SUBJECT: Using protists for quantitative labs

DATE: 2/97

 

 

Hi Y'all!

 

Do any of you use protists in the lab? I am trying to develop some

labs that involve students in quantitative investigations of protistan

adaptations. An example would be to design a procedure whereby students

verify the osmoregulatory function of contractile vacuoles. I understand

that this is not a terribly original example. I am really looking for

quantitative exercises at this time. Anyone?

 

Yours,

Michael Dini

Texas Tech Univ.

y3mld@ttu.edu

 

 

The osmoregulatory function of the contractile vacuole is a VERY GOOD

example of an exercise that students can do quantitatively. Simply have

them investigate the frequency of contraction of the vacuole and the

rate of its growth under various osmotic pressures.

 

Another one that can be done is an investigation of cell feeding rate

with two strains of Paremicum caudatum feeding on yeast. Or offer one

strain two different foods - a bacterium and yeast.

 

Have fun,

 

Dave McNeely, Biology, University of Texas at Brownsville, 80 Fort

Brown, Brownsville, TX 78520; mcneely@utb1.utb.edu

 

 

There is the experiment based on the Competitive Exclusion principle

proposed by Gause (1934?) in which to species of paramecium (P. aurelia and

P. caudatum) are combined. The species most efficient at utilizing the

envirnoments resources should outcompete and eliminate the other. More

information can be supplied if you need it.

 

Michael Weber

Department of Biology

Carleton University

Ottawa, Ontario

Canada

K1S 5B6

mweber@ccs.carleton.ca

613-520-2600 (4493)

 

 

Hi Michael,

I've written a set of ecology labs that use protists to study population

and community-level phenomena. I'm packing up some sets of the protocols

to send out to people who have requested them (yes, I promise they are

almost ready to ship out ;)). I'd be glad to send you a set if you're

interested. We do quite a bit more analysis than the usual freshman level

competition labs. For instance, we have them calculate r, K, competition

coefficients, predator consumption rates, etc., but you could adapt them to

whatever level you need. I also include a mututalism cost-benefit exercise

although getting the cultures set up for this one has been a bear, and

still isn't working 100%.

 

Regards,

 

Liane Cochran-Stafira

Dept. of Ecology and Evolution

The University of Chicago

1101 East 57th Street

Chicago, Illinois 60637-5415

phone: 773-702-1930

fax: 773-702-9740

e-mail: lcochran@midway.uchicago.edu

 

 

>An example would be to design a procedure whereby students

>verify the osmoregulatory function of contractile vacuoles.

 

I like this question. I tried to get some multiple lab sections of first

year students to follow the contractile vacuole phenomenon using

Paramecia. The students as a whole did not have the patience to watch

the little critters long enough to find out. They just want to cook book

it and get out of the room. I was really disappointed in them. "Will

this get me into medical school syndrome" has really taken hold lately on

my campus.

 

Comments out there.

 

Blystone in Texas

 

--------------------------------

Robert V. Blystone, Ph.D.

rblyston@trinity.edu

 

Department of Biology

Trinity University

715 Stadium Drive

San Antonio, Texas 78212

210.736-7243 FAX 210/736-7229

 

 

Hi Michael, I think you are right, that protist projects can bring up

quantitative work very readily. Making solutions and dilutions, for

example. Or counting under the microscope. I would love to hear a report

from you that you've done this and it went swimmingly well (a bad joke

related to watching Paramecium).

 

I think protistan projects ought to be do-able even in freshman and/or

non-majors labs. However, I tried a few years ago and have since backed

off because it did not go very well in my labs. We did some organized

activities such as counting how many times a Paramecium changes directions

in a fixed time, and counting how many food vacuoles are filled in a fixed

time, as well as the timing of color change for the Congo-red stained

yeast we provided as food. Then we did student designed projects (groups

of 4-5 students) for which Paramecium might be chosen.

 

We had several projects actually done on Paramecium, including assessment

of contractile vacuole function. Those couple were OK. But the vast

majority of students rejected the whole thing -- they did poorly on the

organized stuff and had no interest in further projects in this area.

These were science, including biology, majors, by the way, about 700 of

them in labs of 20, taught by graduate students. Because of the disquiet

that arose around the initial quantitative microscopy activities, I

dropped those in future semesters. I did keep Paramecium as a possible

project area, but very soon there were no takers for this at all, and I no

longer even bring up the possibility with my lab instructors.

 

What's going on here? Has anyone got quantitative microscopy working well

in large enrollment freshman courses? My own imprssion is that there was

just too much - the quantitative techniques themselves challenged the

students, as did the microscopy, and the experimental design ideas that

went with doing projects (not even mentioning the writing!)- and the

students bailed out mentally. What I did was to simplify things and go

with macro stuff such as Brassica while trying to get "investigative labs"

to work. Still, I'd love to go back to Paramecium someday - the potential

is great! So go to it, Michael, and good luck! I'll be delighted to come

down to Texas to learn from you!

 

Robert B. Ketcham Biology (302) 831-2377

Laboratory Coordinator Univ of Delaware rketcham@Udel.Edu

Newark, DE 19716-2590

 

 

Biolabbers!

We piloted several exercises involving protists last week in lab. (I ought

to say that "lab" means 17 sections of majors' general biology laboratory.)

Our labs often begin with students performing exercises that will give

them skills necessary to observe and/or measure phenomena around which they

later formulate their own research questions and hypotheses and design

approriate tests. I wish that we had followed the same scenario for our

protist lab.

 

As Bob Ketcham noted among his students at U. Delaware, our students had a

hard time manipulating the microscopes to study moving organisms.

Certainly, they have used microscopes in our labs before, but practice

makes perfect, and nowhere is this more true than in microscopic studies of

protists. The pilot lab started them off immediately with making

measurements of various processes in paramecia: rate of contractile vacuole

contraction and timing of ingestion/digestion of yeast. Bad idea.

Students would have benefitted from a preliminary exercise wherein they had

an opportunity to develop skill in following swimming protists, get a feel

for the effectiveness of various techniques (found in the lab exercise's

appendix) to slow swimming protists and have time to just observe these

fascinating organisms. I will revise the protist lab so that it begins

with this opportunity. I will also make sure that students are provided

with RICH cultures of the protists; few things discourage students faster

than having to make and re-make wet mounts simply because the culture was

depauperate.

 

If (and this is a BIG if) students can successfully slow paramecium, then

they should not have to exercise too much patience to follow the activities

of particular food or contractile vacuoles.

 

Students also did a spin-off activity based on their photosynthesis lab

where they extracted spinach pigments and constructed absorption spectra of

the various pigments found therein. In this activity, they used the Spec

20 to provide indirect measures of Euglena density. Students filled

cuvettes with a rich Euglena culture, placed variously colored (red, green

and blue) cellophane filters around the cuvettes at the same level at which

the Spec 20's light beam passes through, covered the rest of the cuvette

with black construction paper and then illuminated the cuvettes from the

side with both fluorescent and incandescent lights for about an hour. The

idea was that the euglenids would become more concentrated in areas exposed

to wavelengths that were more efficiently used by their photosynthetic

apparatus. I haven't received reports from all of the TAs on results, but

students did get the idea and did come up with some pretty clever designs.

 

One of my students related a story from his high school biology course

where clear plastic tubing was used as the "reaction vessel." The tubing

was filled with a rich culture of Euglena and stoppered at both ends.

Variously colored cellophane filters were placed over stretches of the

tubing which was then illuminated. Following a suitable time period, the

filters were removed and students were to observe where Euglena had

congregated (detectable because that part of the tube would be greener than

parts where there were fewer euglenids). This is a qualitative

observation, but it seems to me that it could be made quantitative by

extracting samples from various parts of the tube (using syringes?) and

then having students microscopically census given volumes to determine

Euglena densities.

 

Again, I thank all who responded to my e-mail message last week about protists.

 

Yours,

Michael Dini

Texas Tech U.

y3mld@ttu.edu

 

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