Biology labs - aaarggghhh!!!

[BakersDozen]

We're just a few weeks into our Biology class and have had dismal failure when it comes to the labs. This week we were supposed to do skin cells and blood yet neither process for preparing the slides worked! Today we couldn't get the protist culture to show anything. I am so frustrated and angry! How hard can this be, really?? I have an excellent microscope and good instructions yet none of us can figure this out! If this was 2nd grade science I wouldn't be as frustrated/concerned yet given that this is with my 10th graders, I feel our time is being wasted.

 

Any thoughts/suggestions? Next week we dissect things like clams and starfish; hopefully we don't have as bad an experience as we've had with the slides! :glare:

[Julie in MN]

First, have you been able to view a slide of any sort with your microscope? I like to do a basic microscope lesson first, getting used to the different lenses and things. Typically you view the letter "a" cut out from a newspaper or something simple like that.

 

If you've used your microscope successfully to view something in the past, then I'm wondering what you mean about preparing the slide not working? Was anything at all visible? Do you have a light source, and have you tried adjusting the diaphragm to allow more or less light (typically all the way open at low magnification, and almost closed at high magnification)?

 

I think Biology labs are hard because it's not always easy to know just what you're looking at. But you should always see *something* that you can observe and practice recording in detail.

 

Julie

[BakersDozen]

Yes, we have seen slides before and familiarized ourselve with using the microscope. The first problem was with the skin cell lab where we were supposed to scrape inside someone's cheek and do a dry load. Nothing was there...absolutely nothing! Then we tried the blood lab and the stain just destroyed the slide specimen completely (since no one was anxious to volunteer the first time for a blood sample you can imagine their reaction when I asked for a second sample! That lab ended rapidly.) Then today's lab with the protists was a huge disappointment as we didn't see a single protozoa even after trying 8 times to prepare a slide! At that point I just got angry.

 

The only good thing was that my dc discovered a dead spider in a bowl of water so they spent time looking at that.

[Jean in Newcastle]

Human cheek cells

 

 

 

Not the same as doing your own but still worth seeing.

[StillStanding]

Experiments that worked for us

 

http://camillasenior1.homestead.com/cells.html

http://mail.ab.mec.edu/~fhohn/HBioLabs

http://www.lessonplansinc.com/science.php/biology/types/Experiment/

 

Online "slides"

http://www.kumc.edu/instruction/medicine/anatomy/histoweb/index.htm

http://www.mhhe.com/biosci/pae/botany/histology/html/ptmodov.htm

 

Google images of Protists

Information on Protists and good images

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookDiversity_3.html

[persinem]

I'm not sure what the problem is with preparing the slides. Maybe you should start with onion cells which are big and easier to prepare. If you google "onion cell lab" you'll find a lot of labs to choose from.

 

Also it could be your protist culture is still too new for you to be picking up organisms in a drop of water, or you could be taking the sample from a place where the protists are not hanging out. We bought a culture of amoeba that took several days before we could actually find the amoeba. There are ways to get protists to concentrate in a certain area of your culture, depending on what kind you have. Euglena will move toward light so covering the culture except for a thin band on one side of your culture will give you results. Paramecia congregate around a food source, such as a wheat seed (they are eating the bacteria that are attracted to the wheat seed, actually) so taking a sample near some cloudy stuff (the bacteria) growing on the seed or in the culture will usually get you paramecia.

[tex-mex]

We invested in this kit (prepared slides) and it was very much worth the $$ to be able to see under a microscope:

 

http://www.hometrainingtools.com/biology-microscope-slide-set/p/MS-SETBIO/

 

We did not have a state of the art (new) microscope -- but a 50+ year old student microscope that uses the sunlight or room light to illuminate the slide. It worked great!

[Julie in MN]

I'm not sure what the problem is with preparing the slides. Maybe you should start with onion cells which are big and easier to prepare. If you google "onion cell lab" you'll find a lot of labs to choose from.

 

Also it could be your protist culture is still too new for you to be picking up organisms in a drop of water,

 

:iagree:

 

That's about the only thing I can think of. But really, with the cheek and the paramecium, there should be some sort of... something on the slide? Even bits of the swab or... dust or something? That's why I suspected that the use of the microscope might need practice. I'd try the lowest magnification and the most light at first -- even a magnifying glass and flashlight if need be, to start with at least some sort of something to examine.

 

And when the stain is too strong, did you try pulling some off with a paper towel just barely touching the opposite edge? It might be harder with a liquid like blood. Next time, I'd try to spread the drop of blood onto at least 2-3 slides so you can try different things.

 

I'm no expert at "what" I'm looking at, but we should be able to see "something."

Julie

[LexiR]

I'm working with biology this year, and feel your pain. For the protist culture stuff, if possible, play around first with just drops of water (without slide covers). It's so much easier to see what is alive that way. Also, play around with a "clean" drop of water on the microscope first. I was amazed at what some of my "organisms" really were. For example, I now know what paper tail debris looks like magnified considerably.

 

Once you see alive protists literally swimming across your view, it will be easier to identify them flattened into place. You won't be able to use the finest tuning on the microscope this way, but you can still see a lot with the first two settings. The protist lab we did started with leaf debris, grass cuttings and water. We had alive stuff in just a few days when the water came from a well. I think it took a week with tap water. Again, looking at untreated water helped rule out things that weren't alive. Once we did have live stuff, it was undeniably alive, as it was swimming all over the place.

 

I'm having the same problems as you though, and working with unmotivated students (not my own, LOL!) I actually work in a small school, but am new to biology and learning this stuff with them. My supplies are also extremely limited, and I haven't been happy overall with our lab work. I did have an exciting few weeks myself though when I took the microscope and the protist lab home, ;) .

[TheHomeScientist]

The protist lab we did started with leaf debris, grass cuttings and water. We had alive stuff in just a few days when the water came from a well. I think it took a week with tap water. Again, looking at untreated water helped rule out things that weren't alive. Once we did have live stuff, it was undeniably alive, as it was swimming all over the place.

 

I'll second that. You don't need to buy protist cultures unless you really need examples of specific, known species.

 

You can get a huge variety of protists just by collecting some water, vegetation, and sediment from a pond or the edge of a stream. Also try to collect some pond scum (spirogyra). Put a layer of sediment on the bottom of a glass or plastic jar, fill it most of the way with pond water, and seal it. Allow the microcosm to incubate for a few days at room temperature, exposed to daylight (or a plant-grow light) but not direct sunlight, and you'll have all the protists you could want.

 

If that's not convenient, you can get a smaller variety just by making an infusion of grass or hay clippings in spring water or boiled tap water. (Chlorinated tap water kills off or greatly reduces populations of most protists.)

 

You can observe live protists just by putting a drop of the water from the microcosm or infusion on a slide. No cover slip is necessary. Some of the protists are fast movers. You can slow them down by adding a drop of methycellulose. If you don't have that, you can add a drop of glycerol (glycerin), which is available at most drugstores.

 

If you want fixed specimens, do a smear mount of water than has a high population of protists by spreading a drop on a slide, heat-fixing it with a flame source, and then staining it with methylene blue. If you also have eosin Y, you can counterstain with it to show additional features.

[TheHomeScientist]

Incidentally, different protist species have different preferences among the micro-environments in the microcosm. Some are found near the surface of the water, others free-swimming in the middle depths, others near or in the sediment at the bottom, and still others attached to or near the vegetation. When you're making wet mounts or smears, try using specimens from different parts of the microcosm.

[LexiR]

Thanks Robert! Lots of helpful stuff there. I'm pretty new to biology myself. The protist lab I did came straight from a textbook, and it suggested letting tap water sit for 48 hours to vent off gases. That will work too, though boiling water will certainly get you there faster. Thanks for the tip to try different levels.

 

Oh, if you do the dried leaves/grass cuttings, you don't need many leaves at all. At the school, we put a hefty amount in, and that "recipe" really started to stink after a few days. I repeated it at home with far less leaves, and it never got to the "hold your breath" stage.

[HoneyFernDotOrg]

Our best biology labs have been when we start with a structure and then allow ourselves to explore, going off the original lesson if necessary. Not only do we use the actual hands-on lab, but if we can't find or see whatever we are supposed to see, we supplement while doing th elab with online resources. Sometimes if we see online what we are supposed to see under the microscope then it is easier. Sometimes, too, we will run across something from an old lab and it will suddenly click.

 

Biology has been much more successful since we explored based on our questions, not just a curriculum, and we have "covered" everything a regular class would cover so far - maybe not in the exact same order, but with plenty of depth and all the vocabulary intact, and much more fun!!

[TheHomeScientist]

Thanks Robert! Lots of helpful stuff there. I'm pretty new to biology myself. The protist lab I did came straight from a textbook, and it suggested letting tap water sit for 48 hours to vent off gases. That will work too, though boiling water will certainly get you there faster. Thanks for the tip to try different levels.

 

Oh, if you do the dried leaves/grass cuttings, you don't need many leaves at all. At the school, we put a hefty amount in, and that "recipe" really started to stink after a few days. I repeated it at home with far less leaves, and it never got to the "hold your breath" stage.

 

One thing I forgot to mention that pertains to the original question. Like many microorganisms, many live protists are very difficult to see under a microscope because they're nearly transparent and have a refractive index close to that of the surrounding water. Using too much light may make them invisible, so it's worthwhile playing around with the dimmer switch and diaphragm.

 

Also, there are biostains called "vital stains", which means they can be used with live organisms without killing them. One of the most common and best vital stains is methylene blue. Adding a drop of it to the culture often makes any live protists present much more visible.

[persinem]

:iagree:

And when the stain is too strong, did you try pulling some off with a paper towel just barely touching the opposite edge? It might be harder with a liquid like blood. Next time, I'd try to spread the drop of blood onto at least 2-3 slides so you can try different things.

I'm no expert at "what" I'm looking at, but we should be able to see "something."

Julie

 

I found we didn't need to stain red blood cells--they have enough color to see them. But as Robert Bruce Thompson said above, if you have too much light coming in then you won't see anything, either. We have everything turned down all the way most of the time.

 

When we started out it helped that we were getting a lot of air bubbles under the cover slip--we could focus on those first and know we were at least in the ballpark!

 

Another thing we've done with protists is to use depression slides. You have a better chance of finding interesting things in your sample, it seems, and the protists don't die while you're observing them (under the cover slip they seem to dry out quite quickly), so they act more naturally. It gives us time to observe things like mitosis in paramecia, or amoebae movement/feeding in detail.

 

We're doing longitudinal studies--14 of them! where we observe cultures change like small ecosystems. Once you get the hang of finding them under the microscope protist studies are really a fine way to teach a lot of concepts.