Protists - Biology 05B Spring Quarter 2006 - page 1 The...

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Biology 05B – Spring Quarter 2006 - page 1 The Protists The term protist refers to an organism belonging to an alliance of organisms that are diverse in form, life style, and ancestry. The primary feature that distinguishes protists from other eukaryotic organisms is that most of its members are unicellular. As mentioned in the introduction, the focus of study in Biology 5B is introduce students to the diversity of organisms and the different ways that organisms confront some of the basic physiological challenges of life. While the protists may not be the best organisms to use for introducing some of the basic concepts of organismal diversity (the relationships among these organisms are very complicated and occurred over a very long time span), they do provide many excellent examples how organisms fulfill some of the basic requirements of life. Their suitability for this lies in their unicellular organization. As unicells they are very accessible for use in the teaching lab, and easy to observe and study in their entirety than are multicellular organisms. All organisms share many common needs. Among these are the need to acquire nutrients from the environment, distribute these nutrients to all parts of the body, exchange gasses (0 2 and C0 2 ) with the environment, eliminate metabolic wastes, and reproduce. Many organisms must also be able to move about their environment. Most maintain the form or shape characteristic of their species. Protists perform all, or most of these requirements in the context of a single cell. Before going on with brief discussions of how each of these requirements are met by protists, it must be mentioned that most of the principles to be described also apply to the cells of multicellular organisms. Given this fact, you should see that your efforts in this lab are also relevant to more complex organisms including yourself. Nutrition. Protists are either autotrophic or heterotrophic. Autotrophic protists, collectively referred to as algae, make their own food by photosynthesis. Their primary photosynthetic pigment is chlorophyll A, but also utilize a wide array of other pigments in light capture. They are often green, but may vary in color because of the presence of these other pigments. In fact, the classification of algae is based in part upon the combination of photosynthetic pigments present and upon the chemical composition of their stored photosynthate (e.g. the green algae use chlorophyll A and B, yellow pigments called carotenoids, and store starch). It should be mentioned that some heterotrophic protists acquire an autotrophic capacity by incorporating algal endosymbionts into their cells. Heterotrophic protists may be either saprozoic, that is they absorb complex dissolved nutrients from their environment, or holozoic. Holozoic forms ingest solid food from their environment which must be broken down by a process of enzymatic digestion before it can be utilized. The presence of specialized structures , e.g., tentacles and cytostome, for the capture and ingestion of food is often
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This note was uploaded on 04/17/2008 for the course BIO 005b taught by Professor Chappel during the Spring '07 term at UC Riverside.

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Protists - Biology 05B Spring Quarter 2006 - page 1 The...

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