Challenges to Anticipate and Solve:
This lab is designed to introduce students to ecological experimentation and enhance their understanding of the
scientific method. Most of the students have never conducted a field experiment and their only knowledge of the scientific
method is from textbooks. These exercises are designed for biology majors with little to no field experience. However,
these exercises could be modified for use in non-major undergraduate courses as well.
Questions addressed and ecological context:
This lab gives students a better understanding of the scientific method and how ecological studies are conducted in the field.
This exercise is designed for two, 2-hour laboratories. However, modification could be made to reduce the time requirements.
Challenges to anticipate:
1. Working in the field. Most students have little or no knowledge of what to anticipate in a field setting (i.e.,
rain, ticks, sun, mosquitoes, dehydration, and poison ivy). Students should be forewarned and encouraged to wear long pants
and closed-toe and heel shoes, as well as bring a bottle of water. The instructor or TA should bring insect repellent, suns
creen, a first-aid kit, and a large container of water with cups.
2. Hypothesis development. The Instructors or TA's should help the students formulate their own hypotheses. These
experiments were designed to allow the students to design their own experiments and develop a testable hypothesis. However,
it is the responsibility of the instructor or TA to decide if a hypothesis is testable before the experiment is conducted. The students are usually
very enthusiastic about this exercise, so much so that they may try to use too many treatments. Instructors and TA's need to encourage the
testing of a simple, one treatment, hypothesis. The hypothesis needs to address an ecological response to a treatment and not the
experimental treatment itself. For example, fertilizer is used as a test of the effect of soil nutrients on plant growth. Ecologists are rarely
interested in fertilizer itself.
3. Experimental design. The students need to be encouraged to think about ensuring adequate replication, controls, and to avoid
pseudoreplication (false replicates) in the design of their experiment. Most students do not understand the difference between a control
and a variable in an experiment. In addition, many students need instructional guidelines and descriptions before being able to design a
good controlled experiment.
1. Arrange for transportation to the study site.
2. Plant Brassica rapa seeds (dwarf and wild-type) 6 to 7 days prior to the laboratory meeting to get 4-day old seedlings
(follow growing recommendations provided by Carolina Biological Supply). It takes us about 10 hours to plant the seeds
(1680 plants for 280 students), and additional time is needed daily to water the seedlings.
3. Gather sampling equipment (i.e., wire flags, light meter, wind guards, insect netting, fertilizer, pins for pin
counts, insect vials, rulers, chi-square tables, alcohol, markers, forceps, meter tapes).
4. For large classes, equipment needs to be made ahead of time. A small class or more advanced class could make
their own materials with the supplies provided. We usually prepare some items ahead of time anticipating what we think the
students may need:
a. fertilizer - We use Miracle-Gro and make up four differing strengths. We also provide the students with empty squirt
bottles and water in case the students want to make up their own fertilizer strengths.
b. differing pH buffers - We usually start out with pH’s of 4, 7, and 10. At student request, other buffers
with other pH's can be made.
c. salt water in plastic dropping bottles - We use 5%, 10%, and 15% concentrations.
d. sugar water in plastic dropping bottles - We use 5%, 10%, and 15% concentrations.
e. gibberellic acid solution - We use 10 PPM in a spray bottle. The students can determine the amount of
application by the number of sprays and frequency of the sprays applied to their plants. Note: the students will see a
marked change if they apply the gibberellic acid to the dwarf variety of Brassica.
f. We provide additional empty squirt and spray bottles for the students' use.
g. wind guards/insect guards/mammal guards - We make wind guards out of flags and plastic soda bottles, insect
guards out of insect netting, and mammal guards out of chicken wire.
h. We allow the students to be creative and come up with their own ideas as well.
Comments On the Lab Description:
Introducing the Lab to Your Students.
Students are asked to list the steps of the scientific method, given a brief tour of the field site, and are provided with
maps outlining the treatment regiments (e.g., mowing, fertilizer, etc.). We also discuss the available plant material and
available equipment. This experiment was designed to be somewhat vague to foster inquiry in students. However, we require
each group to discuss their hypothesis with the instructor to make sure to many variables are not being tested.
Comments On the Activities in the Lab.
We provide students and instructors with separate handouts. These handouts can be obtained from the following URL’s:
Comments On Questions for Further Thought:
These are discussed after the oral, in-class presentations, if time permits.
Comment on the Question: What is the value and/or limitation of field experiments?
Field experiments help students and scientists understand natural phenomena in a hands-on way that is not possible through
reading or laboratory exercises. It also allows them to understand the work that ecologists do, by experiencing the science
first hand. Field experiments are more difficult to conduct than other kinds of experiments, because field conditions can be
unpredictable. Experimental plants may die suddenly (e.g., herbivores, unexpected bad weather, or students may forget to
water plants). The biggest problem can be that the experiment creates unanticipated conditions for the experimental plants.
For example, a cloth that is designed to shade a plant causes it to overhead instead. The results of the students’ treatments
may be very unanticipated.
Comment on the Question: How does scientific research help us understand better the natural world?
Scientific research helps students to develop the skills necessary to make and process observations about the natural world.
Comment on the Question: Why are native ecosystems useful for ecological research?
Native ecosystems are useful for ecological research since these are the systems that ecologists are attempting to understand.
Manipulated systems can also be useful if these help to isolate particular experimental or environmental factors in the experiment.
Comments On the Assessment of Student Learning Outcomes:
We chose this method because several TA’s grade the papers and this breakdown provided an objective template for grading.
Comments On the Evaluation of the Lab Activity:
Many undergraduate ecology courses are taught primarily through lecture with little to no hands-on experience.
This laboratory provides students with the opportunity to learn through inquiry.
In addition, students have a better understanding of the scientific method, hypothesis development, and real-world investigation.
Improvement in the evaluation scores demonstrate a higher understanding of succession and ecological processes,
which the students have learned via the inquiry learning method used in the laboratory. The before and after scores
in particular help the teacher evaluate the amount of improvement in student understanding before and after participation
in the laboratory. The before and after scores can be statistically analyzed and used to demonstrate to administrators
the efficacy of this and other teaching techniques.
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:
Assign students to groups the week before the experiment is conducted. Provide the laboratory materials that week and have
the students meet outside of class to develop a testable hypothesis.
Have students choose from three testable hypotheses (provided by the instructor), make predictions, conduct the experiment,
and present how their results compared to their predictions.
If No Field Site Is Available:
Have students design an experiment and prepare the seedlings in the laboratory. The TA or instructor can place the plants
in appropriate conditions for the week. The seedlings can be brought back into the laboratory the following week for measurement.
Have each group of students’ design a unique experiment using rapid cycling Brassica rapa . They may also create their own
sampling equipment instead of having it provided to them. Data from different sections or years could be combined for more rigorous data analysis.
The students may go to the field site if terrain is suitable for wheelchair use. Most universities will provide handicap
transportation. If the terrain is unsuitable, have the student’s group set-up the experiment in the laboratory. The instructor
and/or students can transport the plants to the field site. The plants can be brought back to the laboratory the following week
for “after” data collection.