Using Dichotomous Key to Identify Sharks
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Also, the may have been transported, particularly to locations near ports and airports, or it may have changed its range e. It is not based on the classification of the included species — compare with the.
Shark Dichotomous Key 1 A Body kite like in shape if viewed from above Go to statement 12 B Body not kite like in shape if viewed from above Go to statement 2 2 A Pelvic fin absent and nose sawlike Family B Pelvic fin present Go to statement 3 3 A Six gill slits present Family B Five gills present Go to statement 4 4 A Only one dorsal fin present Family B Two dorsal fins present Go to statement 5 5 A Mouth at the front of the head rather than back along underside of head Family B Mouth back along underside of head Go to statement 6 6 A Head expanded on the side with eyes at the end of expansion Family B Head not expanded Go to statement 7 7 A Top half of caudal fin exactly same size and shape as bottom half Family Isuridae B Top half of caudal different in size and shape from the bottom half Go to statement 8 8 A First dorsal fin very long, almost half the length of the total body Family B First dorsal fin length much less than the half the total length of body Go to statement 9 9 A A. Students must always start and read and choose between the first set of paired statements. Lobatae, : 5 2.
Using Dichotomous Key to Identify Sharks - What is a classification key and how is it used?
Bioterms Taxonomy is the classification of organisms, both plant and animal, based on their structural characteristics and evolutionary history. Aristotle is credited with creating the first classification system more than 2,000 years ago. He classified living things as plant or animal according to their appearance. This system was expanded later by the Romans to be more specific down to the individual organism types, such as a cow or elm tree. As more organisms were identified and classified, more words were needed to separate similar organisms, such as two types of dog. So new organisms were classified by using lengthy descriptors, which eventually became cumbersome to use as more organisms created the need for more words. Carolus Linnaeus, a Swedish naturalist, began the struggle to classify all living things by proposing a binomial, or two-name system. In this model, the genus is the first name, and the species is the second name, with the first letter of the genus name always capitalized. Therefore, each organism is sorted by a genus, species classification, such as Homo sapien for man. Linnaeus also proposed to expand the genus-species nomenclature to include larger units of likeness, for recognizing extended degrees of kinship. Today, the categories are still based on Linnaeus's work. For example, the taxonomy for humans is the following: Domain—Eukaryote Order—Primate Kingdom—Animal Family—Hominidae Phylum—Chordate Genus— Homo Subphyla—Vertebrate Species— Sapien Class—Mammal Moving from domain to species, the organisms are more closely related, such that organisms in the same species have a greater degree of kinship than organisms that are similar only at their family level. For instance, both cats and humans are in the class Mammalia, but their pathways separate at that point because cats are in the order Carnivora, whereas humans are Primates. However, a grizzly bear, a black bear, and a polar bear are more closely related because they are in the same family: Ursidae. Further, grizzly bears and black bears are more closely related to each other than to the polar bear because the grizzly and black bear are in the same genus: Ursus, but the polar bear is not. Systematics operates to identify relative kinship and evolutionary intersects among species. Examine the following classification chart. Which pair of organisms are most closely related? Organism 2 is a lion, organism 3 is a common housecat, and organism 1 is a human. Binomial Classification The binomial classification system proposed by Linnaeus allowed him and others to group organisms together based on common structures, functions, and resulting behaviors, which led to the science of taxonomy, or classification. Often biologists use a taxonomic key, also known as a dichotomous key, to identify unknown organisms by their physical characteristics. Taxonomic keys work on a base-two premise: The organism either has the characteristic or does not. The resulting answer then directs the biologist to the next set of questions until all the characteristics have been accounted for and the organism is identified. The following Binomial classification illustration is a fictitious key that demonstrates the process. It has two legs. It has more than two legs. Go to 2 2a. Go to 3 2b. It is not shaded. Go to 4 3a. It has a round head. It does not have a round head. Gorgot Backtracking from the dichotomous key, a dumlop is an organism that has more than two legs, is shaded, with a round head. Most dichotomous keys are quite lengthy, to account for all the features that a set of organisms may possess. The broadest keys begin at the kingdom level and proceed to the more specific genus and species levels. Excerpted from The Complete Idiot's Guide to Biology © 2004 by Glen E. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group USA Inc. To order this book direct from the publisher, visit the or call 1-800-253-6476. You can also purchase this book at and.
They must continue to refer to the same item or organism and follow the directed path until they come to a name for that organism. However, characters which are neither differential nor diagnostic may be included to increase comprehension especially characters that are common to the group, but not unique. As more organisms were identified and classified, more words were needed to separate similar organisms, such as two types of dog. The creature has an M shaped bottum. The creature has no mouth. Have them add the definition of dichotomous key to their vocabulary words. The creatrue has no antennae.
