To the List:
As always, many thanks for your ideas and suggestions. This list is a great resource for our community. I know that there is an abundance of ideas out there for this type of endeavor, i.e. for population biology in the college classroom, however I believe that real experience is very important. Reading about these exercises is often not sufficient to implement them. And our members have a wealth of information beyond what is publicly available. That said, please find attached a brief compendium of responses to my query. I tried to summarize and combine responses, so that the most informative information was included but redundancies were omitted. If you would like to connect with any contributors to this resource or would like copies of the resources, we can figure that out. Just let me know. And thanks again to everyone who responded, whether it was with a vote or hint or a chunk of their thesis. Todd Levine <http://tiee.ecoed.net/index.html> http://tiee.ecoed.net/index.html Provides an interesting set of experimental active learning methods with real hands on experiments and includes the full study plan..... TEACHING ISSUES AND EXPERIMENTS IN ECOLOGY ——a peer reviewed publication of ecological educational materials by the Ecological Society of America *************************************************************************** Each of my 12 student groups (two per group) designed and executed a semester-long experiment with various invertebrates. The most successful projects were the ones that used Daphnia or flatworms. Since I work on life-history evolution and phenotypic plasticity in birds, I inadvertently pushed the students to ask questions related to growth and allocation of resources in these organisms. Flatworms were cheap and the easiest to raise and keep. Daphnia eggs (even cheaper to purchase) actually took a bit of work to get them to hatch, since one need proper aeration, temp, etc. Brine shrimp were also very easy. Some of the projects: Flatworms: - Resource allocation in patchy environments, or something like that. Grotesquely, the students tested which was most important (cut half the tail off) to see if initial experience with patchy food resources would induce more allocation of nutrients to tails. I forgot the way they designed it. But there's a huge suite of stuff you can do with this. Daphnia - Of course, there's inducible defenses. All sorts of things the students would be interested in. - Growth rates in different levels of turbulence under different food treatments. Brine shrimp - One group examined density-dependent, nutrient-dependent, and pH-dependentgrowth rates over time (by subsampling populations). As I recall, the brine shrimp showed really cool differences in body morphology between the various treatments. There was also a group that examined body size and fighting in crickets. *************************************************************************** Wild Caught Daphnia Daphnia, daphnia, daphnia. Feed them well and they reproduce faster than you can feed them. You can collect them from the lake – if they are there. A zooplankton net will do to collect them. Or you can order them. You can very easily culture them in lab in flasks with bubblers or stirrers. You just have to prep algae or yeast to feed them. Here is a semi-cheesy website with some info: http://www.caudata.org/daphnia/ Do some searching and you should be able to find a ton of info. *************************************************************************** Our lab instructor has been using Fast Plants (http://www.fastplants.org/), which are a Brassica. Other plants in the Brassicaceae would also grow quickly (like Shepard's purse, etc.). If you wanted to look at demography of trees, you could use the point-center quarter method (see attached)--comparing density of trees of different size classes. ************************************************************************** Nematodes! They're the most abundant metazoan on the planet (about 8/10 of us are nematodes), and occur in nearly all microhabitats of all biomes, aquatic and terrestrial. Generally about 10-100 individuals per gram of soil or litter in forests, and they span several trophic groups: herbivores, fungivores, bacterivores, predators, and several omnivores. They also don't take up much space (usually around 0.5 to 1 mm long, sometimes up to 5 mm) Many species are culturable, and most culturable species are from the family Rhabditidae (also the family of C. elegans, which was the first, and probably best characterized to date, genome sequence of all metazoans). Many species can be extracted from the soil with pretty cheap, low-tech methods (like a napkin laid on a kitchen strainer) that have been worked out for soil ecology labs. One of the easiest ways to culture Rhabditidae is to seed an agar plate with a lawn of bacteria in the middle (like E.coli OP50, but several bacteria could be used), put 2-5 g soil around the outside, and just wait a couple days and see who comes out, and pick them onto new 'fresh' plates. Lifespan ranges from about a week to about a month, depending on the species (up to a year in some, but these generally are not very culturable). Generation time (egg to median egg) is usually about half that, so a pretty complete life-table analysis can be done within a month. Reproductive output ranges from a couple dozen to several hundred. Optimal growth temperature is usually around 20-25, but varies by species, so population growth assays can be done to test different species, or different temperatures, or different bacterial prey, or some combination of these and others. With a bit of work, experiments done on the lab petri dishes could also be scaled up to a pot or mesoculture setup. The small size makes them somewhat difficult to work with for the inexperienced, but a advantage is the very face growth rates that allow for relatively little 'down-time' between experiments. Let me know if this sounds of interest to you, and I'd be happy to send any directions, recipes for media, etc... I can. Identification of field-collected nematodes is tough, but I'd be happy to help (or provide 18S SSU primers for molecular ID, which is currently state-of-the-art for Rhabditidae, but not necessarily other families). Attached is a sort of pictoral key to some broad functional guilds that I used for an undergrad soil ecology lab. ******************************************************************* Aphids would work well: Generation time would depend on how warm it is where you're growing them, but when I grew cabbage aphid colonies for a research project, I "seeded" host plants with three "mama" aphids and within a week had nice little colonies started up on all but one host plant. To keep the parasitism under control--that is so that you keep your colonies separate--you might like to use paint-straining bags to keep each colony contained. I'm attaching a photo of when I used paint straining bags (kept tight with a bobby pin at the base because the elastic of the bag lost elasticity quickly in a sunny greenhouse) and thin solid pvc tubes (every ecological experiment requires at least one form of pvc, I think) to hold the bags up off the plants, though a tomato cage would work very well too, if you had some on hand. I did this to keep some moth larvae from being parasitized in the greenhouse since I was interested in field exposure parasitism. For my research, I needed "clean" aphid colonies, which was pretty challenging to create since I started up from locally "caught" aphids. To do that, I started out little aphid worlds from the caught aphids, about 13 of them, using only little aphid colonies that didn't have any mummies. Photo of that attached as well. I kept tabs on them for a few days, discarding any that had a parasitic wasp flying around inside. Within a week, I knew which 6 or so were actually "clean" and used these to start up my experimental colonies. If you aren't concerned with keeping an aphid colony free from parasitoids, it's very much more relaxing growing them! ***************************************************************************** I've used crayfish collected from a nearby stream and I've also ordered them from the Louisiana Crawfish Company (which is much cheaper than ordering from Carolina Biological). Not sure about generation times. I’ve mainly used them for mark and recapture experiments to determine population size and in behavioral assays (e.g., aggression, feeding preferences for aquatic macrophytes). Unless they eat each other, they’re pretty hardy and be kept in the lab for quite some time. ******************************************************************************* Nothing surprises my students more than realizing that there are tiny animals that live in flowers. One of the most interesting labs (from the students comments) that I give is on estimating population densities using two species of flowers. Here, we have mainly one collembolan that inhabits those two angiosperm species (both composites). The other main group are thrips, but those are far fewer. The basic design is simple. They cut a couple of flowers invidually into Petri dishes and put some drops of ethanol on them to kill the bugs. Then they can count flowers per area using quadrats, and calculate density per area. They can do this over time, at different scales, comparing patches, or for any possibility that is of your interest. I use this exercise to teach my students about estimating population densities and organism distributions first, and then have them sample the to flower species in the day and at night to teach them about using 2-way ANOVA. You can adapt this to any flower species that is in good numbers around the place, and that the students can recognize easily. Of course, getting a good preliminary sample to findout who lives in the flower never hurts. Hope this helps some. ********************************************************************** Mealworms work very well, I have used these for various kinds of lab experiments with students in class, especially used them to demonstrate nutrition, temperature effects on growth, etc.. Daphnia and brine shrimp are an easy aquatic invert to use. Planaria can be used to model foraging theory and to demonstrate negative phototaxis. Betta splendins works well for behavioral aggression. killifish (eggs available on ebay) can be adapted for various things too. It really depends a lot on what you are doing. ************************************************************************** My research uses the seed beetle *Callosobruchus maculatus*. A booklet available online is attached. There has also been a push specifically to use these guys for undergrad work (also attached). The beetles have a number of good lab model properties: 3 week generation times at 85 F Capital breeding (no food as adults) Low space requirements (tupperware/petri dishes) Sexual dimorphism Wing dimorphism Sexually selected traits (male size, male intromittent organ) Multiple host bean use Variation in host use and preference Rapid response to a number of selection pressures Maternal effects for many ecological traits. I love em! I have several populations if you need stocks. We have used them in our university's ecology course as well. Other researchers using them are Charles Fox and Frank Messina. Hope that helps- *********************************************************** I TA's in a course that used a duckweed (Lemna minor?). They reproduced asexually and quickly. Culture was simple, still water containers with a light source. You could design simple density dependent experiments. They tended to be infested by some herbivore flying insect that could lead to other questions. They are easy to find in the wild. Good luck. ********************************************************** I am the North American coordinator for a project called the "Global Garlic Mustard Field Survey", which you may be interested in. We have a number of academic partners who use the survey as a teaching tool that allows students to participate in a 'real' scientific project and compare their results to the global data set. There is more information on our website ( www.GarlicMustard.org <http://www.garlicmustard.org/>), or feel free to email me if you would like more details. *********************************************************** A vote for planarians! *********************************************************** Finally, a word of warning!!! I spend all my time working on invasive plants issues in Alaska. Most recently we found big infestation of an aquatic plant that is sold by Carolina Biological Supply (and other supply houses) for classroom use. Based on where this infestation began, it is very likely that it resulted from someone dumping an aquarium. Also, an interesting article I just read found that the distribution of non-native crayfish in Oregon is related to the locations of elementary and middle schools. That is, teachers are ordering them for science classes, then either the teachers or students are dumping them out at the end of the year. Please consider this situation if you buy organisms and please discuss with your students. Thanks! -- Todd D. Levine Post-doctoral Research Associate Hancock Biological Station Murray State University 561 Emma Dr. Murray, KY 42071 270-474-2272
