LABORATORY EXERCISE #2

^{KINGDOMS MONERA AND PROTISTA}

Part I - Kingdom Monera

^Introduction

Kingdom Monera includes the most primitive organisms on earth, as well as those with the longest evolutionary history. The fossil remains of creatures such as these have been recovered from rocks formed as much as 3.8 billion years ago. The chief distinguishing characteristics of the monerans are derived from their prokaryotic form. Unlike all other organisms, the Monerans lack a true, membrane-bounded nucleus. The term “prokaryotic” comes from pro (before) and karyos (nucleus). The single cells making up these simple creatures, in fact, have no organelles at all! Although colonies of monerans are quite visible to the human eye, the individual cells are microscopic. The world’s smallest organisms belong to this kingdom. While there is evidence of sexual reproduction in some moneran taxa, most reproduce asexually by simply dividing. The monerans include:

^{A. The bacteria - These are the most well-known monerans for obvious reasons -- they are responsible for more human diseases than any other pathogen. Their importance does not stop there, however, for they function both for and against us in many less-spectacular ways. For example, they cause the decay of many substances, thus aiding in the recycling of needed materials throughout the ecosystem. They also convert the nitrogen in the atmosphere into a form which can be used by plants in the manufacture of protein. Without bacteria we would be deprived of such products as yogurt, sweet acidopholis milk, and cheeses like camembert and brie. Finally, the development of genetically-engineered bacteria is allowing the production of many useful items in quantities and at prices unheard of in the past.}

The three basic shapes of bacteria include the spherical bacteria or cocci, the rod-shaped bacilli and the spiraled bacteria or spirilli. These may form clumps, which are designated by the prefix "staph" (as in staphylococcus), or they may form chains of cells. These are called "strep" colonies, as in streptobacilli.

^{B. The cyanobacteria - Known previously as the bluegreen algae, these prokaryotic organisms are much like the bacteria, with one major exception -- they contain chlorophyll. This allows them to form their own food reserves through the process of photosynthesis. In all probability, these were the first autotrophic (self-feeding) organisms on earth.}

Though essentially unicellular, the cyanobacteria may form clump-like colonies or linear filaments. Color may vary from the typical bluegreen to a deep red, depending upon accessory pigments present. Habitats likewise are diverse, ranging from the surface of glaciers to the waters of hot springs and from rice paddies to desert rocks.

^{Like the bacteria, the cyanobacteria play the important role of nitrogen fixation. On the negative side, they are usually responsible for taste and odor problems in domestic water supplies.}

ACTIVITIES

^{a. Your instructor has set up three microscopes along the side counter. Briefly examine the slide on each and notice the general shape of the bacteria on each slide. Determine if they are bacilli, cocci or spirilli. Perhaps Figures 17c and d in your Photo Atlas can be of assistance.}

b. Select a slide of the cyanobacteria Nostoc. Examine it carefully on high power, using your mechanical stage to move the slide slowly about. Assisted by the photomicrographs of Anabaena, a similar genus, in Figures 16a and b of Perry and Morton, locate the bead-like chains of cells. Note the general size and shape of the individual cells. Can you see anything in the cells? Do they all look alike? You should be able to see some larger, colorless cells. These are termed heterocysts and may function in nitrogen fixation. Can you tell the difference between a colony and a filament? Perhaps you can see the gelatinous sheath secreted by some of the cells.

^{Part II - Kingdom Protista}

Introduction

^{With the exception of members of Kingdom Monera, all organisms are said to be eukaryotic. This means that they have a membrane-bounded nucleus and numerous other organelles within the confines of the cell. While most organisms are multicellular, some are not. These are placed in Kingdom Protista. The protists, as they are called, may exist as single, unassociated cells, as colonies with little organization or as rather complex colonies which almost qualify as multicellular organisms.}

Though small, the protists are often quite complex. Several modes of locomotion are found among members of Kingdom Protista and both autotrophic and heterotrophic forms abound. For convenience we will divide the kingdom into two groups, based primarily on their mode of nutrition.

^{A. The Animal-like Protists are often called protozoans. These organisms ingest their food in animal-like fashion. There are four phyla within this group, the names of which come from their method of locomotion.}

1. The flagellates move by means of thin, whip-like flagella. Although some may possess multiple flagella, most have only one or two. These are the most primitive protozoans and the other groups were probably derived from them. Most flagellates are free-living (not parasitic), however, some are important human pathogens. Trypanosoma, for example, causes African sleeping sickness and Giardia has contaminated even the most pristine surface waters in the United States, rendering it undrinkable without treatment.

_{2. The ciliates are the most complex of protozoans. They move by the coordinated rowing motion of many cilia. These are similar in construction to flagella, but are much shorter. Most ciliates are free-living predators or scavengers, inhabiting ponds or temporary pools. These organisms, unlike any others, have two different nuclei. A tiny micronucleus guides the cells reproductive activities, while a much larger macronucleus contains information for all other functions. There is more diversity in form and function in this group than in any other protozoan taxon.}

_{3. The amoebae and their kin are distinguished by their pseudopodia. These are temporary outgrowths of protoplasm with which the creatures feed and/or move. Some members of this group secrete tiny shells, or form one by sticking microbits of sand together. Most, however, are naked. The best place to find these protozoans is in the bottom mud of shallow freshwater pools, but a few are important pathogens of animals, causing gum disease, encephalitis and dysentery.}

_{4. The sporozoans have no mode of locomotion. They don't need one. These are blood parasites which are passed from one host to another by an insect vector -- usually the mosquito. The disease malaria is caused by a sporozoan.}

_ACTIVITIES

_{c. Carefully bring a slide of Trypanosoma into focus on high power. This tiny parasite (usually stained purple) is shown among the pink-staining red blood cells. Can you locate its nucleus and its flagellae?}

d. Select a prepared slide of Paramecium. Find a good specimen and examine it under high power. Using the photos in Figures 22e and f of Perry and Morton, see if you can find the macronucleus and the micronucleus. To observe live Paramecium (if available), prepare a wet mount by placing a drop of the Paramecium culture inside a thin ring of Protoslo as directed by your instructor. This will slow these very active creatures enough to allow their observation.

^{e. Examine a prepared slide of Amoeba proteus. Compare it with Figure 22a in the Photo Atlas. Can you identify the pseudopodia? The nucleus? If live aoebae are available, make a wet mount as directed by your instructor and observe these interesting creatures. Can you see the protoplasm streaming into the pseudopodia? Perhaps you can see this protist capture and ingest a food item of some sort.}

^{B. The plant-like protists are all photosynthetic. In some cases, the exact place of some taxa in our classification is rather vague. That is to say, the exact point at which an "organism" ceases to be a colony of unicells and becomes a single, multicellular creature is not clear. Never-the-less, we will recognize four groups in this category.}

1. The euglenoids are often classified with the flagellates due to their mode of locomotion, yet they are photosynthetic organisms. Not only that, but they store food in a decidedly plant-like form --starch. Euglena, one of the most common laboratory organisms, is in this group.

2. The diatoms are a group which is found in both fresh and salt water. Their delicate valves (shells) are constructed of silicon dioxide -- glass. These protists store their food reserves as oil and may be a major source of our natural petroleum. More importantly, these organisms form the base of the oceanic food chain. Due to the presence of certain accessory pigments in addition to the chlorophyll, the diatoms are a golden color, rather than green.

3. The dinoflagellates are, like the euglenoids, photosynthetic organisms which move with flagella. In this organism, however, one of the flagella is located in a groove around the "waist" of the cell. Some of these protists secrete a tiny shell, while others are naked. Among the dinoflagellates are some which have the ability to create light, rather like a diminutive lightning bug. This phenomenon is termed bioluminescence. The dinoflagellates, unfortunately, also cause "red tides". Here a population explosion results in enough cells to turn the water blood red. These dense populations deplete the water of oxygen and lead to the deaths of thousands of fish.

4. The primitive green algae are placed here for lack of another "pigeon hole" in which to place them. They bear much resemblance to the multicellular green algae, yet many are clearly unicellular. Some of the colonies developed by these protists, are probably the most complex organisms in the entire Kingdom Protista.

^ACTIVITIES

g. Place a slide of Euglena on your microscope and observe these organisms under high power. Can you see the flagellum? Using Figure 18d in Perry and Morton, try to locate the eye spot, the nucleus and the chloroplasts. If live Euglena are available, make a wet mount using Protoslo as directed in Exercise d above. Select a slow-moving specimen and find the parts mentioned above.

_{h. Next select a slide of Diatoms and examine it at high power. You may have to close down your iris diaphragm to see these glass-shelled organisms. Compare these to the photomicrographs on page 20 in the Photo Atlas.}