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Diversity of Life Taxonomy All known life forms are systematically arranged and placed in various groups. This process is called taxonomy. The following example illustrates why this is important for communication among biologists. Europeans call the European house sparrow, now common in the United States, many different names: England Germany Denmark Norway House sparrow Haussperling Graaspurv Graaspurv France Italy Spain Holland Moineau domistique Passera oltramontana Gorrion Musch It is clear that the above can lead to confusion when scientists of different countries are trying to communicate with each other. Another example is the burrowing rodent called a gopher found throughout the western United States. In the southeastern United States the term gopher refers to a burrowing turtle very similar to the desert tortoise found in the American southwest. One final example; two North American mammals known as the elk and the caribou are known in Europe as the reindeer and the elk. We never sing “Rudolph the Red-nosed elk”! Confused? This was the reason for creating an internationally recognized system of naming organisms. To avoid confusion, living organisms are assigned a scientific name based on Latin or Latinized words. The English sparrow is Passer domesticus or Passer domesticus (italics or underlining these two names is the official written representation of a scientific name). Using a uniform naming system allows scientists from all over the world to recognize exactly which life form a scientist is referring to. The naming process is called the binomial system of nomenclature. Passer is comparable to a surname and is called the genus, while domesticus is the specific or species name (like your given name) of the English sparrow. Now scientists can give all sparrow-like birds the genus Passer but the species name will vary. All similar genera (plural for genus) can be grouped into another, “higher” category (see below). Study the following for a more through understanding of taxonomy. Taxonomy Analogy Kingdom: Animalia Country Phylum: Chordata State Class: Aves City Order: Passeriformes Street Family: Ploceidae Genus: Passer Species: domesticus House number Surname Given name Today there are over 1 million known and named species of animals. The majority of scientists believe that there are 10 to 50 million additional species not yet described and named. In Zoology 5 we will confine our study to the most common animal phyla. In addition to eliminating confusion, taxonomy allows us to identify most kinds of animals without ever seeing them before or without knowing their names using a dichotomous key. Given an animal, the key presents a pair of statements (occasionally 3). We select the statement that best describes the animal under question. At the end of the statement is a number directing the key’s user to proceed to the next pair of statements. Continue this process until a taxon (phylum, class, etc.) rather than a number appears at the end of a statement. If done correctly you will have discovered the correct taxon for the animal in question. Most of us know what a lobster looks like (see drawing at right). Look at statements 1 and 1’ on the key. 1’ is correct and directs us to go to 2. The lobster is bilaterally symmetrical, hence 2’ directs us to go to 16. The lobster lacks 8 calcareous plates so 16’ directs us to 17. The lobster is not worm-like, so we go to 20. There is an external skeleton thus the lobster is in the Phylum Arthropoda as well as the fact that we should continue on to 21. Antennae are present Figure so we must go to 22. Since there are 2 pair of antennae, gills and 5 pairs of jointed appendages the lobster is in the class Crustacea. As you proceed record the number for each successive step so that you can go back if you made a mistake. For the above example the steps were 1’,2,’ 9,’ 16’, 17, 20, 21, 22. More complicated keys exist allowing a determination of genus and species, however we will not use them in this course. The exercise today will be two-fold. 1. Identification of specimens found in lab beginning with yourself. Record the numbered steps you followed for each specimen. List a few key characteristics and indicate the phylum and class (if given) of each animal keyed out. Your instructor will indicate how many animals to key in this exercise. 2. Go to the seawater tank and key out the animals present List the phyla and classes present. Morphological Terms Microscopic - Organisms whose gross structures can only be seen with the aid of a microscope or other magnifying instrument. Macroscopic Organisms whose gross structures can be seen with the unaided eye. Unicellular Organisms consisting of only a single cell. Multicellular Organisms composed of many cells. Many are microscopic. Asymmetry - Organisms that cannot be divided into identical halves. Radial symmetry - Organisms that are circular or cylindrical in form and can be divided into identical halves or mirror images in several different ways. Bilateral symmetry -Organisms that can cut along only one plane to achieve equal halves. Body Orientation - The portion of a bilaterally symmetrical animal that moves forward and contains the mouth is anterior. Opposite anterior is termed posterior. The upper surface or back is dorsal and the underside (or belly) is ventral. Structures toward the center are medial and those toward the sides are lateral. Example: Microscopic, unicellular animal, asymmetrical Figure Figure Figure Radial Bilateral Example: Macroscopic, multicellular animals, symmetry indicated (note orientations). Segmentation – Many animals have structures or body parts, which are linearly repeated analogous to the individual pieces in a loaf of sliced bread. The repeated units are called segments, somites or metameres. Segments may be external as well as internal. Internal segmentation may not be accompanied by external segmentation so one must exercise care when deciding if an animal is or is not segmented. Furthermore, serial repetition of structures found on individual appendages (i.e.suckers on the arms of an octopus) is not considered segmentation. Figure Example: Externally segmented animal Appendages - structures, or parts that extend out from the animal’s body and serve various functions such as (1) sensory antennae, (2) offense/defense, (3) locomotion, (4) sperm transfer in males, (5) aid in respiration and carrying eggs in females, (60 backward swimming, and (not shown) food handling, gills, etc. Figure Figure Example: Internally segmented animal with an exoskeleton. Example: External segmentation with an endoskeleton. Skeleton – a skeleton is the hardened framework of an animal’s body which serves in support, protection and muscle attachment. Some animals have external skeletons or exoskeletons while others have internal skeletons or endoskeletons.