The World of Microbes

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$Discrete Math Chapter 14 Descriptive Statistics 14.2 Exercise 1 ...$

The World of Microbes • Activity 45READINGClassifying OrganismsUntil recently, scientists classified organisms into five groups, calledKingdoms, as shown in Figure 1. New evidence has led to several alternativesto the five-kingdom system. Classification is a way to makesense of a lot of information. As the information changes, new classificationsystems evolve. For example, scientists have learned that bacteriacan be divided into two very different groups, called Bacteria andArchaea. Still, it is useful for you to think about five different groups oforganisms: animals, plants, fungi, protists, and bacteria.Figure 1: The Five-Kingdom Classification SchemeAnimals Plants Fungi Protists BacteriaYou are most familiar with animals and plants. They make up twokingdoms. A third kingdom is made up of fungi. The fungi includeyeasts (like the one you used in Activity 39, “Cells Alive!”), molds, andmushrooms. Protists and bacteria, like the ones you observed in Activity43, “Microbes Under View,” belong to two more groups of organisms.Notice that viruses are not included in the figure because theyare not considered to be living organisms.STOPPING TO THINK 1Think about all of the slides you have observed. Have youobserved cells of organisms from every kingdom? List all the cellsyou have observed from organisms in each kingdom.➢© 2006 The Regents of The University of California.Created by SEPUP, Lawrence Hall of Science, Berkeley, California. Adapted with permission. All rights reserved.C-71
Activity 45 • The World of MicrobesProtistsProtists are single-celled microbes that have a nucleus. While someprotists cause illness, many others are harmless. The Trypanosoma thatyou observed in Activity 43 is closely related to another type of Trypanosomathat causes sleeping sickness in people. Species of Parameciumare often harmless, living in fresh and salt water, where they feedon bacteria, algae, and other protists. Many types of Amoeba areharmless, while others cause illnesses of the digestive system.BacteriaBacteria are single-celled microbes that do not have a nucleus. Bacteriaare also the most common microbes and can be found everywhere—insnow, deserts, lakes, the ocean, and the human body. Asyou may recall, bacteria are extremely tiny; a thousand bacteriacould fit in a cluster on the dot of an “i.” There are more bacterial cellsin your digestive system and on your skin than the number of cellsthat make up your entire body!While some bacteria, such as Mycobacterium tuberculosis, cause diseases,other species of bacteria are helpful. In fact, without bacteria,nothing would ever decompose; the world would be full of deadorganisms, from the tiniest microbes to large plants and animals! Bacteriaalso are important in the preparation of foods and beverages.You may have noticed a statement on some yogurt containers: “containslive and active yogurt cultures.” That’s because yogurt is producedby the fermentation of milk by bacteria! Figure 2 shows theshapes and some information about different kinds of bacteria.STOPPING TO THINK 2Would you describe bacteria as being helpful or harmful to people?Explain.C-72© 2006 The Regents of The University of California.Created by SEPUP, Lawrence Hall of Science, Berkeley, California. Adapted with permission. All rights reserved.
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The World of Microbes

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