Challenges to Anticipate and Solve:
- equipment availability: Students want to collect all kinds of data from this experimental plot. Much of it involves abiotic variables. The
challenge is to come up with equipment to allow this data collection and to get students to collect data for which you have equipment.
My strategy for this is both short and long term. In the short term, I require students to think about why they wish to collect any given
data. This often leads them to realize they do not need that data. If they still feel they need this data and we do not have the equipment,
I simply tell them that. If this data is important for the research they are proposing, I suggest they include this data collection as an
experiment in their proposal. In the long run, I will purchase useful equipment that is not yet available in my department.
A variety of equipment is easy to make, acquire, or purchase inexpensively. Equipment for quadrat, point, and line transect sampling of
vegetation is easy to obtain or build. For example, 1 m2 quadrats can be built with 4 lengths of PVC pipe and 4-90o
PVC corners. Larger quadrats for sampling larger scales (e.g. trees and shrubs) can be constructed with 4 stakes and string. Soil test
kits for estimation of soil nitrogen, phosphorus, potassium, and pH are readily available from many sources (e.g. Hach, LaMotte, and local
garden suppliers) and not expensive. Simple methods to visualize and estimate stomata density are found in
Grant and Vatnick 2004 (TIEE Vol 1 - tiee.ecoed.net/v1/experiments/stomata/stomata.html).
Although large scale destructive sampling is not appropriate in our experimental plot, students could selectively sample plants to develop
allometric estimates of plant biomass (see Griffith and Forseth 2003)
Students interested in ecophysiology may be out of luck due to the cost of equipment. Light meters and sensors for photosynthetically
active radiation (PAR) are available from about $500 to $1000. Be sure to purchase a sensor that measure in units that can be related to photosynthesis
(e.g. µmol · m-2 · s-1). Portable photosynthesis, gas exchange, and water relations measurement equipment like the
LiCor 6400 costs about $10,000. Leaf area meters may cost from $2500 to $5000, but leaf area can be estimated using leaf sketches
on graph paper.
- formulating questions: Many students struggle with formulating specific questions for their proposals. Students must propose questions
with specific measurable dependent and independent variables. The challenge of the instructor is to provide support in this difficult and
many times first time task, but not to tell students what questions to ask. I ask students what their dependent and independent variables
are and if they are measurable. I also stress that there should be some relationship among their questions to create an integrated research
proposal. It is this relationship among research questions that creates a broader context for the proposed research. In developing their
research agenda, students may work from the specific questions to the broader conceptual questions or they may work from the broad
concepts to the specific questions. I do not yet know which direction is preferable pedagogically.
To date for my course, the ecological questions addressed by my student groups have generally concerned
spatial and temporal patterns in plant population and community ecology. The broad concepts covered include mutualism
and potential mechanisms of that mutualism, life history differences among grasses and forbs, seed germination strategies,
competition and specific limiting factors leading to competition, environmental correlates of species diversity, and root competition.
Here are 4 sets of questions showing a range of ecological concepts addressed. The broad concepts covered include mutualism and
potential mechanisms of that mutualism, life history differences among grasses and forbs, seed germination strategies, competition and
specific limiting factors leading to competition, environmental correlates of species diversity, and root competition. Although all of these
hypotheses deal with spatial ecology, students should be able to address hypotheses / questions about changes in time, if they have an
historical dataset of plant abundance and distribution from the experimental plot.
a) Does Amaranthus sp. have a mutualistic relationship with Digitaria sp.? Does Digitaria sp. grow taller when growing close to
Amaranthus sp.? Does Amaranthus sp. decrease wind speeds around its stems? Does Digitaria sp. grow more densely when
growing close to Amaranthus sp.?
b) Do grasses germinate earlier in the summer than plants with broad leaves and short stature (i.e. forbs)? Do forbs germinate
better under low light conditions than thin leaved, tall plants (grasses)? Do forbs increase stem length more quickly in low light
conditions than in high light conditions? For grasses that germinate in open canopies, does high light intensity increase
phytochrome activity in the seeds?
c) Does Oxalis sp. (wood sorrel) grow in lower abundance when growing in the presence of other plant species than when
growing in the presence of other Oxalis sp. plants? Does Oxalis sp. grow in lower abundance when growing in low light levels?
Does Oxalis sp. have lower stomatal apertures to increase CO2 uptake in low light levels? Does Oxalis sp. grow in lower
abundance when growing in low soil nitrogen levels?
d) Does species richness increase with increased incident light levels? Does species richness increase with increased soil
moisture levels? Does total biomass of plants increase when fibrous root plants and tap root plants grow together, as
compared to when fibrous root plants grow with fibrous root plants or tap root plants grow with tap root plants? Do fibrous
root plants uptake soil nitrogen from more shallow soil depths than tap root plants?
- experimental plot: While my experimental plot was off campus, this may or may not be a challenge for some departments. Some schools
do not provide transportation resources. In this case, any appropriately sized plot of vegetated land on campus will do for motivation. For
example, the faculty of Cedar Crest College, Allentown, PA maintain a research plot on campus which is a small piece of land that has not
been mown for many years. The faculty have kept a time series of data from ongoing sampling of the plot. Alternatively, most grassy lawns
are not monocultures and so contain considerable diversity. This surprising amount of diversity leads to interesting questions. For example,
given the strict and routine management of lawns, how do we explain the distribution and abundance of plant species on these lawns?
- working in groups: At the University of Mary Washington there is an explicit honor code that reads, in short, as follows, “I hereby declare,
upon my word of honor, that I have neither given nor received unauthorized help on this work.” Students raise many questions about what
work can be done as a group and what must be produced individually. The instructor needs to be clear from the onset about these group vs.
individual issues. I will give two examples of the differences between group and individual work. First, data from the experimental garden
(e.g. plant abundance, plant distribution, maps of rare plants, soil moistures, and soil textures) has been collected by different groups in the
class. This is simply an efficient way of collecting data useful to the whole class. For example, if there are 6 groups in the class, the
experimental garden can be split into six smaller sections for each group to sample plant abundance. This data must, in turn, be shared among
all six groups. Once the data is shared each individual should have a copy of all data collected by each group for their use. Each individual
should create appropriate data presentations and write titles and captions for the presentations. It may be difficult or impossible to verify that
each student has created his/her own graphs and tables. I would say though that you can expect significant differences among the titles and
captions of graphs and tables when you assess their data presentations. Second, annotated bibliographies are assessed individually, but they
emerge from the work of the group. I believe it is sensible and efficient for the members of a group to share their literature search efforts. This
shared effort has several purposes. Students will have different levels of experience with literature searches. Thus, the group can work together
and learn from each other. At UMW, the whole class works in our “Science Literacy Center,” a dedicated computer room in the science building.
Each student can do literature searches at his/her own computer and work side-by-side with peers. The group can also share ideas about the
appropriateness of papers as they find them. I have also allowed students to share the task of typing and formatting references. The task of writing
reference annotations after reading papers is an individual task.
In addition, group work invariably leads to personality conflicts in one or two groups. To a certain extent, I believe students should be encouraged
to work out these conflicts among themselves. These people will likely work in teams during their careers and will run into the same kinds of
conflicts in the future.
Another group issue that may arise is whether or not all members of the group contribute equally. This is a difficult matter to track and I have not
yet developed consistent measures to evaluate this equity issue. First, keep your eyes and ears open. As you work with and ask questions of
research groups, note who answers questions and who does not. Challenge quiet students to respond to your questions as you interact with
groups. You may have to explicitly ask more verbal students to remain silent. Ask individuals in a group about any tension you sense among
members of the group. Second, carefully compare individual assignments among the individuals of each research group. Assignments like the
annotated bibliography are sufficiently complex that there should be little similarity among individuals in a group. Third, ask students about their
group’s dynamics and division of labor. Have they shared resources while gathering references for their research? Has each member contributed
equitably to the organization and creation of oral presentations? The discussion on Formative Evaluation in the Teaching Section of this website
provides some guidance on how to ask students to evaluate their performance and their peers’ performance in the group.
- in-class and out-of-class time commitment: The experiment schedule as presented in the class syllabus
(see syllabus_fall2003.doc, 36kb)
does not use laboratory class time as efficiently as is possible. The experiment is currently designed to have a significant amount of in-class
time devoted to work such as library research, oral presentation development, and peer reviews of proposals. This decreases the amount of time
that one might expect from students out of class. As I refine the details of this experiment, some of this in-class time will be reorganized.
When I move some of this in-class work to out-of-class work, I anticipate inserting short term exercises during laboratory class time to supplement
lecture concepts, computer modeling exercises, and / or discussions of research articles.
Comments On the Lab Description:
Introducing the Lab to Your Students.
Before going to the field site for this experiment, the students receive the introductory handout for this experiment. They have already received
the course syllabus, which lists the assignments for the laboratory portion of the course. The handout includes the goals for this experiment,
some background on the context of this experiment, and the objectives of the first laboratory. I verbally describe the assignments that will be
due for their laboratory work. I also verbally describe the handout and briefly describe the process we will follow to produce the final assignment:
a written research proposal. This places their assignments in the context of the work for this experiment. The remainder of the first laboratory
is conducted at the Gari Melchers Estate, the site of the experimental plot. The head gardener and grounds manager of the estate gives a brief
history of the grounds of the estate. She also gives a brief description and history of a prairie grassland plot she has developed over several
years. This is significant because the same prairie species were seeded into the class’ experimental plot. I then describe to the students
how the experimental plot before them was treated and reiterate the role of this plot in the objectives for the course. Students then turn to
their first task of making observations about the current abundance and distribution of plants in experimental plot.
Comments On the Activities in the Lab.
I have always told students to be prepared for all weather conditions. This must be covered during the week prior to the first laboratory of this
experiment and it should be part of the syllabus. Remind them to bring sturdy shoes, rain gear, pencils, water, and sun screen. Thunder and
lightning and/or a drenching rain will scuttle the field work for the day. If you are kept from working a particular day, look ahead to see if you
can have students organize themselves for the upcoming work. You might also rearrange some of the laboratory mini-lectures to fill in this
Have good instructions available with the equipment for the experiment. Students may want you to tell them what to do at every step. Turn
this around and tell them to follow the directions carefully so they can figure the equipment out for themselves. That said, know your equipment
well enough to know which equipment is too complex to use without instruction.
I borrow some of the laboratory equipment (e.g. graduated cylinders, mass scales) for this experiment. This has worked well at my institution,
but it may be an issue for some people. If you do borrow equipment on a weekly basis, give yourself time to gather materials before the
laboratory starts. If you will not be able to borrow equipment as needed you will need to budget for these items.
I have not taught any students with disabilities in this course yet. Always work closely with your “Office of Disability Services” to develop
appropriate accommodations for students with disabilities.
The text of this experiment has been written with a bias toward differences in plant abundance and distributions in space and not in time.
There is no reason why this experiment does not lend itself to hypotheses about time. Students would need some historical records about
the abundance and distribution of plants in the experimental plot to support hypotheses about temporal changes. Even 1 or 2 years of data
beyond the current year’s data would provide interesting fuel for students’ hypotheses. I do not yet have these historical records (i.e. I have
not done this experiment multiple years).
When I first designed and organized this experiment, I thought it would be interesting to take a good set of hypotheses with their experimental
designs and apply these designs to the experimental plots for the class. As I implemented the experiment, I realized that laying an experimental
design over the experiment plot would greatly change the nature of this exercise. In terms of future classes, this would tend to constraint the
range of possible variables that students would consider. I do not want to limit the range of hypotheses that students might consider in the
future and therefore will not try to “implement” experiments on the experimental plot. The possibility of students implementing their designs is
outside the scope of this laboratory. I am comfortable with my focus on hypothesis generation, experimental design, and proposal writing
because these parts of the scientific process are not, generally, as well covered as other parts of the process. Students get ample opportunity
to learn technique, generate data in experiments, and draw conclusions from these data. They spend less time on the initial observations
and hypotheses. I have received several comments from my students to this effect. However, my institution, like most other undergraduate
colleges and universities, has an active undergraduate independent research program. The proposals written in this experiment would be
excellent starting points for potential research projects.
Comments On Questions for Further Thought:
Comments on Question 1: Discuss relationship between factorial designs and interactions…
I introduce the concept of variable interactions, both conceptually and graphically, in the lectures for this course. Students should describe
interactions and give examples of synergisms and antagonisms. The attached spreadsheet (interaction.xls, 26kb)
shows examples of graphs where there is a) no interaction, b) an antagonism, or c) a synergism. They should describe a simple factorial
experiment that provides information about, at least, two variables acting simultaneously. For example, a simple factorial experiment
might include soil moisture (watered to field capacity twice weekly and watered to field capacity once weekly) and herbivory (herbivores
excluded or herbivores not excluded from experimental units) as independent variables and number of seeds produced as dependent
variable. The experimental design assigns all the possible combinations of soil moistures and herbivory to experimental units
(2x2 = 4 possibilities). Given this background, students should discuss how this experiment is the method to measure potential
interactions among independent variables. Both antagonism and synergism are interactions. This 2x2 factorial experiment is the
simplest factorial combination possible. As seen in the graphs, no interaction means that when you add the effect of water (seed count
change between points A and B) and the effect of herbivory (seed count change between points A and C) this adds to the effect of both
variables together (seed count change between points A and D). This is the same as the effects of the two variables on seed count
being “additive.” When the effect of two variables together is less than the additive effect, it is an antagonist effect. When the effect of
two variables together is greater than the additive effect, it is a synergistic effect.
Comments on Question 2: Presence or absence of seeded and volunteer plants….
Seed addition experiments are used to distinguish between dispersal limitation and competition as processes determining the presence
or absence of species in a space. An experimental design that varies the density of seeds placed in plot can show whether or not the
amount of dispersing seeds limits the establishment of plant species. A design that varies the density of standing plants in experimental
plots can show whether or not density (i.e. competition) impacts the establishment of plants.
Comments on Question 3: Describe broad goals and specific hypotheses….
Students have had a difficult time distinguishing between and articulating the difference between the broad concepts and the specific
hypotheses addressed by their experimental programs. It is therefore useful to have the students think about the “big picture” versus the
“details” of their experiments early in this process. The goal of this question is to have students think about and clearly state the conceptual
problems covered by their experiments and the specific dependent and independent variables that are meant to measure these conceptual
Comments on Question 4: Pick your favorite abiotic dependent variable ….
This question asks students to apply their knowledge of factorial experiments and interactions. I will use the example of water level,
herbivory and carbon fixation. Water availability is an abiotic variable, herbivory is a biotic variable, and carbon fixation is a dependent
variable. A 2X2 factorial experiment would create treatments where each independent variable had 2 levels. So, this experiment would
create low water and high water availability treatments. The experiment would also include low and high level herbivory treatments. All
of the possible combinations of these variables are treat 1: low water and low herbivory, treat 2: high water and low herbivory, treat 3: low
water and high herbivory, treat 4: high water and high herbivory. The easiest way to approach this is to create a graph and describe the
outcome. A graph with no interaction between water level and herbivory will show 2 parallel lines. Let’s say the X-axis shows water
level and the Y-axis shows carbon fixation. The lower line on the graph would be for high herbivory and the upper line on the graph would
be for low herbivory. Each line has a positive slope because as you increase water availability to a plant carbon fixation will increase (i.e.
the plant is not water stressed). The line showing low herbivory is higher than the line showing high herbivory because herbivory removes
photosynthetic area. I think the most sensible description of an interaction between these variables is one where the low water and high
herbivory treatment decrease carbon fixation more than expected. Therefore, the mean difference between low water:low herbivory point
and the low water:high herbivory point is greater than the mean difference between the high water:low herbivory point and the high water
and high herbivory point.
Comments on Question 5: As a plant ecologist let’s say you are interested in conserving populations ….
This is an open ended question that could have practical and / or philosophical answers. One might discuss the importance of focus.
If we are interested in conserving a particular plant, then the research should focus on the ecology and population dynamics of that particular
plant and not a much broader set of plants. There could be population demographic reasons (e.g. demographic stochasticity) that have made
the plant endangered that have little to do with the surrounding plant community. That said, it is clear that an individual plant does not live
in isolation from the other plants in the community. It makes sense then that we need to know something about the endangered plant and
the other plants in the community that are interacting negatively and possibly positively with the endangered plant. Some students may
take the stance that if we have limited funds to conserve this plant our focus should be on the plant of interest and not a larger community
that might require more resources. If the initial research on the individual plant requires us to research the broader community, then do that
in the future. Some students may take the stance that it really is not worth our resources to conserve an individual plant just because it is
endangered. It is really habitats and environments that we should be conserving and therefore we must always investigate the characteristics
of whole communities.
Comments on Question 6: The hypotheses / questions you have proposed have probably dealt with the distribution and/or
abundance of plants in space….
Students in this class, to date, have focused exclusively on questions across space and not across time. This could be a result of my biases.
This question is designed to have students explore the ideas of their variables changing within a growing season or from year to year. I touch
on experimental designs that measure variables over time and introduce repeated measures designs and non-repeated measures designs like
split-plot designs. Students might describe using one of these designs or might discuss an experiment that must run across several years.
Comments On the Assessment of Student Learning Outcomes:
The Table describing "Inquiry Framework: Levels of Student Ownership"
makes explicit a range of objectives for inquiry-based teaching: teach
existing knowledge, teach the process of knowledge construction, or create new knowledge. My objective in this experiment is to teach
the process of knowledge construction. Therefore, my focus for assessment of student learning outcomes is how well students show they
have learned these processes and tools that scientists use daily such as literature searches, annotated bibliographies, critical analysis of papers,
and writing proposals. Because of this focus, my student assessments such as the proposal grading rubric
(see Week 13: Research Proposal Final Assessment Form)
looks more closely at how a student has constructed the proposal than at the concepts that the student has included in the proposal.
Comments On the Evaluation of the Lab Activity:
Evaluation is discussed above.
In addition, extensive notes on how to conduct
formative evaluation are in the Teaching Resources sector
of TIEE under the keyword "Formative Evaluation."
Comments On Translating the Activity to Other Institutional Scales:
The fact that I used a created experimental garden should not be an impediment to the translation of this activity to any
particular place. I believe almost any plot of similar size could be used to motivate the generation of hypotheses / questions
for an experimental proposal. In fact, over time it would be interesting to use different plots as each plot’s history and current
environment should create different potential questions.
I believe the general format of this exercise would lend itself to a long term project in a high school biology or environmental
science class. This process allows students to explore some of the details of observation and question formulation that precedes
experimental design and experimentation. From my experience, the average freshman undergraduate has had little experience
formulating clear and focused questions with measurable dependent and independent variables. Much more direction would be
required for data collection, data sharing, and data analysis. One difference between upper level undergraduates and high school
students is their level of exposure to ecological concepts. A preview of potentially important factors for the distribution and
abundance of plants would help fill some of this gap. It would also be appropriate to limit the potential ecological concepts that
students would consider for experiments. This would allow the instructor to preview few concepts in more detail before beginning
I have down played the potential for this format as a lower level laboratory experience because, in my experience, most instructors
would not want to relinquish this much laboratory time. At my institution, our freshman-level biology laboratory is still a content
oriented course with much potential for inquiry-based learning. It is currently constrained to follow along with the content schedule
of the lectures. Without these constraints, excerpts from this format could be used in lower-level biology laboratories. One example
was given in the short description of “Transferability.” Students might also be given several sets of hypotheses from which to choose.
After some background on experimental design, they could design appropriate experiments to test their chosen hypotheses. There is
a tradeoff though for using excerpts from this extended experiment: loss of ownership by the students. The more information given to
students and not generated by students means they are less invested in the project.
This experiment could be transferred to a quarter system schedule by moving some of the current activities out of class time and
combining 2 or 3 laboratories. In short, the schedule could easily be compressed. For example, week 9 on the schedule shows
that annotated bibliographies are due and I would give time for oral presentation preparations and questions. This preparation and
question time could be moved out of class time and the first oral presentation moved forward a week. Peer and supervisor reviews
could also be done outside of class time. The line transect method is currently taught outside of the context of this experiment. It
is covered the week prior to the introduction of this experiment. This transect methods instruction could be done at / on the plots for
the experiment and the initial plant abundance / distribution data could be collected during this instruction. The students get some
initial practice formulating hypotheses during this transect methods instruction lab, but I believe this practice could be lost with little