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 Prokaryotic Prokaryotic Eukaryotic Eukaryotic Eukaryotic Eukaryotic
Domain Archaea Bacteria Eukarya Eukarya Eukarya Eukarya
Kingdom Example Not Used Prokaryotic organisms found in extreme environments Not Used common bacteria, cyanobacteria Protists algae, Paramecium, Amoeba, Euglena Fungi mushrooms, mold, Penicillium Animals vertebrates, insects, nematodes, sponges 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.
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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.
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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!
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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: ______
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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
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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 circle below represents what you would see through the microscope. Draw a picture of an Amoeba indicating the relative size you see in the circle. Label the plasma membrane, cytoplasm, and a pseudopod. (Use your textbook or the boards if you need help.)
Phylum: ________________ Objective Lens: __________ Total Magnification: ______
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Observation 3: Phylum Euglenoids – Euglena Euglena are a single-celled protist that moves by means of flagella and is found in nutrient-rich (polluted) water. Containing chloroplasts, Euglena are able to use chlorophyll to photosynthesize in the light, but they can also absorb nutrients. They lack a cell wall and are surrounded by a flexible pellicle that protects them while allowing for flexibility. A. Make a wet-mount on a flat slide from the culture on the side bench. Cover with a coverslip. B. Observe the Euglena using your compound microscope at 4X, 10X and then 40X. 1. What type of structure does Euglena use for movement? 2. Is Euglena autotrophic or heterotrophic? 3. What pigment is involved in photosynthesis? 4. What is an alternative feeding strategy that Euglena can use in the absence of light? 5. What is the natural habitat of Euglena? C. Label the flagellum, plasma membrane, and chloroplasts in the Euglena drawing. (Use your textbook or the boards if you need help.)
Euglena D. Draw a picture of Euglena indicating the relative size you see in the circle below.
Phylum: ________________ Objective Lens: __________ Total Magnification: ______
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Autotrophic Protists - Algae There are many different types of algae that differ according to their body form, the type of photosynthetic pigments they use and variations in their flagella. There are several possible forms, these include unicellular, colonial and filamentous organisms. Unicellular algae only have one cell. Colonial algae are temporary clusters of cells that can be organized, but each cell is an individual organism that can break off and survive on its own. Filamentous algae have many interconnected cells that form a long line of cells – a filament; these are a true multicellular form. There are also some multicellular algae that form highly branched structures, others form flattened sheets. In multicellular alga the tissues are simple and do not show much (if any) specialization. Observation 4: Phylum Dinoflagellates – Ceratium (Optional –determined by instructor) Dinoflagellates are bi-flagellated, single-celled plankton in freshwater and marine habitats. They contain chlorophyll (the primary photosynthetic pigment) and a yellow-brown accessory pigment (fucoxanthin). Periodically dinoflagellates become extremely numerous and create “algal blooms” known as red tides. During red tides toxins produced by dinoflagellates accumulate in shellfish and cause them to be quarantined. Dinoflagellates also can be bioluminescent (give off light); when this occurs the waves and disturbed sand give off a greenish glow. A. Obtain a prepared slide of Ceratium and examine it under the compound microscope with the 4X, 10X, and then 40X lens. 1. What type of structure does Ceratium use for movement? 2. Is Ceratium autotrophic or heterotrophic? 3. What is the cell wall made of? B. Label the cell wall and flagella in the Ceratium drawing. 4. What is the ecological importance of dinoflagellates in freshwater and marine environments? 5. What is a red tide? What is its significance?
6. What is bioluminescence?
7. To what phylum does Ceratium belong? Observation 5: Phylum Diatoms Diatoms are single-celled, photosynthetic marine and freshwater plankton. Like all photosynthetic organisms they use chlorophyll to capture sunlight but they also have the yellow-brown accessory
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pigment (fucoxanthin) that aids photosynthesis and gives them their golden color. Most are nonmotile, but a few are able to glide along surfaces. A. Obtain a prepared slide of diatoms and examine it under the compound microscope with the 4X, 10X, and then 40X lens. 1. Describe the cell wall of diatoms. What is the cell wall made of? What makes it unique? 2. What pigments are present in diatoms? B. Draw at least 2 diatoms with different shapes from the prepared slide. You may make a wet mount if material is available.
Phylum: ____________________ Objective Lens: ______________ Total Magnification: __________
3. In what natural habitat(s) are diatoms found? 4. Are diatoms autotrophic or heterotrophic? 5. In what two ways are diatoms ecologically important?
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Observation 6: Phylum Green Algae – Spirogyra Green algae are found in most habitats. Members range from unicellular, to colonial, to filamentous, to blade-like. All contain the green pigment chlorophyll that is primarily responsible for photosynthesis. The colonial Volvox and filamentous Spirogyra are both found in fresh water; the blade-like forms, such as Ulva, are marine species. A. Make a wet-mount of Spirogyra on a flat slide from the culture on the side bench. Cover with a coverslip. B. Observe using the compound microscope. C. Label the cell wall, chloroplast, and cytoplasm on the Spirogyra drawing.
Spirogyra 1. What type of form does Spirogyra have (filamentous or colonial)? 2. Is Spirogyra autotrophic or heterotrophic? 3. What primary pigment is involved in photosynthesis? Describe the shape of the chloroplast. 4. What is the cell wall made of? 5. Is Spirogyra motile? 6. To what phylum does Spirogyra belong? 7. What is the natural habitat of, and what is the ecological importance of Spirogyra and other filamentous alga?
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Observation 7: Phylum Green Algae – Volvox (review) A. Label the drawing of Volvox. Identify the colony, the individual cells, and daughter colonies.
Volvox
1. How does this colony move?
2. To what phylum does Volvox belong? 3. How does Volvox obtain it’s nutrition? 4. What pigment is involved in photosynthesis? 5. What is the natural habitat of Volvox?
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Observation 8 – Marine Macro-algae There are three phyla of marine macro-algae: Green Algae, Brown Algae (Seaweed or kelp), and Red Algae A. Observe the fresh and/or preserved specimens on display. B. Be able to distinguish between the phyla of algae on display. 1.
Macro-algae are key producers in which aquatic ecosystem?
2.
What pigment is responsible for the green pigment in algae and plants? Phylum Green Algae 3. List an example of a green macro-alga (on display). 4. What is the cell wall made of?
Phylum Red Algae Specialization 5. List two examples of red algae on display. a. b. 6. What is the advantage of the red pigment found in red algae?
7. What substance deposited in the cell wall makes coralline red algae hard? Phylum Brown Algae Specialization 8. List two examples of brown algae on display. a. b. 9. List the two pigments found in brown algae. a. b. 10. What is the cell wall made of?
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Macro-Algae (Protist Kingdom) and Land Plants (Plant Kingdom) 11. Which algae are the closest relatives of land plants? Why ?
12. Draw and label a brown alga with a blade, bladder, stipe, and holdfast.
13. How does this body plan compare to that of a typical flowering plant?
14. Similar structures found in genetically unrelated organisms are often attributed to their adaptations to similar environments or similar way of life (ecological niche). When two different lineages face similar environments, constraints, or problems, natural selection may act on both lineages in the same way. This process can cause both lineages to evolve similar traits or structures. This is called "convergent evolution." What specific environmental factors and/or “way of life” may have selected for the similar body plans of kelp in the sea and plants on land?
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Phylum
Example(s)
Autotroph or Heterotroph
Cilates
Amoeboids
Euglenoids
Dinoflagellates
Diatoms Green Algae
Red Algae
Brown Algae
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Means of Locomotion
Pigments (if any)
Habitat
Special Characteristics
