Exercise 1: A Bean Water Micro-community

Note: Bean water incubation requires at least 3 days. Plan accordingly. You will need: Table shown below to record observations, six beans, 50 mL beaker, and tap water. After incubation, a clean slide, eye dropper from dissection kit, drop of bean water, toothpick, heat source,crystal violet stain, staining tray, glass of water, work area protected from staining and microscope.

PROCEDURE:

1. Set up the following table to record observations for Exercise 1 and Exercise 2.Organisms in Micro communities Organism Bean water Pondwater Motile or sessile(reason)Producer or consumer(reason)2. Place six beans from the experiment bag in the 50-mL beaker and half-fill it with tapwater. Allow the beaker to stand in a warm place for 3 to 4 days. Good locations include the kitchen near the stove and a utility room near a hot water heater.

3. Prepare and stain a slide of the bean water. To do this, after the beans have been in the water for several days, dip the clean eyedropper into the bean water and place as mall drop of bean water on a blank microscope slide. Spread the drop with the toothpick until it is about 2 mm in diameter.

4. Light a candle or ignite a long kitchen match or lighter to dry the bean-water slide. Use the test tube clamp to hold the slide by one end in a horizontal position with the spot of bean water on top. Gently pass the slide through the flame several times. This process is called“fixing” the specimen and sticks the cells in the bean water to the slide. Do not heat the slide after the water has evaporated or pass it through the flame so slowly that soot can accumulate on the bottom of the slide. But if the latter happens, you can clean the bottom of the slide with a damp tissue.

5. Continue to hold the hot slide with the test tube clamp. Have a glass with clean water by the sink or basin where you’reworking. Also have a clock or watch with a second hand nearby. Hold the slide over the staining tray with the test tube clamp. Place a few drops of crystal violet stain on the dried bean residue on the slide. Be careful not to spill the crystal violet outside the staining tray as it is a very strong stain. Staining the slide will make the microorganisms from the bean water have more contrast and easier to see.

LabPaq: BK-101 Page 696. After one minute, rinse the excess stain off of the slide by dipping it into the glass of water. Gently shake excess water from the slide into a staining tray, and allow the slide to air-dry.

7. View the dry slide directly with your microscope; no slide cover is required. Draw what you see. Use the chart of microorganisms at the end of the experiment to identify what you draw. List the organisms you observe in the table you’ve made.

Explain your reasons for each identification.A. Next, make a wet-mount slide of the bean water. Place a tiny drop of the beanwater on a blank slide and carefully add a cover slip by touching it to the edge of the drop and lowering the cover slip slowly. Check carefully for organisms. If none seem visible, put a drop of crystal violet on the tip of a toothpick. Shakemost of the crystal violet off the toothpick into the staining tray. Gently lift the cover slip and place the toothpick tip covered with crystal violet into the beanwater on the slide. Such a small amount won’t color the water but it will stain the organisms and help you see them more easily.B. View the wet-mount slide with your microscope and draw what you see. Use the following chart of microorganisms to identify organisms. List the organisms youobserve in the table. Explain your reasons for each identification.C. Determine if each organism is motile or sessile.D. Determine if each organism is a producer or a consumer.

Exercise 2: A Pond or Stream Water Micro community You will need: Plastic funnel, disposable gloves, lab apron, coffee filter, blank microscope slides,microscope slide covers, crystal violet stain, toothpick, pond or stream water, glass jar- pint-size or larger,safety goggles and microscope.

PROCEDURE:

1. Wear your laboratory apron and disposable rubber gloves to collect a sample of water from a pond or slow moving stream in a pint-size or larger glass jar. The source does not need to be of drinkable quality. In fact, a still or even stagnant source may have a richer micro-community provided there are no contaminants in the water such as oil or chemical pollutants that might kill the microorganisms. You should wear your safety goggles when handling this pond water sample since you don’t know what it contains.

2. If you cannot find any surface water, fill a quart or larger container or a bucket with distilled water or well water, not water that contains chlorine, add a handful of rich natural soil, some leaves or other natural materials you find in your yard, stir, let it sit for a week, and draw your sample from that water.

LabPaq: BK-101 Page 703. Place a coffee filter inside the mouth of the funnel. Place the funnel in a small cleang lass that will suspend the funnel and keep it from falling over but is large enough to hold half a cup of liquid below the funnel mouth,4. Fill the 50-mL graduated cylinder with the collected pond water and slowly pour the water sample through the filter. Repeat so that at least 100 mL of pond water passes through the filter

.5. Remove the coffee filter from the funnel after all the water sample has drained through it. Observe if there are any organisms large enough to see without magnification on the filter paper. Quickly draw them for later identification. Turn thecoffee filter inside out and touch the moist tip area with the most collected residue from the pond water to a clean glass slide. If the slide is dry, add a drop of pondwater. Carefully apply a cover slip.

6. Place the wet mount slide under the microscope. Draw what you see. Use the chart of microorganisms at the end of this experiment to identify organisms; you can alsocheck the websites previously listed for other identification keys for the organisms.List the organisms you observe in the table. Explain your reasoning for each identification. If organisms are difficult to see, refer to step #6 in Exercise 1 and use a tiny amount of crystal violet on a toothpick to stain the organisms so they’ll show up more clearly.7. Determine if each organism is motile or sessile, and if each organism is a producer or a consumer.

LabPaq: BK-101 Page 71LabPaq: BK-101 Page 72Questions: A. What are possible sources of the microorganisms in the bean water? B. Explain the color differences between the producers and the consumers. C. Are most organisms in the bean water producers or consumers? Are most organisms in the pond water producers or consumers? D. Are most producers motile or sessile? Are most consumers motile or sessile? E. Explain the overall differences between the two environments.