Benson microbiological applications lab manual eighth edition

Related Articles:. Home References Article citations. Journals A-Z. Journals by Subject. Publish with us. Contact us. Related Articles: Open Access. Advances in Microbiology Vol. DOI: Open Access. If immersion oil has been used, wipe it off the lens and stage with lens tissue.

Do not wipe oil off slides you wish to keep. Simply put them into a slide box and let the oil drain off.

Rotate the low-power objective into position. If the microscope has been inclined, return it to an erect position. If the microscope has a built-in movable lamp, raise the lamp to its highest position. If the microscope has a long attached electric cord, wrap it around the base. Adjust the mechanical stage so that it does not project too far on either side. Replace the dustcover. If the microscope has a separate transformer, return it to its designated place.

Return the microscope to its correct place in the cabinet. Preparation on your part prior to going to the laboratory will greatly facilitate your understanding.

Your instructor may wish to collect this report at the beginning of the period on the first day that the microscope is to be used in class. Delicate transparent living organisms can be more easily observed with darkfield microscopy than with conventional brightfield microscopy. This method is particularly useful when one is attempting to identify spirochaetes in the exudate from a syphilitic lesion.

Figure 2. This effect may be produced by placing a darkfield stop below the regular condenser or by replacing the condenser with a specially constructed one. Another application of darkfield microscopy is in the fluorescence microscope Exercise 4. Although fluorescence may be seen without a dark field, it is greatly enhanced with this application. To achieve the darkfield effect it is necessary to alter the light rays that approach the objective in such a way that only oblique rays strike the objects being viewed.

The obliquity of the rays must be so extreme that if no objects are in the field, the background is completely light-free. Objects in the field become brightly illuminated, however, by the rays that are reflected up through the lens system of the microscope. Although there are several different methods for producing a dark field, only two devices will be described here: the star diaphragm and the cardioid condenser.

The availability of equipment will determine the method to be used in this laboratory. This device has an opaque disk in the center that blocks the central rays of light. If such a device is not available, one can be made by cutting round disks of opaque paper of different sizes that are cemented to transparent celluloid disks that will fit into the slot.

If the microscope normally has a diffusion disk in this slot, it is best to replace it with rigid clear celluloid or glass. An interesting modification of this technique is to use colored celluloid stops instead of opaque paper.

Backgrounds of blue, red, or any color can be produced in this way. In setting up this type of darkfield illumination it is necessary to keep these points in mind:. Limit this technique to the study of large organisms that can be seen easily with low-power magnification. Good resolution with higher powered objectives is difficult with this method.

Keep the diaphragm wide open and use as much light as possible. If the microscope has a voltage. Be sure to center the stop as precisely as possible. Move the condenser up and down to produce the best effects. Special condensers such as the cardioid or paraboloid types must be used. Since the cardioid type is the most frequently used type, its use will be described here. Note that the light rays entering the lower element of the condenser are reflected first off a convex mirrored surface and then off a second concave surface to produce the desired oblique rays of light.

Once the condenser has been installed in the microscope, the following steps should be followed to produce ideal illumination. Materials: slides and cover glasses of excellent quality slides of 1.

Remove the clear glass slide. If a funnel stop is available for the oil immersion objective, remove this object and insert this unit. This stop serves to reduce the numerical aperture of the oil immersion objective to a value that is less than the condenser.

Place a drop of immersion oil on the upper surface of the condenser and place the slide on top of the oil. Scratches and imperfections will cause annoying diffractions of light rays.

If the oil immersion lens is to be used, place a drop of oil on the cover glass. If contrast is still lacking after these adjustments, the specimen is probably too thick. If sharp focus is difficult to achieve under oil immersion, try using a thinner cover glass and adding more oil to the top of the cover glass and bottom of the slide. Adjust the upper surface of the condenser to a height just below stage level. Place a clear glass slide in position over the condenser.

Center the bright ring so that it is concentric with the field edge by adjusting the centering screws on the darkfield condenser. If the condenser has a. This exercise may be used in conjunction with Part 2 when studying the various types of organisms.

After reading over this exercise and doing any special assignments made by your instructor, answer the questions on the last portion of Laboratory Report 1,2 that pertain to darkfield microscopy. This method requires maximum illumination. The difficulty that one encounters in trying to examine cellular organelles is that most protoplasmic material is completely transparent and defies differentiation.

It is for this reason that stained slides are usually used in brightfield cytological studies. Since the staining of slides results in cellular death, it is obvious that when we study stained microorganisms on a slide, we are observing artifacts rather than living cells.

A microscope that is able to differentiate transparent protoplasmic structures without staining and killing them is the phase-contrast microscope. The first phase-contrast microscope was developed in by Frederick Zernike and was originally referred to as the Zernike microscope. It is the instrument of choice for studying living protozoans and other types of transparent cells. Figure 3. Note the greater degree of differentiation that can be seen inside cells when they are observed with phasecontrast optics.

In this exercise we will study the principles that govern this type of microscope; we will also see how different manufacturers have met the design challenges of these principles. Amplitude objects illustration 1, figure 3. Phase objects illustration 2, figure 3. This retardation, known as phase shift, occurs with no amplitude diminution; thus, the objects appear transparent rather than opaque.

Since most biological specimens are phase objects, lacking in contrast, it becomes necessary to apply dyes of various kinds to cells that are to be studied with a brightfield microscope. Those rays that pass straight through unaffected by the medium are called direct rays. They are unaltered in amplitude and phase.

The balance of the rays that are bent by their slowing through the medium due to density differences emerge from the object as diffracted rays. Illustration 3, figure 3.

An important characteristic of these light rays is that if the direct and diffracted rays of an object can be brought into exact phase, or coincidence, with each other, the resultant amplitude of the converged rays is the sum of the two waves. This increase in amplitude will produce increased brightness of the object in the field.

This phenomenon is called interference. Illustration 4, figure 3. It differs from a conventional brightfield microscope by having 1 a different type of diaphragm and 2 a phase plate. The diaphragm consists of an annular stop that allows only a hollow cone of light rays to pass up through the condenser to the object on the slide.

The phase plate is a special optical disk located at the rear focal plane of the objective. Note in figure 3. These rays emerge as solid lines from the object on the slide. This ring on the phase plate is coated with a material that will produce the desired phase shift. It should be clear, then, that depending on the type of phasecontrast microscope, the convergence of diffracted and direct rays on the image plane will result in either a brighter image amplitude summation or a darker.

The former is referred to as bright phase microscopy; the latter as dark phase microscopy. The apparent brightness or darkness, incidentally, is proportional to the square of the amplitude; thus, the image will be four. It should be added here, parenthetically, that the phase plates of some microscopes have coatings to change the phase of the diffracted rays.

In any event. Although a phase-contrast objective has a phase ring attached to the top surface of one of its lenses, the presence of that ring does not seem to impair the resolution of the objective when it is used in the brightfield mode.

It is for this reason that manufacturers have designed phase-contrast microscopes in such a way that they can be quickly converted to brightfield operation. To make a microscope function efficiently in both phase-contrast and brightfield situations one must master the following procedures:. The following suggestions should be helpful in coping with these problems. Alignment of Annulus and Phase Ring Unless the annular ring below the condenser is aligned perfectly with the phase ring in the objective, good phase-contrast imagery cannot be achieved.

If a microscope has only one phase-contrast objective, there will be only one annular stop that has to be aligned. If a microscope has two or more phase objectives, there must be a substage unit with separate annular stops for each phase objective, and alignment procedure must be performed separately for each objective and its annular stop. Since the objective cannot be moved once it is locked in position, all adjustments are made to the annular stop.

On some microscopes the adjustment may be made with tools, as illustrated in figure 3. On other microscopes, such as the Zeiss in figure 3. Since the method of adjustment varies from one brand of microscope to another, one has to follow the instructions provided by the manufacturer. Once the adjustments have been made, they. To observe ring alignment, one can replace the eyepiece with a centering telescope as shown in figure 3.

With this unit in place, the two rings can be brought into sharp focus by rotating the focusing ring on the telescope. Refocusing is necessary for each objective and its matching annular stop. Some manufacturers, such as American Optical, provide an aperture viewing unit figure 3.

Zeiss microscopes have a unit called the Optovar, which is located in a position similar to the American Optical unit that serves the same purpose. Light Source Adjustment For both brightfield and phase-contrast modes it is essential that optimum lighting be achieved. This is no great problem for a simple setup such as the American Optical instrument shown in figure 3. For multiple phase objective microscopes, however, such as the Zeiss in figure 3. A few suggestions that highlight some of the problems and solutions follow:.

When pushed in, the annular stop is in position. Since blue light provides better images for both phase-contrast and brightfield modes, make certain that a blue filter is placed in the filter holder that is positioned in the light path.

If the microscope has no filter holder, placing the filter over the light source on the base will help. Brightness of field under phase-contrast is controlled by adjusting the voltage or the iris diaphragm on the base. Considerably more light is required for phase-contrast than for brightfield since so much light is blocked out by the annular stop. The evenness of illumination on some microscopes, such as the Zeiss seen on these pages, can be adjusted by removing the lamp housing from the microscope and focusing the light spot on a piece of translucent white paper.

For the detailed steps in this procedure, one should consult the instruction manual that comes with the microscope. Light source adjustments of this nature are not necessary for the simpler types of microscopes. Since each phase-contrast objective must be used with a matching annular stop, make certain that the proper annular stop is being used with the objective that is over the microscope slide. If image quality is lacking, check first to see if the matching annular stop is in position. Keep in mind that from now on most of the adjustments described earlier should not be altered; however, if misalignment has occurred due to mishandling, it will be necessary to refer back to alignment procedures.

The latter leave much to be desired. Culture broths containing bacteria or protozoan suspensions are ideal for wet mounts. In most instances stained slides are not satisfactory. The first time you use phase-contrast optics to examine a wet mount, follow these suggestions: 1. Place the wet mount slide on the stage and bring the material into focus, using brightfield optics at low-power magnification.

Once the image is in focus, switch to phase optics at the same magnification. Remember, it is necessary to place in position the matching annular stop.

Adjust the light intensity, first with the base diaphragm and then with the voltage regulator. In most instances you will need to increase the amount of light for phase-contrast. Switch to higher magnifications, much in the same way you do for brightfield optics, except that you have to rotate a matching annular stop into position. If an oil immersion phase objective is used, add immersion oil to the top of the condenser as well as to the top of the cover glass. Halos are normal.

Organelles in protozoans and algae will show up more distinctly than with brightfield optics. After reading this exercise and doing any special assignments made by your instructor, answer the questions on combined Laboratory Report 3—5 that pertain to this exercise.

The fluorescence microscope is a unique instrument that is indispensible in certain diagnostic and research endeavors. Differential dyes and immunofluorescence techniques have made laboratory diagnosis of many diseases much simpler with this type of microscope than with the other types described in Exercises 1, 2, and 3. In addition, it is important that one be aware of the potential of experiencing eye injury if one of these instruments is not used in a safe manner.

A fluorescence microscope differs from an ordinary brightfield microscope in several respects. First of all, it utilizes a powerful mercury vapor arc lamp for its light source.

The third difference is that it employs three sets of filters to alter the light that passes up through the instrument to the eye. Some general principles related to its operation will follow an explanation of the principle of fluorescence. An interesting characteristic of such an electromagnetic wave is that it can influence the electrons of molecules that it encounters, causing significant interaction.

Those electrons within a molecule that are not held too securely may be set in motion by the oscillations of the light beam. Not only are these electrons interrupted from their normal pathways, but they are also forced to oscillate in resonance with the passing light wave.

This excitation, caused by such oscillation, requires energy that is supplied by the light beam. When we say that a molecule absorbs light, this is essentially what is taking place. This new manifestation of the energy may be in the form of a chemical reaction, heat, or light. If light is emitted by the energized molecules, the phenomenon is referred to as photoluminescence. In photoluminescence there is always a certain time lapse between the absorption and emission of light.

Thus, we see that fluorescence is initiated when a molecule absorbs energy from a passing wave of light. The excited molecule, after a brief period of time, will return to its fundamental energy state after emitting fluorescent light.

It is significant that the wavelength of fluorescence is always longer than the exciting light. This phenomenon is due to the fact that energy loss occurs in the process so that the emitting light has to be of a longer wavelength.

This energy loss, incidentally, occurs as a result of the mobilization of the comparatively heavy atomic nuclei of the molecules rather than the displacement of the lighter electrons. Microbiological material that is to be studied with a fluorescence microscope must be coated with special compounds that possess this quality of fluorescence.

Such compounds are called fluorochromes. Auramine O, acridine orange, and fluorescein are well-known fluorochromes. Whether a compound will fluoresce will depend on its molecular structure, the temperature, and the pH of the medium.

The proper preparation and use of fluorescent materials for microbiological work must take all these factors into consideration. The essential components are the light source, heat filter, exciter filter, condenser, and barrier filter. The characteristics and functions of each item follow. Light Source The first essential component of a fluorescence microscope is its bright mercury vapor arc lamp.

Such a bulb is preferred over an incandescent one because it produces an ample supply of shorter wavelengths of light ultraviolet, violet, and blue that are needed for good fluorescence. To produce the arc in one of these lamps, voltages as high as 18, volts are required; thus, a power supply transformer is always used.

The wavelengths produced by these lamps include the ultraviolet range of — nm, the visible range of — nm, and the long infrared rays that are above nm. Mercury vapor arc lamps are expensive and potentially dangerous. Certain precautions must be taken, not only to promote long bulb life, but to protect the user as well. One of the hazards of these bulbs is that they are pressurized and can explode. Another hazard exists in direct exposure of the eyes to harmful rays.

Knowledge of these hazards is essential to safe operation. If one follows certain precautionary measures, there is little need for anxiety.

However, one should not attempt to use one of these instruments without a complete understanding of its operation. Heat Filter The infrared rays generated by the mercury vapor arc lamp produce a considerable amount of heat.

These rays serve no useful purpose in fluorescence and place considerable stress on the filters within the system. To remove these rays, a heat-absorbing filter is the first element in front of the condensers. Ultraviolet rays, as well as most of the visible spectrum, pass through this filter unimpeded. Exciter Filter After the light has been cooled down by the heat filter it passes through the exciter filter, which absorbs all the wavelengths except the short ones needed to excite the fluorochrome on the slide.

These filters are very dark and are designed to let through only the green, blue, violet, or ultraviolet rays. If the exciter filter is intended for visible light blue, green, or violet transmission, it will also allow ultraviolet transmittance. Condenser To achieve the best contrast of a fluorescent object in the microscopic field, a darkfield condenser is used.

It must be kept in mind that weak fluorescence of an object in a brightfield would be difficult to see. The dark background produced by the darkfield condenser, thus, provides the desired contrast.

Another bonus of this type of condenser is that. Figure 4. To achieve this, the numerical aperture of the objective is always 0. Barrier Filter This filter is situated between the objective and the eyepiece to remove all remnants of the exciting light so that only the fluorescence is seen. When ultraviolet excitation is employed with its very dark, almost black-appearing exciter filters, the corresponding barrier filters appear almost colorless.

On the other hand, when blue exciter filters are used, the matching barrier filters have a yellow to deep orange color. In both instances, the significant fact is that the barrier filter should cut off precisely the shorter exciter wavelengths without affecting the longer fluorescence wavelengths.

Although different makes of fluorescence microscopes are essentially alike in principle, they may differ considerably in the fine points of operation.

Since it is not possible to be explicit about the operation of all makes, all that will be attempted here is to generalize. Some Precautions To protect yourself and others it is well to outline the hazards first. Keep the following points in mind:. Remember that the pressurized mercury arc lamp is literally a potential bomb. Design of the equipment is such, however, that with good judgment, no injury should result. When these lamps are cold they are relatively safe, but when hot, the inside pressure increases to eight atmospheres, or pounds per square inch.

The point to keep in mind is this—never attempt to inspect the lamp while it is hot. Let it cool completely before opening up the lamp housing. Usually, 15 to 20 minutes cooling time is sufficient. Never expose your eyes to the direct rays of the mercury arc lamp. Equipment design is such that the bulb is always shielded against the scattering of its rays. Remember that the unfiltered light from one of these lamps is rich in both ultraviolet and infrared rays—both of which are damaging to the eyes.

Severe retinal burns can result from exposure to the mercury arc rays. Be sure that the barrier filter is always in place when looking down through the microscope. Removal of the barrier filter or exciter filter or both filters while looking through the microscope could cause eye injury. It is possible to make mistakes of this nature if one is not completely familiar with the instrument.

Remember, the function of the barrier filter is to prevent traces of ultraviolet light from reaching the eyes without blocking wavelengths of fluorescence. Warm-up Period The lamps in fluorescence microscopes require a warm-up period. When they are first turned on the illumination is very low, but it increases to maximum in about 2 minutes. Optimum illumination occurs when the equipment has been operating for 30 minutes or more.

Most manufacturers recommend leaving the instruments turned on for an hour or more when using them. It is not considered good economy to turn the instrument on and off several times within a 2- or 3-hour period. Keeping a Log The life expectancy of a mercury arc lamp is around hours.

A log should be kept of the number of hours that the instrument is used so that inspection can be made of the bulb at approximately hours.

A card or piece of paper should be kept conveniently near the instrument so that the individual using the instrument is reminded to record the time that the instrument is turned on and off. Note that the exciter filter gives peak emission of light in the nm area of the spectrum. These rays are violet. It allows practically no green or yellow wavelengths through. The shortest wavelengths that this barrier filter lets through are green to greenish-yellow.

If a darker background is desired than is being achieved with the above filters, one may add a pale blue Schott BG38 to the system.

It may be placed on either side of the heat filter, depending on the type of equipment being used. If it is placed between the lamp and heat filter, it will also function as another heat filter. Examination When looking for material on the slide, it is best to use low- or high-power objectives.

If the illuminator is a separate unit, as in figure 4. Once the desirable field has been located, the mercury vapor arc illuminator can be moved into position.

One problem with fluorescence microscopes is that most darkfield condensers do not illuminate well through the low-power objectives exception: the Reichert-Toric setup used on some American Optical instruments.

Keep in mind that there is no diaphragm control on darkfield condensers. Some instruments are supplied with neutral density filters to reduce light intensity.

The best system of illumination control, however, is achieved with objectives that have a built-in iris control. These objectives have a knurled ring that can be rotated to control the contrast. For optimum results it is essential that oil be used between the condenser and the slide. And, of course, if the oil immersion lens is used, the oil must also be interposed between the slide and the objective.

It is also important that special low-fluorescing immersion oil be used. Ordinary immersion oil should be avoided.

With bright-field microscopes it is generally accepted that nothing is. The only loss by using the higher magnification is some brightness. An ocular micrometer consists of a circular disk of glass that has graduations engraved on its upper surface.

These graduations appear as shown in illustration B, figure 5. On some microscopes one has to disassemble the ocular so that the disk can be placed on a shelf in the ocular tube between the two lenses. On most microscopes, however, the ocular micrometer is simply inserted into the bottom of the ocular, as shown in figure 5.

Before one can use the micrometer it is necessary to calibrate it for each of the objectives by using a stage micrometer. The principal purpose of this exercise is to show you how to calibrate an ocular micrometer for the various objectives on your microscope. Proceed as follows:. A stage micrometer figure 5. Illustration C, figure 5. To calibrate the ocular micrometer for a given objective, it is necessary to superimpose the two scales and determine how many of the ocular graduations coincide with one graduation on the scale of the stage micrometer.

Illustration A in figure 5. In this case, seven ocular divisions match up with one stage micrometer division of 0. Since there are micrometers in 1 millimeter, these divisions are 1. With this information known, the stage micrometer is replaced with a slide of organisms to be measured. Illustration D, figure 5. Figure 5. To determine the size of an organism, then, it is a simple matter to count the graduations and multiply this number by the known distance between the graduations. When calibrating the objectives of a microscope, proceed as follows.

Materials: ocular micrometer or eyepiece that contains a micrometer disk stage micrometer 1. If eyepieces are available that contain ocular micrometers, replace the eyepiece in your microscope with one of them. If it is necessary to insert an ocular micrometer in your eyepiece, find out from your instructor whether it is to be inserted below the bottom lens or placed between the two lenses within the eyepiece.

In either case, great care must be taken to avoid dropping the eyepiece or reassembling the lenses incorrectly. Be sure that the graduations are on the upper surface of the glass disk. Place the stage micrometer on the stage and center it exactly over the light source.

Reduce the lighting. Note: If the microscope has an automatic stop, do not use it as you normally would for regular microscope slides. The stage micrometer slide is too thick to allow it to function properly. Rotate the eyepiece until the graduations of the ocular micrometer lie parallel to the lines of the stage micrometer. If the low-power objective is the objective to be calibrated, proceed to step 8. If the high-dry objective is to be calibrated, swing it into position and proceed to step 8.

If the oil immersion lens is to be calibrated, place a drop of immersion oil on the stage micrometer, swing the oil immersion lens into position, and bring the lines into focus; then, proceed to the next step. Move the stage micrometer laterally until the lines at one end coincide.

Then look for another line on the ocular micrometer that coincides exactly with one on the stage micrometer. Occasionally one stage micrometer division will include an even number of ocular divisions, as shown in illustration A. In most instances, however, several stage graduations will be involved. In this case, divide the number of stage micrometer divisions by the number of ocular divisions that coincide. The figure you get will be that part of a stage micrometer division that is seen in an ocular division.

This value must then be multiplied by 0. Example: 3 divisions of the stage micrometer line up with 20 divisions of the ocular micro-meter. If your instructor requires that measurements be made, you will be referred to this exercise.

Later on you will be working with unknowns. In some cases measurements of the unknown organisms will be pertinent to identification. If trial measurements are to be made at this time, your instructor will make appropriate assignments.

Important: Remove the ocular micrometer from your microscope at the end of the laboratory period. Too often, in our serious concern with the direct applications of microbiology to human welfare, we neglect the large number of interesting free-living microorganisms that abound in the water, soil, and air. It is these free-spirited forms that we will study in the four exercises of this unit. To observe these organisms we will examine samples of pond water and Petri plates with special media that have been exposed to the air and various items in our environment.

The principal organisms that we will encounter are protozoans, algae, molds, yeasts, cyanobacteria, and bacteria. The phylogenetic tree on this page illustrates where these organisms fit in the evolutionary scheme of organisms. The organisms that you are likely to encounter are underlined on the diagram.

A few comments about each domain are presented here. Domain Archaea Since the principal habitats of these organisms are extreme environments such as volcanic waters, hot springs, or waters of high salt conditions, you will not encounter any of these organisms in this study. All members of this domain have distinct nuclei with nuclear membranes and mitochondria. Some eukaryotes, such as the algae, have chloroplasts, which puts them in the plant kingdom.

The eukaryotes appear to be more closely related to the Archaea than to the Bacteria. In this study you will encounter various species of cyanobacteria and bacteria. From: Extremophiles. Michael T. Madigan and Barry L. Marrs in Scientific American Vol.

In this exercise a study will be made of protozoans, algae, and cyanobacteria that are found in pond water. Bottles that contain water and bottom debris from various ponds will be available for study. Illustrations and text provided in this exercise will be used to assist you in an attempt to identify the various types that are encountered.

Unpigmented, moving microorganisms will probably be protozoans. Greenish or golden-brown organisms are usually algae. Organisms that appear blue-green will be cyanobacteria. Supplementary books on the laboratory bookshelf will also be available for assistance in identifying organisms that are not described in the short text of this exercise. If you encounter invertebrates and are curious as to their identification, you may refer to Exercise 7; however, keep in mind that our prime concern here is only with protozoans, algae, and cyanobacteria.

The purpose of this exercise is, simply, to provide you with an opportunity to become familiar with the differences between the three groups by comparing their characteristics.

The extent to which you will be held accountable for the names of various organisms will be determined by your instructor. The amount of time available for this laboratory exercise will determine the depth of scope to be pursued. To study the microorganisms of pond water, it will be necessary to make wet mount slides. The procedure for making such slides is relatively simple. All that is necessary is to place a drop of suspended organisms on a microscope slide and cover it with a cover glass.

If several different cultures are available, the number of the bottle should be recorded on the slide with a china marking pencil. As you prepare and study your slides, observe the following guidelines: Materials: bottles of pond-water samples microscope slides and cover glasses rubber-bulbed pipettes and forceps china marking pencil reference books 1. Clean the slide and cover glass with soap and water, rinse thoroughly, and dry. Do not attempt to study a slide that lacks a cover glass.

When using a pipette, insert it into the bottom of the bottle to get a maximum number of organisms. Very few organisms will be found swimming around in middepth of the bottle. To remove filamentous algae from a specimen bottle, use forceps. Avoid putting too much material on the slides.

Explore the slide first with the low-power objective. Reduce the lighting with the iris diaphragm. Keep the condenser at its highest point. When you find an organism of interest, swing the high-dry objective into position and adjust the lighting to get optimum contrast. If your microscope has phase-contrast elements, use them. Refer to Figures 6. Record your observations on the Laboratory Reports. Protozoologists group all protists in Kingdom Protista. Those protists that are animallike are put in Subkingdom Protozoa and the protists that are plantlike fall into Subkingdom Algae.

This system of classification includes all colonial species as well as the single-celled types. Specialized organelles, such as contractile vacuoles, cytostomes, mitochondria, ribosomes, flagella, and cilia, may also be present. All protozoa produce cysts, which are resistant dormant stages that enable them to survive drought, heat, and freezing.

They reproduce asexually by cell division and exhibit various degrees of sexual reproduction. Type of locomotion plays an important role in classification here.

A brief description of each phylum follows:. Appropriate for either a majors or non-majors lab course, it assumes no prior organic chemistry course has been taken. Read more Please choose whether or not you want other users to be able to see on your profile that this library is a favorite of yours. Finding libraries that hold this item You may have already requested this item. Reference details.

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