retrieved 2020, June 11 from https://en.wikipedia.org/wiki/Impatiens_capensis