Your Name: 

Your Email:

Study of Protozoa

Exercise 1:  Investigating ciliated protozoa

Study of Stentor coeruleus

    Prepare a wet mount of living Stentor coeruleus as follows. Add one drop of Stentor from the bottom of your tube and one drop of methyl cellulose to your wet mount to slow the movements of these active, trumpet-shaped organisms.  You should be able to view the organisms using a low magnification.  Keep in mind that Stentor is not pigmented (it is transparent), so you are not looking for something very colorful to view.  When seen in the microscope, Stentor appears as gray or tan-colored organisms that move through the water in a spiraling manner. Find a Stentor that doesn't move much and observe this individual under high magnification as well.

1. Do the cilia beat simultaneously or sequentially?  (you can probably see the longer cilia near the oral groove best to answer this)   simultaneously    sequentially
2. Does the beating pattern suggest a synchronization of movement?  yes    no
3. Look for the oral groove, nucleus, and food vacuoles within each cell.  You may or may not see them all.  The food vacuoles are just large vesicles containing food that were taken in during endocytosis at the tip of the oral groove.  Which of these did you find?    oral groove    nucleus    food vacuoles  (check all that apply)
4. Can you see that there are cilia arranged in rows all over the outside of the cell?  It might be possible to see that the cell looks like it is lined, kind of like the potato chips that are advertised to "have ridges."  These ridges are lines of cilia.  Do you see all these ridges?  yes    no

Study of Amoeba proteus

    Make a wet mount of Amoeba. Using your lowest magnification setting, scan your slide for a grayish, irregular-shaped object.  Tilting your light around a bit might help you see this organism. If after a few minutes you have still not located an amoeba, rinse your slide and try another drop. Persistence is the key to finding these organisms!

    Note the irregular shape, the slow movement (streaming) of the cytoplasm, and the formation of pseudopodia.  You should get a sense that the pseudopodia are formed as the cytoplasm within the cell flows in a particular direction.

1. List 2 functions of pseudopodia:
2. Describe the appearance of the cytoplasm inside the cell.
   

Study of Volvox

    Volvox is a colonial organism composed of many individual cells bound together by a gelatinous secretion and is commonly found in freshwater. Each colony may consist of a few hundred cells to 50,000 cells. Each member of the colony contains all the same structures as Chlamydomonas (stigma, flagella etc.). Flagella are beat by members of the colony in a synchronous fashion, which allows the colony to move through the water in an orderly manner.

    Prepare a wet mount of Volvox and sketch all visible features. You do not need to use methyl cellulose to view make this wet mount.  Note the daughter (reproductive) colonies found within some of the colonies that you observe.  Daughter colonies may be produced either sexually or asexually.  Link from here to see a good website to view Volvox.

1. Describe the way that Volvox appears to move.
   
2. What color are the cells of Volvox? 

Study of Spirogyra

    Yet another common green algae is "pond scum" or Spirogyra. Spirogyra is bright green and occurs in multicellular thread-like strands called filaments. Each filament is composed of several to many cells linked end- to-end.

    Prepare a wet mount of Spirogyra and examine beneath the microscope. Note the characteristic spiral-shaped chloroplasts.

3. Note the filamentous shape of the algae. Are the filaments branched? yes    no
4. Can you see cell walls separating the individual cells of the filament? yes    no

    Look for a nucleus within each cell of the filament. The nucleus is suspended in strands of cytoplasm, much like a spider might be found sitting in the center of a web.  Sometimes it is easy to see, and other times it is just not visible.

Study of Ulva

    An abundant marine multicellular species of green algae is "sea lettuce" or Ulva. The body of Ulva consists of a tiny root-like holdfast that anchors the algae onto rocks or other substrate on which it is growing.  Ulva is only a few cell layers thick.  Ulva is a bright green, almost transparent seaweed.  Take a little piece of Ulva and make a wet mount of it.

5. How many different types of cells do you see in Ulva?  Explain.
   

Study of Diatoms

    Make a wet mount of diatomaceous earth.  You have received diatomaceous earth, which is basically dead, dried out diatoms.  All that is left of the diatoms is their cell wall.  If you had received live specimens, you wouldn't see much more than what you can see with the dead organisms because their cell walls are so thick.  To make a wet mount, really just put a drop of water on a teeny bit of diatomaceous earth dust (you do not need a lot-- if it looks like a big white splotch you have too much).

    Note the variety of shapes exhibited by these organisms, and their unicellularity.  You will see that some of diatoms stick to others and seem to make short filaments, but they don't stay together or make long filaments like you saw in Spirogyra.

1. How are the diatoms shaped?
   
2. Do the diatoms seem soft or hard?  (explain)
   

1. Note the filamentous shape of the algae. Are the filaments branched? yes    no
2. Do the cells look soft or hard?    soft    hard

3.  Do you think that kelp looks like a simple multicellular organism or like a complex one?  We both know it is classified as simple, but classifications change all the time.  So what do you think and why?

End of Lab Questions

1. Approximately 100,000 species of protists have been identified and classified. Most taxonomists, however, believe that this number is low and that many thousands more await discovery by humans. Explain why you think it is so hard to find new species of protists.

2. Why are algae not classified into the plant kingdom? List 2 reasons.
Reason 1: 
Reason 2: 

3. On your first day on the job as Naturalist at Cape Cod National Seashore, an angry visitor approaches you complaining about all the "good fer nuthin seaweed" littering the beach.  Explain to the visitor 5 ways humans benefit from algae.

4.  Identify an organism that you viewed that could be considered "phytoplankton."