CHAPTER I (106) - CHAPTER I CLASSIFICATION: TAXONOMY On a...

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CHAPTER I CLASSIFICATION: TAXONOMY On a fundamental level, there are only two classes’ objects on our planet. One class consists of objects whose structure and behavior are essentially inert – they obey physical forces in a purely mechanical way. These objects are the H 2 O of the oceans, the rocks of the mountain ranges, the sands of the deserts, briefly NON-LIVING OBJECTS. In contrast, the objects in the second class come in a rich and practically infinite variety. This class consists of LIVING OBJECTS, which we call ORGANISMS . One of the most striking characteristics of organisms – and one that clearly separates them from inert objects – is that they REPRODUCE; that is they produce new organisms. In fact, they produce organisms more or less like themselves, which means that organisms must have HEREDITY, a set of instructions that specifies the properties of their descendants. According to the fossil records, the most primitive organisms known, - the bacteria and cyanobacteria- dates back to over 3 Billion Years Before Present (BP), first land plants and insects over 400 Million Years BP, and the first birds and the mammals over 180 Million Years BP.
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Since the simplest forms of life arose, innumerable different kinds of organisms, increasingly complex, adapted to widely varying environments through a process called EVOLUTION. As the time passed, a system is required to establish an order to classify these organisms. Although many such systems were established, the one which uses the evolutionary relationships betweens organisms – the commonality of ancestry- find increasingly more support from the scientific circles. The TAXONOMIC system that we will be following recognizes 5 broad categories, or KINGDOMS ( see CHAPTERI.PPT file: Slide 2 ) which are: 1) MONERA 2) PROTISTA 3) FUNGI 4) PLANTAE 5) ANIMALIA 1) MONERA KINGDOM Members of the Monera differ from those of the 4 other kingdoms in that their cells lack a membrane-enclosed nucleus, as well as other intracellular membranous structures present in the cells of other types of organisms. Therefore they are PROKARYOTIC organisms ( Slide 3 ). This kingdom has two broad subgroups:
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a) Bacteria b) Cyanobacteria a) Bacteria The most abundant organisms in the world, bacteria, are single-celled (unicellular) and can be seen only under magnification. Most bacteria can not manufacture their own food from simple inorganic substances and must instead obtain their nutrients, already synthesized from other organisms. Some obtain these nutrients from dead organisms (decomposer bacteria); other from living organisms (pathogenic bacteria). Most bacteria have strong cell walls ( Slide 3 ) which protect them from damage as well as other structures present ( e.g . flagellum and pillus for locomotion ( Slides 4-5 ) make them to survive in many diverse habitats ranging from hot springs to glaciers in Antarctica. Though some bacteria are disease-producing agents (pathogenic) that attack
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This note was uploaded on 04/03/2010 for the course BIO 210 taught by Professor Onde during the Spring '10 term at Middle East Technical University.

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CHAPTER I (106) - CHAPTER I CLASSIFICATION: TAXONOMY On a...

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