PROTISTS INTRODUCTION All organisms that can't be classified as Plants, Animals, Fungi, Archea, or Bacteria are placed in the Kingdom Protista. All Protista are Eukaryotes they possess a nucleus and other internal structures separated by membranes (membrane-bound organelles). Here the similarity among protists ends – members of this group can be unicellular (organisms consisting of only one cell), colonial (groups cells with some interdependence), or multicellular (composed of many cells with coordinated metabolic activity, may form tissues), autotrophic or heterotrophic. Here is a review of the basic classification system used for all living organisms: Type of Cell Domain Kingdom Example Prokaryotic Archaea Not Used Prokaryotic organisms found in extreme environments Prokaryotic Bacteria Not Used common bacteria, cyanobacteria Eukaryotic Eukarya Protists algae, Paramecium, Amoeba, Euglena Eukaryotic Eukarya Fungi mushrooms, mold, Penicillium Eukaryotic Eukarya Animals vertebrates, insects, nematodes, sponges Eukaryotic Eukarya Plants moss, ferns, redwoods, flowering plants There are fossils of protists that are over 2 billion years old, and protists have evolved and diversified since that time. Scientists attempt to classify these organisms according to their evolutionary relationships using evidence from the fossil record, DNA, RNA and other cell structures. The result of this work has led to the proposal of alternative classification systems that may divide the Kingdom Protista into several in the future. For our purposes we will divide the protists according to their mode of nutrition (how they obtain their nutrients and energy) rather than evolutionary relatedness. The protozoa are heterotrophic protists that ingest their food, and are single-celled or colonial. Algae are all photosynthetic autotrophic organisms, these may be unicellular, colonial, or multicellular (filaments or sheets). GOALS AND OBJECTIVES 1. Know the meaning and examples of the vocabulary highlighted in bold. 2. Understand the composition of the Kingdom Protista. What are the main phyla within the Kingdom? 3. Be able to identify the phylum of each protist you observe in lab. 4. Know the special characteristics of each phylum. 5. For each Protist know the method of acquiring food/energy. If the organism is photosynthetic, know the pigments involved. 6. Know the means of locomotion for each type of motile protist. 7. Know the habitat in which each organism is found. 8. Understand the difference between single-celled, colonial, and multicellular. 10.09 5A-1 KINGDOM PROTISTA HETEROTROPHIC PROTISTS PHYLUM CILIATES – Paramecium characteristics: single-celled protists that move by means of cilia. Ciliates, like Paramecium, are heterotrophic and take food into their cell through an oral groove; once inside the cell a food vacuole forms. PHYLUM AMOEBOIDS – Amoeba. characteristics: single-celled protists that move by means of pseudopods, this type of movement causes the shape of an Amoeba’s cell to constantly change. Food is engulfed by pseudopods forming a food vacuole. AUTOTROPHIC PROTISTS PHYLUM EUGLENOIDS – Euglena. characteristics: single-celled protists that possess chloroplasts (containing chlorophyll) and can live either as heterotrophs or autotrophs. Euglena moves by means of flagella; their flexible body also allows them to slowly undulate along surfaces. The Euglena seen in our lab is primarily autotrophic. PHYLUM DINOFLAGELLATES – Ceratium characteristics: single-celled plankton that are important primary producers in freshwater and marine environments. Most possess chloroplasts containing chlorophyll and a yellow-brown accessory pigment, but some are heterotrophic. Dinoflagellates have a cellulose cell wall that consists of overlapping armored plates. They move by means of two flagella, one of which wraps around the center of the cell. PHYLUM DIATOMS - Diatoms characteristics: single-celled plankton that are important primary producers in freshwater and marine environments. Like dinoflagellates, they possess chloroplasts containing chlorophyll and the accessory yellow-brown pigment. The cell walls of diatoms are made of sculptured silica (glass). Most are non-motile, but a few are able to glide along surfaces. PHYLUM GREEN ALGAE – Volvox, Spirogyra, sea lettuce characteristics: single-celled, colonial, or simple multicellular organisms whose green color is the result of the pigment chlorophyll. Green algae are important primary producers in freshwater and intertidal habitats. They can be non-motile, or motile by means of flagella. Cell walls contain cellulose. Green algae are the most likely ancestors of plants. PHYLUM RED ALGAE – Porphyra, coraline red, Microcladia characteristics: multicellular marine organisms that range from filaments to blade-like sheets. They tend to be reddish in color due to an accessory pigment that masks the primary photosynthetic pigment chlorophyll. This accessory pigment allows them to grow in deeper water than other algae. Cell walls contain cellulose. Red algae are non-motile. 10.09 5A-2 PHYLUM BROWN ALGAE – kelp characteristics: large multicellular, marine organisms that have specialized tissues that forms a blade (photosynthesis), holdfast (anchors to substrate), and stipe (connects blade to holdfast, especially important in deep water off the coast), some also have a bladder (floatation). They tend to be brownish in color due to an accessory pigment that masks the primary photosynthetic pigment chlorophyll. Cell walls contain cellulose. Brown algae lack motile adult stages. REVIEW OF SPECIMEN PREPARATION AND MICROSCOPE USE Cultures of living specimens are placed on the side bench for you to examine under the compound microscope. Make wet mounts, cover with a coverslip, and bring back to your station for observation. Some specimens will also be available as prepared slides. You may want to base your drawings on these. Remember the following steps when using compound microscopes: Always start with the 4X objective and the stage at its lowest position Center your slide over the condenser lens and move the stage to its highest position Lower the stage slowly using the coarse focus knob while viewing your slide until objects come into focus Use the stage ( X and Y) control knobs to move your slide in sideways if you do not see anything in the field of view When your specimen is well focused you may switch to higher magnification NEVER use the coarse focus knob at 10X or 40X! 10.09 5A-3 Heterotrophic Protists – Protozoa There are three categories of heterotrophic protists based on their mode of locomotion. Some organisms use extensions of their cell membrane and cytoplasm called pseudopodia. These pseudopods (“false-feet”) are used in locomotion in Amoeboids; they also surround food and form a food vacuole. Other protozoa use thin, long whip-like organelles called flagella. Flagella are used for locomotion in Flagellates, Euglenoids, Dinoflagellates, and some green algae. The number of flagella may be one, two, or many. Still other protozoa use short, cylindrical organelles called cilia. Cilia, although shorter and more numerous, are similar in construction to flagella. Paramecium is an example of a Protist that uses cilia for locomotion. Observation 1: Phylum Ciliates – Paramecium There are many, unicellular ciliates living in freshwater environments. These heterotrophs can be very small and tend to move very rapidly by means of cilia that cover the surface of the cell. A. Make a wet-mount of a flat slide from the culture on the side bench. The Paramecium looks like dust specks to the naked eye. Add a drop of methyl cellulose to slow down the microorganism. B. Observe under the compound microscope. Draw a picture of a Paramecium indicating the relative size you see in the circle below. You may be able to observe the formation of food vacuoles as the Paramecium consumes the yeast. In addition you may observe the action of the contractile vacuole which is involved in osmotic regulation. Kingdom: _______________ Phylum: ________________ Objective Lens: __________ Total Magnification: ______ 10.09 5A-4 1. What type of structure does Paramecium use for movement? 2. Is Paramecium autotrophic or heterotrophic? 3. Describe how Paramecium obtains nutrients. 4. What is the name of the channel through which the food enters this organism? 5. What is the natural habitat of Paramecium? C. Label the cilia, plasma membrane, oral groove, food vacuoles and the contractile vacuole on the Paramecium drawing. (Use your textbook or previous lab activities if you need help.) Paramecium Observation 2: Phylum Amoeboids – Amoeba 10.09 5A-5 Amoeba belongs to a diverse group of Amoeboids that use pseudopods for locomotion and/or feeding. Most are harmless heterotrophs that engulf food particles by phagocytosis, one type is a parasite that causes amoebic dysentery if swallowed. Amoeba are a freshwater amoeboid, other Amoeboids (Radiolarians and Foraminiferans) may live in marine habitats. C. Observe the culture dish of Amoeba on the side bench. The Amoeba will appear to be little white specks on the bottom of the jar. D. Using a deep-well slide make a wet-mount from the culture (be sure to completely fill the depression in the slide with liquid). Cover with a coverslip. E. Observe the Amoeba using the compound microscope. 1. Describe the body shape. 2. What structure(s) does an Amoeba use for movement? 3. Are Amoeba autotrophic or heterotrophic? 4. How does an Amoeba ingest its food? 5. What is the natural habitat of an Amoeba? F. The