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Protist Diversity

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Protist Diversity Biological Principles II Name _______________________________________ Protist Diversity INTRODUCTION e term “protist” refers to a hodgepodge of organisms ranging from unicellular heterotrophs to very large multicellular autotrophs. ey include algae (plant-like organisms which photosynthesize using different pigments), protozoans (animal-like organisms which consume other organisms and use different methods of movement), and members that are fungal-like and feed through absorption. Over the course of the next two labs, we will be examining many members of this paraphyletic group. SUPERGROUP EXCAVATA: e excavates are a group of unicellular organisms that have modified mitochondria which undergo anaerobic respiration. Most have a body groove that may act as a point of anchorage for their flagella. Examples include Giardia lambia, a human intestinal parasite transmitted by contaminated drinking water; Trichonympha sp., a mutualistic symbiont living in the gut of termites that aids in the digestion of wood; Euglena sp., a photosynthetic flagellate common in pond water; and Trypanosoma sp., a human blood parasite that causes African sleeping sickness. Procedure: 1. Obtain a prepared slide of Giardia lambia. Look at it first with the 10x objective, to find a specimen and then study it through your 40x objective. Giardia is an intestinal parasite of vertebrates. It has a feeding stage called a trophozoite in its life cycle and a cyst stage. What you are looking at is the trophozoite. Draw an example of a trophozoite in the space provided below. In your drawing, label the two nuclei (that look like eyes) and the flagella (it has four). Fig. 1. Giardia lambia. 2. Make a wet mount of Euglena and observe through your compound microscope. Reducing the light intensity will help you see structures in the organism. As you study the Euglena, find the following structures: flagellum, stigma (red eyespot), chloroplast, and pellicle (flexible outer covering). Draw an example of Euglena below and label the structures listed above. Fig. 2. Euglena. Question 1: Does the flagellum push or pull the organism through the water? Question 2: What evidence is there that the pellicle is flexible? 3. Observe the demonstration slide of Trypanosoma sp. is organism is a well-known parasite of vertebrates. (It is seen here in a field of red blood cells). T. brucei causes African sleeping sickness, while T. cruzi causes Chaga’s disease in Central and South America. 2 SUPERGROUP CHROMALVEOLATA: e chromalveolates are an even more diverse and controversial group of protists than the Excavata, with at least six major groups of organisms. e first type of chromalveolate are the alveolates, characterized by membrane-lined sacs called alveoli that regulate the diffusion of materials across the plasma membrane. Alveolates are further divided into three sub-groups: dinoflagellates, ciliates and apicomplexans. Procedure: 1. Make a wet mount of the dinoflagellate Amphidinium. Look at it first with the 10x objective to find a specimen, and then study it through your 40x objective. Dinoflagellates, along with diatoms, make up most of the phytoplankton found in marine and freshwater ecosystems. As you observe this dinoflagellate, focus up and down. You should notice two things: dinoflagellates have two flagella – one in a groove wrapping around the cell, and one in a longitudinal groove extending from the end of the cell. You should also note that the cell is covered in plates of cellulose, referred to as a theca. Draw an example of a dinoflagellate below. In your drawing, note the two flagella and the theca. Fig. 3. Amphidinium. Ciliates are a type of alveolate that move using cilia. ey have rows of these hair-like projections covering one end or sometimes their entire cell. Cilia both aids in movement and in capturing food. 2. Create a wet mount with a drop of water containing the ciliate Paramecium. You will need to add a drop of Protoslo to the drop of water before you place the coverslip on it. Look at it first with the 10x objective to find a specimen, and then study it through your 40x objective. Once you find a specimen, observe the activity of that cell for a few minutes. Draw the cell you have observed in the space on the following page. Label the cilia. 3 Fig. 4. Paramecium Stramenopiles are the second sub-group of chromalveolates. is group is characterized by having flagella with hair-like projections along the length of the shaft. Diatoms serve as prime examples of stramenopiles, physically encased by silica. is rigid encasement increases the tensile strength of these organisms, especially when moving towards deeper parts of the ocean where pressure significantly increases. e silica casing contains holes where materials and water pass through. In addition to the diatoms, Phaeophyta, the brown algae, and Oomycetes, the water molds, also belong to this group. We will examine examples of Phaeophyta next week in lab. 3. Observe the demonstration slide of mixed diatoms. Note the distinct cell wall that appears like a glass shell. Draw some of the cells you see below. Fig. 5. Diatoms. 4 SUPERGROUP RHIZARIA: e supergroup Rhizaria consists of a wide variety of protists that have been grouped together based on DNA sequence similarities. is group has thin cellular extensions called pseudopodia that assist in locomotion. e rhizaria consists of three major groups, based on their skeletal features: Radiolaria, Foraminifera and Cercozoa. Procedure: 1. Create a wet mount with a drop of water containing the radiolarian Actinosphaerium. Look at it first with the 10x objective to find a specimen, and then study it through your 40x objective. Radiolarians have an endoskeleton composed of silicon dioxide, causing Actinosphaerium to have a sun-like appearance. Draw some of the cells you see below. Fig. 6. Actinosphaerium. 2. Observe the demonstration slide of foraminiferans (forams). Unlike the radiolarians, the foraminiferans have an outer shell of calcium carbonate. Draw some of the cells you see below. Fig. 7. Foraminifera. 5 SUPERGROUP ARCHAEPLASTIDA: e supergroup Archaeplastida includes plants and protists capable of conducting photosynthesis, based on the presence of chloroplasts. Archaeplastids encompasses three major groups, based on the type of pigment present within its cells: the Rhodophyta (red algae), the Chlorophyta (green algae), the Charophyta (another type of green algae), and the land plants. Procedure: 1. Visit the Archaeplastida table and view some of the examples shown there. We will be examining these groups during later labs. SUPERGROUP UNIKONTA: e unikonts consist of a wide spectrum of eukaryotic organisms, ranging from the amoebas to the animals. Phylogenetic analysis established two major unikont clades, namely the amoebozoans and the opisthokonts, the collective assembly of protists, fungi and animals. e amoebozoans are unicellular and have pseudopodia which are movable extensions of cytoplasm used for locomotion and gathering food. e amoebozoans include the amoebae, the cellular slime molds, and the plasmodial slime molds. Procedure: 1. Visit the Unikonta table and view some of the examples shown there. On the laptop, you can view a YouTube clip of slime molds. 2. Create a wet mount with a drop of water containing the amoebozoan Amoeba. Look at it first with the 10x objective to find a specimen, and then study it through your 40x objective. Observe the activity of that cell for a few minutes. Notice that the cytoplasm is divided into two distinctive parts. e ectoplasm is a thin, clear, non-granular region of cytoplasm directly beneath the plasma membrane. e endoplasm is a granular region of cytoplasm that makes up most of the amoeba. You may also notice food vacuoles created through phagocytosis. Draw the specimen you see below. Label a pseudopod, the ectoplasm, endoplasm, and a food vacuole. Fig. 9. Amoeba sp. 6 Examples: Giardia lambia Euglena sp. Trypanosoma sp. Amphidinium sp. Paramecium caudatum Mixed diatoms (Photograph) (Photograph) (Photograph) Foraminifera Actinosphaerium (Photograph) Spirogyra Charales Geranium (Photograph) Amoeba sp. Bracket fungus Frog, Clam 7.
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