Goals:

1) Experience statistics as it is practiced in biological research:

2) Develop a systematic model for development of an experimental design.

Materials:

• Seeds need to be purchased weeks in advance.
• Lab space and materials such as Petri dishes or plastic bags for seeds, pipetters, liquid smoke.
• Other materials may be needed depending on student design.

Seed Germination Lab: Printable Student Version

Instructors Notes:

Prerequisites: Students should have read and answered questions from the ANOVA: Factorial Designs tutorial before Day 2, designing an experiment. While not necessary, reading the ANOVA: Advanced Design tutorial would also be very beneficial.

Paper Review: I have found that some students are initially frustrated or intimidated when they are asked to read a research paper outside of their major. In my experience, providing more time to read the paper has not been helpful, however, it may be appropriate to:

• clarify that the paper review questions are worth only a small amount of the overall grade
• allow students to complete the assignment in groups
• allow students to turn in a revised version of their paper review questions after they are discussed in class

Class Discussion: I suggest spending at least part of three separate class periods to discuss the Keeley paper and develop a class project.

Day 1: Spend at least 20 minutes discussing the paper review questions. Also start students thinking about designing their own experiment. Student my not feel qualified to design a biological study. You many want to help identify other questions that could be developed from Keeley’s paper, such as:

• Are all stimulated species in the chaparral region affected by liquid smoke in the same way?
• Fire is an integral part of the prairie species ecosystem. Do these species respond in the same way as chaparral species?
• Does heat and nitrogenous compounds interact?
• Are there optimum heat or nitrogen levels for some species that promote germination?

How would you design a test to answer these questions? Which factors and what levels could be used? Which questions relate to main effects and which relate to interaction effects? How can you design an experiment that is general enough to be of scientific interest, but specific enough that it can be conducted within a lab in a few weeks time?

Day 2: Invite a biologist or ecologist to the class (or a statistician if you are a biologist) to answer student questions that are beyond your scope of knowledge.
It was very helpful for my students to hear from a researcher in ecology that he did not know all the answers to their questions.
My students seemed to be somewhat surprised that they could contribute to science by conducting an experiment that has never been specifically studied before. Having a biologist enforce the idea that science in not just a collection of facts but an ongoing exploratory process was very helpful for my students.
The ecologist was also very helpful in giving suggestions on which levels and factors are appropriate to test. For example, some species of seeds are more appropriate to use in a classroom experiment, which temperatures best reflect the appropriate heat from fire stimulation, etc…

Day 3: After students have submitted their experimental ideas, the class voted on one experiment to conduct as an entire class. This allowed us to test more factors and levels with replicates in less time.

Grading: I would suggest 50 points for the entire project (this is the same value as an exam in my course).

• 5 points for Day1, the Keeley review
• 10 points for Day 2, experimental design
• 5 points for lab procedures
• 5 points for appropriate comments and suggestions on other student papers
• 25 points for the final paper

Designing an Experiment:
For professional biologists studying fire-stimulated germination, priority in the selection of species used in an experiment depends on significant open questions in the research field. In the classroom, convenience matters, too. Suitable species for this exercise are ones whose native environments experience (or once experienced) frequent fire (e.g., California chaparral plants, tallgrass prairie plants from the Midwest), whose seeds are readily available commercially or can be easily and legally collected, and whose seeds germinate within a few weeks—when they do germinate—without special treatments besides fire-related ones (e.g., cold-treatment, simulating winter). Some California species that meet these conditions are Phacelia minor and Salvia columbariae (chia, not to be confused with domesticated chia, S. hispanica), which are available at California native plant nurseries (http://www.larnerseeds.com/, http://www.theodorepayne.org). See Baskin and Baskin (1998) for other suitable species. 

KNO3 can also be used to represent the nitrogenous compounds found in the soil after a fire. Thanos and Rundel’s (1995) suggested concentrations of 0mM to 15mM.

Coleman and Montgomery (Technometrics 1993) present a discussion of methodology and some guide sheets useful in the planning phases of designing and conducting an industrial experiment.

Stat2labs was developed with partial support provided by the Transforming Undergraduate Education in Science (TUES).program at the National Science Foundation under DUE 0510392 and DUE #1043814