AP Biology Five Kingdoms of Cells Name_____________________ Per._______ The compound microscope is probably one of the most useful tools available to biologists. Many discoveries have been made in the past through its use. During this laboratory activity you will learn about the microscope, its proper use and care, and certain basic skills and techniques needed to make your microscopic work more efficient. In addition, you will look at cells from each of the five kingdoms of living things and make comparisons about cellular structure. I. Parts of the Microscope: A. ocular (eyepiece) – consists of a set of lenses at the top of the microscope. The magnification of the ocular is stamped on the lens. For example, a lens marked 4X has 4 times the magnification and makes the objects seen through it look four times their actual size. B. Body tube assembly – a hollow tube through which light passes from the objectives on the bottom to the ocular on the top. C. Revolving nosepiece – holds the three or four set of lenses (objectives). As you turn the nosepiece it clicks into different positions, which indicates when each objective is properly aligned for viewing. D. Objectives – the most delicate and costly parts of your microscope. Lower power objective (shortest) magnifies 4x (scanning) Medium power objective magnifies 10X – great detail High power objective (longest) magnifies 40X – greater detail E. Mechanical Stage – holds and supports the microscope slides and some microscopes include a stage back and forth travel knob and a stage lateral travel knob. F. Diaphragm – controls the amount of light that illuminates the viewed object. G. ARM – supports the upper parts of the microscope and provides a handle to carry the microscope. H. Base – the flat bottom part upon which the microscope rests I. Light source – an attached lamp that directs a beam of light up through the object J. Coarse adjustment knob – used to bring objects into focus, used only with low power objective K. Fine adjustment knob – used to bring objects into final view II. How to Focus the Microscope – Low Power • With the coarse adjustment knob, raise the nosepiece until it stops. • Place a slide on the stage and use the clips to secure it. Center the slide as best you can on the stage. • Using the 4X objective, decrease the distance between the stage and the nose piece until the nosepiece is about 1/8 inch above the slide • Look into the ocular, and adjust the diaphragm to give the maximum amount of light. • Use the course adjustment knob and bring the slide into focus • Once the object is seen, it may be necessary to adjust the amount of light using the diaphragm. This can also create shadows. • Use the fine adjustment knob to sharpen the focus. III. How to Focus the Microscope – High Power Compound light microscopes are parfocal – meaning that once an object is in focus with low power, it should be in focus with high power. • Bring the slide into focus under low power by following the previous instructions. • Move the 10X objective into place by turning the nosepiece. • if any adjustment is needed, use only the FINE adjustment knob. High powered objectives are to only be used with the FINE adjustment knobs. • Move the 40X objective into place by turning the nosepiece. • Adjust and focus the e using only the FINE adjustment knob. • When you are finished observing the slide, rotate the nosepiece until the low power objective (4X) clicks into place and then remove the slide from the stage. • Always leave your microsope in low power and be sure to turn off the light. “lights off, low power” IV. The following Rules should be observed: • Have both eyes open when looking through the eyepiece. • The low power objective should be in position at the beginning and the end of each use. • Use only lens paper to clean the lens. • Do not tilt the microscope. • Keep the stage clean and dry to prevent rust and corrosion. • Do not remove parts of the microscope. • Keep the microscope dust free by covering it. • Report any malfunctions immediately. Do not try to repair microscopes on your own. V. Cell Structure Making a wet mount It is often necessary to prepare a specimen for observation under a microscope. The object should be viewed as a wet mount. To prepare a wet mount place it directly on the slide and add a drop of water or stain. The mount is then covered with a cover slip. The cover slip helps contain the specimen and keep the objective lenses clean. •
VI. Investigating Cell Structure 1. Kingdom Monera -­‐bacteria Make a wet mount slide of yogurt. Look for bacteria cells on high power. Draw the cells you see. Yogurt is milk being eaten by bacteria. Don't confuse milk solids with the tiny cells you are looking for. What shapes are the cells? What is their approximate size? How can you tell them from other cells? 2. Kingdom Fungi Make a wet mount slide of yeast cells. Look at them on high power. Draw what you see. Try adding a little "congo red" to the slide. Do you notice any difference with the stain? *What shape are they? How big are they? What organelles can you see? How can you tell them from other cells? 3. Kingdom Protista-­‐ Make a wet mount slide of paramecium by doing the following: •
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Add a “toothpick drop” of stained yeast to your slide-­‐spread it around (you don’t want a puddle of yeast...but a nice thin layer on the slide) Add a very small bit of cotton fibers to the yeast (this will trap the paramecium so that you can view them). Bring this slide to Ms. Kittay who will go “fishing” for you and put some paramecium on your slide. Draw what you see. Describe their movement. What happens when they bump into a cotton fiber? What property of life is this? Can you see the cilia? What cell structures make up these features? Is this organism eating? How do you know? Can you see food vacuoles? What color(s) are they? What does this mean is happening? Can you see a contractile vacuole? What does it seem to be doing? Why is this organelle necessary for the paramecium’s survival ? 4. Kingdom Animalia Now it is time to observe your own cells, squamous epithelium cells from the lining of your cheek. Gently scrape the inside of your cheek with a clean, flat toothpick and place the scraping into the drop of water on the slide and add a drop of very weak methylene blue and add a cover slip. Observe under the microscope with low power. You may have to search for your epithelial cells, but should be easy to find. When they are located, switch to high power and observe the plasma membrane, cytoplasm, and nucleus. Is a nucleolus present? Draw and label what you see. What shape are these cells? What organelles can you identify? How do they differ from plant and fungus cells? Do you store starch in your cheeks? 5. Kingdom Planatae-­‐ •
Place a SINGLE bright green elodea leaf on a slide and add 1 drop of water. Look at the edge of the leaf on medium or high power. Draw what you see. What shape are these cells? What organelles can you see? Are the chloroplasts moving? How big are the chloroplasts in comparison to the cell? •
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Once you have looked at the elodea in a fresh water environment, carefully place 1/2 drops of salt water at the edge of the cover slip and using a piece of paper towel draw the salt water into the slide. Have your partner do this so that you can continue to watch the cells as this is happening (then do the same for your partner!). You have created a hypertonic environment. What happened to the cells in this hypertonic environment? Explain why! Analysis: 1. Total Magnification Ocular Lens Objective Lens Lower Power ______________X _______________= Medium Power ______________X _______________= High Power ______________X _______________= Total Magnification ______________ ______________ ______________ 2. What are the differences between plant and animal cells? PLANT CELL ANIMAL CELL Shape Cell Wall Other 3. What are the differences between a yeast cell (Fungi) and a paramecium (Protist) YEAST CELL PARAMECIUM Shape Cell Wall Other 4. How are the bacteria cells you observed different from all of the other cells you observed in this lab? 5. LABEL THE MICROSCOPE