Teaching Session: My Favorite Ecology Laboratory Exercise
Presiding: R Fuller, Colgate University; M McTammany, Bucknell University
NB33U-01 INVITED 13:30h
Web Resources For Teaching Ecology/Field Courses
Developing ecology/field courses can be challenging, if not overwhelming. Factors like weather, travel time, necessary equipment, and simple logistics all may compromise our ability to provide a spectrum of exercises and lab experiences that are both meaningful and engaging. If one also considers the simple everyday demands on our time, such a task becomes daunting indeed. The good news is that there is help out there. A plethora of instructional resources are available right at your fingertips on the web. We will present an array of different web resources for teaching ecology/field courses that will include everything from specific exercises to extensive, searchable databases of instructional resources. Web based teaching resources provide instructors with means to share, expand, and enhance their courses and course materials.
NB33U-02 INVITED 13:45h
Twenty-eight Days to a Climax community: A Succession Laboratory Using Periphyton
Succession in benthic algal communities (periphyton) occurs in a relatively short time scale because of the rapid reproductive rates of algae. To examine primary succession of periphyton in a lake and stream, unglazed tiles are placed in the respective habitats and sampled on days 4, 8, 16 and 28. Students count the preserved samples at 400X and identify taxa to genera based on customized picture keys (does not require a high degree of instructor expertise). Genera also are categorized according to algal growth forms, based on the size, shape, motility and attachment mechanism. After pooling the class data, students present the change in community structure, contrast succession between the lake and stream, and hypothesize which mechanisms may apply (facilitation, inhibition, tolerance). Successional sequences also are examined to see whether they agree with published growth form models for periphyton succession in lotic and lentic habitats. The laboratory uses the more intuitive method of repeated measures to study succession as an alternative to the often infeasible chronosequence method traditionally done for terrestrial communities. Additional outcomes include, reinforcement of the concept of species guilds (growth forms), an introduction into the use of empirical models, and an increased awareness of microorganism communities.
NB33U-03 INVITED 14:00h
How Ecosystems Breathe: Measuring Respiration of Soil
Curriculum for general ecology labs often uses in-lab exercises and computer simulations to demonstrate ecological principles rather than experimental field projects. In addition, ecosystem processes can be difficult to incorporate into general ecology labs because the techniques require sophisticated equipment or complex field designs. As an alternative to in-lab projects, I have integrated field measurement of soil respiration into my general ecology lab to teach students aspects of experimental design (sampling, replication, error, etc.) and to demonstrate how organism-level processes operate beyond single organisms in nature and are influenced by environmental conditions. In a program laden with biomedical interests, analogies between organisms and ecosystems are quite appealing to students. Students in my general ecology course complete a 2-week field project in which they measure soil respiration inside a dark microcosm chamber. We use 10% KOH to trap evolved CO2 and titrate unreacted KOH in lab using 1N HCl. The protocol is simple, only requires some chemicals, and can be used in many different habitats (including flower beds on campus) quite easily. Potential experiments could involve varying environmental conditions, such as soil moisture, nutrient availability, gaseous environment, carbon supply, or temperature, to affect soil respiration rate.
NB33U-04 INVITED 14:15h
Skeletons in the Stream: A Temporal Study of In-Stream Leaf Decomposition
Allochthonous leaf litter plays a pivotal role in streams. Laboratory exercises highlighting its ecological role can examine several components simultaneously. The rate of leaf decomposition is an ecosystem-level process that represents the composite effects of microbial, invertebrate, and physical activity. Leaves that fall into streams often cluster together in "packs" behind rocks and woody debris. In this exercise, students construct leaf packs by collecting leaves from surrounding vegetation or the ground. The leaves are placed into plastic mesh bags and secured in the stream. Subsets of the packs are collected at weekly intervals, colonizing invertebrates are removed and identified, and the remaining leaf material is dried and weighed. Students design and carry out their own experiments, the broad areas of which can include; (1) decomposition rates among streams or leaf type, (2) upstream-downstream effects, (3) distribution of shredding invertebrates, and (4) land-use correlations. We will present examples of results from both high school and college level experiments along with recommendations for successful implementation.
NB33U-05 INVITED 14:30h
Fish Population Estimates: A Comparison of Methods
This exercise is designed to demonstrate two methods for determining the density of mobile animals. By sequentially sampling fish in a pool we estimate fish population size using the Removal-Summation Method (RS), and then we mark and release the fish. The next day a second lab section returns and repeats the sequential sampling and also records the total number of fish marked and unmarked so we can use the Capture-Mark-Recapture Method (CMR) as a second estimate of fish population density. I often use this as the first exercise in my ecology class to make students aware of the importance of measuring variability in data sets and to make them think about the assumptions that are made when using each of these methods. The difference in the estimated population size between days for the RS method is usually striking and they often get very different population estimates when comparing the RS and CMR methods for the samples taken on the second day. They must then consider which assumptions for each method might have been violated and explain how each might affect their estimates. Because we can obtain variability estimates for each method, they also can see just how much variability is associated with each of their population estimates.