{"id":241,"date":"2015-07-14T16:27:49","date_gmt":"2015-07-14T16:27:49","guid":{"rendered":"https:\/\/courses.candelalearning.com\/biolabsxmaster\/?post_type=chapter&p=241"},"modified":"2017-11-01T15:39:31","modified_gmt":"2017-11-01T15:39:31","slug":"classification-and-tree-thinking","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/biolabs1\/chapter\/classification-and-tree-thinking\/","title":{"raw":"Classification and Tree Thinking","rendered":"Classification and Tree Thinking"},"content":{"raw":"Humans are excellent classifiers. Scientists classify organisms based upon features that are shared in common\u00a0with other related organisms. The formal process of classifying organisms is referred to as taxonomy.\r\n\r\nTraditional taxonomy relies primarily on physical traits, so that organisms that look alike are placed in the same\u00a0group.\r\n\r\nOne traditional taxonomic system, called the Linnaean system of taxonomy, established the following\u00a0categories:\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
<\/th>\r\nCritter 1<\/th>\r\nCritter 2<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
Domain<\/th>\r\nEukarya<\/td>\r\nEukarya<\/td>\r\n<\/tr>\r\n
Kingdom<\/th>\r\nAnimalia<\/td>\r\nAnimalia<\/td>\r\n<\/tr>\r\n
Phylum (Division)<\/th>\r\nChordata<\/td>\r\nArthropoda<\/td>\r\n<\/tr>\r\n
Class<\/th>\r\nMammalia<\/td>\r\nInsecta<\/td>\r\n<\/tr>\r\n
Order<\/th>\r\nCarnivora<\/td>\r\nHymenoptera<\/td>\r\n<\/tr>\r\n
Family<\/th>\r\nFelidae<\/td>\r\nFormicidiae<\/td>\r\n<\/tr>\r\n
Genus<\/th>\r\nFelis<\/td>\r\nSolenopsis<\/td>\r\n<\/tr>\r\n
Specific Epithet<\/th>\r\ndomestica<\/td>\r\ninvicta<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n
\r\n

Lab Question<\/h3>\r\n
    \r\n \t
  1. Can you tell what organisms are categorized here?<\/li>\r\n<\/ol>\r\n<\/div>\r\nClassifying organisms based on shared evolutionary history attaches powerful information to a classification\u00a0scheme. While traditional taxonomy relied primarily on classifying organisms by their shared physical characteristics (or morphology), technological advancements have allowed scientists to determine an organism's\u00a0evolutionary history more accurately. Taxonomy based on presumed evolutionary relationships is referred to as\u00a0phylogeny.\r\n\r\nUsually, traditional taxonomic systems agree with phylogenetic systems when determining where organisms\u00a0should be classified. However, sometimes, striking conflicts can arise. For example, birds are traditionally\u00a0placed in their own class Aves<\/em>. However, a wealth of research indicates that birds are actually living\u00a0dinosaurs, and are thus technically reptiles.\r\n\r\nCheck out some\u00a0more information on this fascinating situation<\/a>.\r\n

    Part 1: Dichotomous Keys<\/h2>\r\nA dichotomous key<\/strong> is an identification key that consists of a series of choices that ultimately lead to the\u00a0identification of the object in question. In each step of a dichotomous key, the user has two choices and must\u00a0pick the one that most correctly describes the object. Each choice leads to a new set of choices. To help you\u00a0understand how a key like this works, consider the following four insects:\r\n\r\n\"Illustrations\r\n\r\nAfter studying the insects, you might classify the insects by wing covering, body shape, and the direction in\u00a0which the wings point.\r\n\r\nTo begin the key, you could start separating the four insects based on wing covering\u2014\"wings covered by\u00a0exoskeleton\" vs. \"wings not covered by exoskeleton.\"\r\n\r\nThe first step in the key could be organized the following way: <\/strong>\r\n
      \r\n \t
    1. wings covered by an exoskeleton. . . . . . . . . . . . . .\u00a0go to step 2<\/strong><\/li>\r\n \t
    2. wings not covered by an exoskeleton . . . . . . . . . .\u00a0go to step 3<\/strong><\/li>\r\n<\/ol>\r\nStep 2 consists of a pair of statements that distinguishes between the ladybug and the grasshopper.<\/strong>\r\n
        \r\n \t
      1. body has a round shape . . . . . . . . . . . . . . . . . . . . . ladybug<\/strong><\/li>\r\n \t
      2. body has an elongated shape. . . . . . . . . . . . . . . . .\u00a0grasshopper<\/strong><\/li>\r\n<\/ol>\r\nStep 3 consists of a pair of statements that distinguishes between the dragonfly and the housefly.<\/strong>\r\n
          \r\n \t
        1. wings point out from the side of the body . . . . . .\u00a0dragonfly<\/strong><\/li>\r\n \t
        2. wings point to the posterior of the body. . . . . . . . housefly<\/strong><\/li>\r\n<\/ol>\r\nNotice that there were four organisms to be identified and it only took three steps to identify them. After making\u00a0a key, you should end up with one less step than the total number of organisms you are trying to identify.\r\n\r\nWhen constructing a key, keep the following in mind: <\/strong>\r\n