Biol 206 Foundations Ecology and Evolution Lab
Independent Plant Ecology Experiment
The plant system you learned to use for the Plant Interactions Experiment can be used to investigate many other
ecological and evolutionary research questions. Identify an interesting ecological or evolutionary research question, then
design an experiment to address this question using the plant system.
To come up with your research question, think of questions related to topics covered in lecture. The following questions
are very general, but might give you some ideas as you develop your own, more specific, question.
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Is a specialist species a stronger interspecific competitor than a generalist species?
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Which species in a group of species is the best intraspecific competitor?
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Which species in a group of species is the best interspecific competitor?
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Is the best intraspecific competitor also the best interspecific competitor?
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Does competitive exclusion occur between two species with similar ecological niches?
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Does the outcome of interspecific competition change in different environments, or is the best competitor
always the best competitor under all environmental conditions?
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Similar to the question above – Some pairs of species compete in favorable environments but facilitate
(support) each other’s growth in poor habitat. Do any of our plant species do this?
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Does the outcome of interspecific competition change depending on when the second species is introduced
to the habitat?
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Does the species richness of a community affect its invasibility? In other words, does the number of different
species found in a community influence the growth of an invader introduced to the community?
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Does the species richness of a community influence its stability during stressful environmental conditions?
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Does the level of disturbance influence the number of species that can coexist in a habitat? (Testing the
intermediate disturbance hypothesis)
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Does mild herbivory influence the growth rate of plants? (Herbivory can be simulated by periodically snipping
the plants a little.)
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Does herbivory influence the outcome of competition between two species?
We have various materials you can use to set up your experiment:
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Seeds – Wheat, Mung Bean, Pinto Bean, Lima Bean, Soybean, Pea, Corn, Barley
Soils – Propagation Mix, Pro Mix HP, Sandy Loam, Peat Moss
Fertilizers – Bone Meal, Osmocote 13-13-13, Osmocote 18-6-12, 5-10-5 Fertilizer, Super Phosphate 0-16-0, Lime
Water – Distilled, Tap
*Do not vary the amount of water you use in your experiment unless you are willing to come in every day to water
your own pots.
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Light – Florescent bulbs, Grow Lights
You are not necessarily limited to these materials. If you want to use something not in this list, let your lab instructor
know. We will see if we can get it for you.
All experimental treatments will be set up in 2” square pots. You will have 12 pots to work with. Think about how you will
divide these pots among experimental treatments and replicates. You want to have as large a sample size as possible,
so you should use all 12 of your pots.
In designing your experiment, consider the statistical analysis you will do. You will probably have two groups of plants
which may or may not be different from one another at the end of the experiment. Depending on your experimental
treatments, the two groups of plants might have different biomasses or different heights. They may have a different
number of leaves or be a different shade of green. Think about the type of data you will collect – your dependent variable
– and how you will determine whether the two groups of plants truly differ in this trait. You can compare the means and
variation of the two groups with a t-test to determine whether the differences you see are simply the result of random
variation or whether these differences arose because of how you manipulated the independent variable.
Names: _________________________________________________________________________________________
BIOL 206 Foundations: Ecology and Evolution Lab
Experimental Design: Independent Experiment
As a group, develop an interesting research question that can be addressed with plant seeds germinated and grown in
small plastic pots under light banks. Design the experiment using this sheet to guide your thinking. If you have questions
as you work, ask your lab instructor. When you finish designing your experiment, give this sheet to your instructor. Your
instructor will check that your experiment is feasible and uses materials that we have. You will set up this experiment next
week.
*Be sure your answers have a lot of detail. Detailed thinking now will make setting up the experiment easier next week.
Research question – _______________________________________________________________________________
Null Hypothesis (H0) – ______________________________________________________________________________
Independent variable – ______________________________________________________________________________
Experimental treatments (conditions) – _________________________________________________________________
Control treatment – ________________________________________________________________________________
Dependent variable – _______________________________________________________________________________
Standard conditions – _______________________________________________________________________________
Number of replications – ________________ (You will have 12 2-inch square pots to work with.)
Materials Needed for this Experiment (be specific – write exactly what you need and how much of each item):
_________________________________________________________________________________________
_________________________________________________________________________________________
_________________________________________________________________________________________
What is your Alternative Hypothesis (H1) for this experiment? ______________________________________________
____________________________________________________________
What is your prediction for this experiment? _____________________________________________________________
_____________________________________________________________
How will you analyze the data you collect?
____________________________________________________________
_____________________________________________________________
Additional Notes:
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