Instructions

Class Period One: Designing Labs

Note: you can prepare the lab stations yourself or assign a few students to set up and “man” each station.

1) Blend two handfuls of lettuce leaves with 1-3 cups of water until little or no plant material is visible. Pour into spray bottle. Repeat with strawberry guava leaves. Fill one spray bottle with plain water. Label spray bottles.

Cut paper towels into circles that fit inside the Petri dishes. Print out Copy Master “Station Instructions.” Cut into sections and place each instruction at its appropriate station.

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2) Set up five stations for students to visit in order.

• Station #1: Petri dishes, paper towel circles, labels, and indelible markers
• Station #2: Lettuce seeds (10 seeds per dish)
• Station #3: 3 spray bottles – one filled with water, one with strawberry guava mixture, and one with lettuce mixture
• Station #4: Student Page “Ecosystem Engineers”
• Station #5: Student Pages “Ecosystem Engineers Lab Report” and “Daily Data Sheet” (one each per group)

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3) Lead a discussion on the scientific method, using Teacher Background “Scientific Method Chart.”

Question: What are the steps of the scientific method?
Answer: The scientific method begins when you 1) ask a general question and 2) conduct some background research. Next, you 3) develop a hypothesis and 4) test the hypothesis in a controlled experiment. 5) Collect and analyze results. 6) Determine whether your hypothesis is true or false, based on your results. 7) Report your results and conclusion. If your hypothesis is false, you can begin the process again with a different hypothesis.

Writing a hypothesis as an “if… then” statement is a prediction of the results you need to support the hypothesis.

For example: If strawberry guava compounds stifle plant growth, then seeds receiving the compounds should grow 20 percent shorter than the control.

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4) Tell students that they will be replicating the 2010 experiment of a University of Hawai’i student, Kelly Bongolan. Explain that scientists repeat one other’s experiments in order to verify results. When the same results can be demonstrated time after time, a hypothesis moves from a guess to
an accepted scientific fact.

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5) Break the students into groups of 2-3 and have them visit each station.

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6) Arrange Petri dishes under a window or light table. Each group will spray their Petri dishes every day for two weeks, using the appropriate spray bottle for each dish. (Assign students to take their groups’ dishes home over weekends.) They will record data for each Petri dish (control, lettuce and strawberry guava) on their Student Page “Daily Data Sheet.” After the seedlings sprout, students will record the total number of sprouted seedlings, the root length of the two largest seedlings in each dish and the shoot length of the two largest seedlings in each dish.

Dishes need to remain moist. Depending on the classroom climate, they may need to be sprayed more than once a day. Also, consider refrigerating your spray mixtures, or mix fresh batches every few days.

Class Period Two: Analyzing and Reporting on Results

1) After two weeks, collect the completed Student Page “Daily Data Sheet” from each group. Summarize the entire class’s data in charts and graphs. These charts and graphs can be drawn on graph paper or created as computer spreadsheets. Discuss why scientists calculate their results in a variety of ways, ie: using mean number and median.

For example, have students calculate the mean number of days it took seeds to germinate for the control and each of the variables. Determine the median days to germination and display in a table. Do the same for seedling growth. (You can compare the class’s results to those collected by University of Hawai’i student Kelly Bongolan. Her poster is included in the Teacher Background.)

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2) Hand out the “Lab Report Guidelines” worksheet and review it with the students. Have students complete their “Ecosystem Engineers Lab Report” based on the data gathered by the entire class.

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3) The students will then make a poster out of their experiment to put on display for the class. The poster should include their hypothesis, a brief version of the procedure, and the results, including the graphs they made.

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4) Place the posters on display in the classroom. Students can do a gallery walk, providing constructive and positive comments about each poster by writing it on a sticky note and placing it on the poster.

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5) Have students turn in their “Ecosystem Engineers Lab Report.”