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LAB 10 MONERA AND PROTISTA PROTOZOANS
The kingdom Monera (Mon'er-a) is comprised of the simplest of all known organisms: the primative bacteria, Archaebacteria, and the true bacteria, Eubacteria, which includes the cyanobacteria (formerly the blue-green algae). The monerans are prokaryotic (pro = before; karyo = nucleus) meaning that their genetic material is not consolidated in a nucleus. This is the singular requirement for membership in the kingdom: the lack of a true nucleus.
The monerans have always been and will continue to be of great importance to human societies. Bacteria are used commercially in the production of dairy products, vinegar, chemicals, and antibiotics. Bacteria cause devastating diseases, food spoilage, food poisoning, and severe agricultural damage. Blue-green algae are responsible for forms of water pollution that may cause disease or death in fish, livestock, and humans. If, however, all monerans on earth were eliminated, the plants and animals would soon die, for they produce the ammonium and nitrates needed by higher plants, and they play a major role in recycling nutrients. Monerans, either directly or indirectly, influence the survival of life on our planet.
Most of the monerans are unicellular organisms, although they frequently occur as filaments or colonies of independent cells. Mitochondria, lysosomes, plastids, Golgi bodies, and endoplasmic reticulum and other membrane organelles are absent. They do possess a cell wall, but it is structurally and chemically different from the cell wall of higher plants. Nutrition of the monerans is primarily through absorption, although some are photosynthetic or chemosynthetic. Reproduction is accomplished through asexual budding or fission; a few species reproduce sexually.
The kingdom Protista (Pro'tist"a) contains diverse groups of organisms that do not fit into any of the other four kingdoms. In fact, the kingdom Protista was originally devised when taxonomists identified "misfit" organisms that were clearly neither plant nor animal. Some protists are actually less closely related to each other than to certain members of the other four kingdoms.
Protists are eukaryotic (eu = true; karyo = nucleus) and characteristically unicellular although some form simple colonies. Their simplicity is misleading for they possess a high degree of specialization at the cellular level. The independent cell performs all the necessary life functions usually accomplished by highly specialized multicellular organs in many complex organisms.
The simple unicellular and filamentous algae are photosynthetic, with chloroplasts, large water vacuoles, and cell walls; they undoubtedly resemble the ancestors of the plant kingdom. Protistan and complex algae will be studied in lab next week. The focus of this lab is the protozoan protists who lack chloroplasts and cell walls and ingest their food; they are probably much like the ancestors of animals. It is in the colonial protists that we have the first indication of division of labor among cells.
Question 1: Name the two divisions of organisms belonging to the kingdom Monera and the common characteristic shared by these groups.
Question 2: Why are monerans an indispensable component of our world?
Question 3: Describe the following moneran characteristics: Cell Arrangement - Cell Wall - Membrane Organelles - Mode of Nutrition - Reproduction -
Question 4: What is the relationship between the members of the kingdom Protista and the members of the other four kingdoms?
Question 5: What is meant by the statement: "Protists possess a high degree of cellular specialization"?
Question 6: Briefly describe the characteristics of the "plant-like" and the "animal-like" protists.
LAB OBJECTIVES:
1. To be familiar with the major and/or unique characteristics of selected members in the primary taxa of the kingdoms Monera and Protista. 2. To identify the living and preserved moneran and protist specimens presented in this lab.
I. Kingdom Monera
A. Division Eubacteria (U-bak-ter'-ea) [true bacteria]
The ubiquity of bacteria is renown, for they are more numerous and more widely distributed in nature than any other group of organisms. They are found in every habitat from the sea floor to icebergs and hot springs.
Prokaryotes range in size from 0.2 to 10 microns [micron (um) = 0.001 mm]. Few eukaryotes are smaller than 7 microns in diameter. Most bacteria fall within a range of 0.2 to 2.0 microns; the designation, microorganism, is appropriate. Refer to figure 1a for the comparative sizes of some selected microorganisms.
Bacterial cells occur in three basic shapes: the spherical coccus (plural cocci = berries), the rod-shaped bacillus (plural bacilli = little staffs), and the spiral shape spirillum (plural spirilla = coils). In some bacteria, the cells fail to separate after division resulting in various colonial arrangements. Each cell in the colonial arrangement, however, still functions as an independent organism and maintains the ability to carry out all processes necessary for survival.
Question 7: What is your interpretation of the word "ubiquity"?
Question 8: Define micron. Into what size range do bacteria fall?
ACTIVITY:
1. Obtain a prepared slide labeled "bacterial types". Notice that the smear is divided into three regions. Examine all three regions microscopically under 40X. These bacterial cells are extremely small and patience is required to bring them into focus. It may be helpful to adjust the light to its lowest setting.
Draw a few of the cells visible in each of the three regions. Label the cells according to their shape. Refer to figure 1b.
Question 9: Name and describe the three basic bacteria shapes.
B. Cyanobacteria (Si'an-o-bak-ter'ea) [blue plant] - the blue-green algae
The cyanobacteria represent the simplest and most primitive plant relative possessing chlorophyll. All species are photosynthetic. Unlike other photosynthetic organisms, they contain only one type of chlorophyll, chlorophyll a, and the pigment is not localized in plastids. The characteristic color of some members results from a mixture of chlorophyll a and a blue pigment, c-phycocyanin.
Members of the phylum exhibit either the primitive unicellular condition or colonial arrangement including filaments, plates, spheres, or clusters. In addition to vegetative cells, a filament may contain heterocysts (hetero = other; cyst = bag). A heterocyst is a very large cell the primary responsibility of which is nitrogen fixation, the process by which gaseous nitrogen from the air is reduced to produce ammonia for use by photosynthetic organisms in synthesizing amino acids. Reproduction is accomplished by simple fission or fragmentation; sexual reproduction is unknown in the phylum.
The cyanobacteria are of great ecological significance. They are important members of the phytoplankton (phyto = plant; plankton = wanderer) that float near the surface of oceans, lakes, and ponds. An important link in the food chain, they provide food for heterotrophs as well as producing oxygen as a by-product of photosynthesis. Conversely, they are common nuisances inhabiting surface waters. Population explosions of blue-green algae are one of the more unpleasant effects of water pollution. The abundant growth results from nutrients, especially phosphates and nitrogen, in sewage, organic wastes, and industrial pollutants which are dumped into the waterways. The surface mats of blue-green algae prevent light from penetrating the water and consequently, severely decrease oxygen production. Additionally, death of the algae provides nourishment for vast numbers of bacteria that decrease the oxygen supply further resulting in fish kills and death of other aquatic animals. They affect the taste and odor of water, clog filters and pipes, and produce toxic wastes. Ironically, the problems arising from population explosions often result directly from our technology and negligence, namely pollution.
Question 10: What is responsible for the characteristic blue-green color in some cyanobacteria?
Question 11: What is nitrogen fixation and what cell in some cyanobacteria performs this function?
Question 12: Of what benefit are phytoplankton?
Question 13: Ecologically, how do population explosions of cyanobacteria affect our waterways?
ACTIVITIES:
1. Prepare a temporary wet mount of Nostoc adding a coverslip. Examine the filaments on 10X. Notice that the cells are strung together like beads. Make sure that you can locate and identify heterocysts. Refer to figure 2.
Draw a Nostoc filament and label the heterocyst.
2. Examine the prepared slide of Nostoc.
II. Kingdom Protista
A. Phylum Zoomastigina (Zoo-mas'ti-ge"na) [animal whip bearer] - the flagellated protozoans (formerly mastigophora)
The unicellular protozoans of this phylum lack cell walls and chloroplasts. Locomotion is accomplished by undulating movements of one or more flagella. Members are either free-living in fresh water, parasitic, or mutualistic organisms which live in close association with members of another species. The phylum includes mutualistic symbionts in the guts of termites and wood roaches; the flagellates digest the cellulose eaten by the insects and transform it into a usable form for the insect. The relationship is truly mutualistic; if deprived of the protozoan, the insect dies. When removed from the insect intestine, the flagellated protozoan also dies. Refer to figure 3.
One parasitic flagellate of great medical importance, Trypanosoma, is responsible for African sleeping sickness. Related flagellates produce similar diseases in cattle. Sleeping sickness is transmitted to the mammalian host by the bite of the tsetse fly, the host during part of the complex life cycle.
Question 14: What is symbiosis? Give an example of mutualistic symbiosis.
ACTIVITY:
1. Obtain a prepared slide labeled "Trypanosoma gambiense". Examine the slide on 40X. Refer to figure 4.
Your instructor will help you label important structures in the figures below.
Draw a Trypanosoma cell. Label the flagellum.
B. Phylum Ciliophora (Si'li-a-for"a) [eyelash] - the ciliated protozoans
These ciliates are extremely complex and are considered to be the most highly specialized protozoans. They lack chlorophyll and are therefore exclusively heterotrophic. Cilia are found covering the entire body or in specialized areas of the cell surface. The body wall contains a thick elastic pellicle in addition to the plasma membrane. Inside the pellicle are numerous trichocysts, threadlike organelles that can be discharged to the outside. Some trichocysts have barbed tips and eject poison; they serve for anchorage, defense, and prey capture.
A peculiar characteristic of the ciliates is the possession of two nuclei. The micronucleus contains one copy of the genetic material and controls sexual reproduction and heredity. The macronucleus controls cell growth and metabolism; it contains up to 500 times as much DNA as the micronucleus. Ciliates are found in fresh and marine water; a few species are parasitic in humans.
Question 15: What are trichocysts? What are the functions of trichocysts?
Question 16: What are the functions of the micronucleus and macronucleus?
Question 17: Why do you suppose the ciliates are considered to be the most highly specialized protozoans?
ACTIVITIES:
1. On a clean glass slide, make a thin Protoslo ring about 1/8 inch in diameter. Place a drop of Paramecium culture in the center of the ring. Slowly lower a coverslip into place. Examine your mount on 10X until you've located a Paramecium. At either end of the cell specialized vacuoles, contractile vacuoles, should be visible. Water enters the cell by osmosis, and the contractile vacuoles pump out excess water. Observe the canals radiating outward from each vacuole. Note the time interval between each contraction. Refer to figure 5 and locate the labeled organelles.
Question 18: What can be noticed about the time interval between the contractions of the contractile vacuoles?
2. Add a small drop of methyl green at the edge of the coverslip. Allow it to run underneath and observe the discharge of trichocysts.
3. Examine the prepared slide of Paramecium.
C. Phylum Sarcodina (Sar'ko-di"na) [flesh] - the amoeboid protozoans
The sarcodines are exclusively heterotrophic. They lack cilia and flagella. These protists move and engulf their prey with pseudopodia (pseudo = false; poda = foot). In locomotion, the organism extends a pseudopod from any part of the body surface and the rest of the body flows into the forward extrusion.
The sarcodines have no cell wall but some secrete shells containing silica or calcium carbonate. One such group, the foraminiferans, inhabit the warm oceans and secrete a calcareous shell. The shell is full of holes through which they poke long thin pseudopodia. The pseudopodia branch and join outside the shell to form a net that traps and digests the organism's prey. When foraminiferans die, their shells sink to the bottom. Millions of years' of deposits of this debris has formed chalk rocks or limestone such as the white cliffs of Dover, England.
Radiolarians, an exclusively marine group, secrete elaborate and beautiful exoskeletons that usually contain silica. They too extrude pseudopodia through their shell, but unlike foraminiferans, they draw their prey inside the shell for digestion.
Question 19: How is nourishment in foraminiferans and radiolarians accomplished?
ACTIVITIES:
1. Place a drop of Amoeba culture on a clean depression slide. Slowly draw the coverslip into place excluding air bubbles. Examine the slide diligently on 4X and look for an Amoeba. It will be helpful to adjust the light to a low setting because of the organism's transparent nature. The Amoeba will appear as a grayish transparent object of irregular shape. The granular cytoplasm, or endoplasm, contains a nucleus, contractile vacuoles, and possibly food vacuoles. Refer to figure 6.
Switch to 40X and study the Amoeba in detail. The clear outer layer of the organism is ectoplasm and is bounded on the surface by the plasma membrane. The line which you see at the edge of the Amoeba is not the plasma membrane, but an optical effect produced by the difference in density between the ectoplasm and the surrounding water. As the Amoeba moves, observe the inter-conversion of ectoplasm and endoplasm at the advancing tip of a pseudopodium.
2. Examine the prepared slide of Amoeba under 40X.
3. Obtain the prepared slide labeled "Radiolaria". Adjust the light to the middle setting. Examine the slide on 40X scanning all areas of the smear. You are observing the unstained transparent silica exoskeleton. Refer to figure 7.
Draw three different radiolarians.
4. Examine the prepared slide of foraminiferans. Refer to figure 8.
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