Comparing Protists




Дата канвертавання27.04.2016
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Biol 11 Comparing Protists


Pre-lab discussion:

Kingdom Protista includes algal protists, animal-like protists, and fungal protists. Protists are often thought of as simple organisms, but a closer examination reveals that they possess a variety of specialized structures. Protists are eukaryotic, which means they have a nucleus enclosed in a membrane. Protists also possess other organelles that perform different functions. Although most protists are one-celled organisms, a few are multicellular. Protists are usually found in damp or watery environments.

In this investigation, you will study several algal and animals-like protists.


Purpose: To determine some characteristics of Paramecium, Euglena gracilis, Amoeba proteus, and Stentor coeruleus.
Materials:

Culture of: A. Pamecium caudatum



B. Euglena gracili,

C. Amoeba proteus

D. Stentor coeruleus.

Microscope

Glass slides

Coverslips

Methyl cellulose

Index card



Toothpick
Safety: Put on a laboratory jacket if one is available. Handle all glassware carefully. Always use special caution when working with laboratory chemicals, as they irritate the skin or cause staining of the skin or clothing. Never touch or taste any chemicals unless instructed to do so. Always handle the microscope with extreme care. You are responsible for its proper care and use. Use caution when handling glass slides as they can break easily and cut you. Note all safety symbols next to the steps in the Procedure.
Procedure:

Part A: Observing Euglena (phylum Euglenophyta)

  1. Prepare a wet-mount slide of the Euglena gracilis culture. Add a drop of methyl cellulose to the culture before placing the cover-slip on the slide. Methyl cellulose will slow down the euglena’s movement. CAUTION: Be careful not to spill the methyl cellulose, It can irritate your skin.

  2. Mount the slide onto the microscope and focus under low power. Locate several euglenas.

  3. Switch to high power and focus on one euglena. Observe the shape of the euglena and distinguish its anterior (front) end from its posterior (rear) end.

  4. Place a drop of immersion oil on the slide and observe the euglena under the oil immersion lens.

  5. Note the chloroplasts, which are greenish structures and that enable a euglena to make its own food.

  6. Locate the euglena’s outer covering or pellicle. The pellicle is flexible and allows the euglena to change its shape. Notice the two flagella, or tail-like structures. The longest flagellum helps the organism move. Find the flask-shaped groove called the reservoir, where the flagella are attached.

  7. Find the contractile vacuole, which collects extra water and discharges it from the cell. Locate the nucleus.

  8. Locate the red eyespot, which is sensitive to light. From an index card, cut a strip the size of a glass side. Then cut a slit about 1.5mm long in the centre of the card. Place the card with the slit under the slide on the microscope stage. After several minutes, carefully remove the card and examine the euglenas again, Answer question 2 in Observation.

  9. In the appropriate place in observation, draw a label one euglena. Label the following parts: pellicle, flagellum, reservoir, chloroplasts, contractile. Vacuole, eyespot, and nucleus. Record the magnification of the microscope.

Carefully wash and dry your slides, cover-slips and wipe the oil off of the oil immersion lens using LENS PAPER.
Part B: Observing Paramecium caudatum (phylum Ciliophora)

  1. Prepare a wet-mount slide of Paramecium caudatum culture. Add a drop of methyl cellulose to the culture before placing the cover-slip on the slide. Methyl cellulose will slow down the Paramecium’s movement. CAUTION: Be careful not to spill the methyl cellulose. It can irritate your skin.

  2. Observe the paramecium under the low-power objective of a microscope.

  3. Switch to a high-power objective and focus on one individual paramecium.

  4. In the appropriate place in observations, draw a sketch of paramecium that you observed. Record the magnification of the microscope.

  5. Look at the movement of the paramecium. Answer question 1 in Observation.


Part C: Observing Amoeba proteus. (phylum Sarcodina)

  1. Using well-slides prepare a wet-mount of Amoeba proteus culture.

  2. Mount the prepared slide under the microscope and focus under low power. Use the diaphragm to cut down the amount of light entering the lens. An Amoeba is easier to observe in low light. Move the slide back and fourth to search for the organism. Amoeba are somewhat transparent and very irregular in shape.

  3. Locate one amoeba and switch to high power. Observe the organism closely for several minutes. Locate the two kinds of cytoplasm: endoplasm, a clear outer layer near the cell membrane; the ectoplasm the granular interior cytoplasm that contains organelles.

  4. Notice the movement of the amoeba’s cytoplasm. Classified as a sarcodine, the amoeba moves with pseudopodia (false feet), or cell extensions.

  5. Observe the organelles such as the nucleus and the contractile vacuole.

  6. Carefully remove the cover-slip from the slide and add a drop of Stentor culture. Mix the two cultures with a toothpick and carefully replace the cover-slip. Observe what happens when an amoeba comes in contact with a Stentor.

  7. In the appropriate place in Observations, draw and label one amoeba. Label the following structures: ectoplasm, endoplasm, pseudopod, nucleus, contractile vacuole, and food vacuole. Answer questions 3 and 4 in Observations.


Part D: Observing Stentor coeruleus

  1. Prepare a wet-mount slide of Stentor coeruleus culture.

  2. Mount the slide under the microscope and focus under low power. Examine the size and shape of the Stentor.

  3. Switch to the high-power objective. Notice the narrow posterior end of the Stentor. It may be attached to debris or algae particles. Normally the organism is free-swimming, but when feeding it attaches its posterior end to an object.

  4. Locate the hair-like cilia. The Stentor is a ciliate protist that moves by means of cilia. Observe the organism for a few minutes. Notice if it changes shape.

  5. Note the shape and location of the mouth opening and the cilia that surround the mouth. The Stentor sucks in food by setting up water currents with these cilia.

  6. Find the gullet, where food is taken into the organism. Also locate the long thin nucleus.

  7. In the appropriate place in Observations, draw and label one Stentor. Label the following structures: cilia, gullet, and nucleus.

  8. Carefully wash and dry your slides and cover-slips.


Observations:





Paramecium Euglena




Amoeba Stentor

Discussion Questions:


  1. Describe any kind of paramecium movement that you discovered.

  2. Where did you find the euglenas after removing the index card?

  3. Does an amoeba retain a constant shape? Explain your answer.

  4. Describe what happens when an amoeba meets some food.

  5. Which protist moved the slowest?

Analysis and Conclusions


  1. How do the eyespot and the chloroplasts work together to help the euglena survive?

  2. What characteristics of an animal does the euglena possess?

  3. What are the functions of cilia in Stentor?

Critical Thinking and Application


  1. Some of the white blood cells in your body show ameboid movement. What does this mean?

  2. Why is it important for a photosynthetic organism such as a euglena to live near the surface of a body of water?

  3. Euglenas are generally autotrophic organisms. Why does this characteristic make the euglena a good choice for use in the biology laboratory?


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