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Plantlike Protists: Unicellular AlgaeCLASSIFICATION Taxonomy, or the science of classifying organisms, groups organisms into categories based on various characteristics. Aristotle Aristotle’s classification system proposed that if something moves, it is an animal, and if it doesn’t, it is a plant. Of course, sponges were mistakenly taken for plants, and when they threatened the shellfish industry centuries ago, were “killed” by being cut up and tossed back into the sea. To the surprise of the shellfish harvesters, the next year, the number of sponges had increased; the shellfishers were actually helping the sponges reproduce (asexually) by their actions. Linnaeus Linnaeus proposed naming organisms by a two-name system that we call binomial nomenclature. These were very specific names based on the organism’s characteristics and are the genus and species of today. Note that the genus is always capitalized and the species is not, as in Terrestris americanus, and the entire name is underlined or italicized. Modern The modern system of classification now contains five major groups called kingdoms. Life on the planet could be seen as analogous to a grocery store. The major consumer item areas, such as produce, dairy, and canned goods, would be analogous to the kingdoms of living things. As with the grocery store, the sub-categories get more and more specific until it is possible to name an item exclusive of all other items in the store. You should know the categories, starting with the largest (the kingdom) and continuing to narrower and narrower groups in the sequence: Kingdom, Phylum, Class, Order, Family, Genus, and Species. In plants, the word “phylum” is replaced with the word “division.” Modern day study has become so detailed that we will now find such categories as sub-genus and super-species. The student is responsible only for the above schema. Most beginning biology students become familiar with the mnemonic—memory device—in a variety of expressions, one being King Phillip Come Out For Goodness Sakes. The first letter of each word, in the order given, is the first letter of each of the major categories in taxonomy.
EXAMPLES OF GENUS AND SPECIES Canis familiarus domesticated dog Felis feline domesticated cats Homo sapiens modern humans
Kingdom Monera Prokaryotes are single-celled, microscopic prokaryotic cells with no distinct nucleus or other membrane-enclosed organelles. Bacteria Bacteria have cell walls composed of peptidoglycan, an amino acid–sugar complex, and circular DNA. Composition of the cell wall provides us with the Gram staining means of identifying certain types of bacteria. Reproduction of bacteria was outlined in an earlier chapter. Some bacteria possess flagella. While many bacteria are decomposers, some fix nitrogen and other elements in a form usable by organisms, and some are pathogenic. A. Shapes Bacteria can be found in three shapes: coccus (round-shaped), bacillus (rod-shaped)—the one the SAT II Biology exam commonly refers to when asking a question about bacteria—and spirillus (spiral-shaped).
B. Types Aerobic (oxygen-needing) bacteria are the largest group of bacteria. Anaerobic (not needing oxygen) bacteria are found in two groups: those that need an oxygen-free environment (obligate) and those that do not need a lack of oxygen, but a small amount of oxygen will not kill them (facultative).
Kingdom Protista Protists belong to the Kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms. Characteristics of Protists
Protista = the very first Classification of Protists
Animallike Protists - also called protozoa (means "first animal") - heterotrophs .Animallike Protists: Protozoans Four Phyla of Animallike Protists
Zooflagellates move using one or two flagella
Sarcodines Ameba moves using pseudopodia ( "false feet" ), which are like extensions of the cytoplasm --ameboid movement
Ciliates Paramecium move using cilia
Sporozoans do not move on their own Plantlike Protists: Unicellular Algae
Euglenophytes Euglena live in water
Ecology of Unicellular Algae
Date: 2016-01-03; view: 3498
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