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1.2: Taxonomy

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    Introduction: clipboard_eb698b448217d458fa6ac70352022a4ea.png

    Because the diversity of life on Earth is so vast, biologists use a general system of classification and naming organisms (taxonomy) to track and organize species based on evolutionary relatedness. The broadest taxon is the domain; organisms belong to one of the three domains (Bacteria, Archaea, and Eukarya). Within the domains are increasingly specific taxa, usually following the order in the table below.

    The scientific name of an organism is given using binomial nomenclature; the genus and species of an organism give its specific scientific name. These names are usually derived from Greek or Latin, and therefore must be italicized when written. The genus is to be capitalized and the species is lower case. For example, the scientific name of a common wombat (top) is Vombatus ursinus.

    Let us compare the wombat to a similar species, a quokka (bottom).

    Note that both animals differ only when we reach the family level. If you knew that a kangaroo was in the same family as a quokka, would you assume the quokka was more closely related to a kangaroo or a wombat?

    Scientific names might seem confusing, but are useful for several reasons. Common names tend to vary according to region (crawfish, crayfish, mudbug, crawdad), but the scientific name is always the same.

      Wombat Quokka
    Domain Eukarya Eukarya
    Kingdom Animalia Animalia
    Phylum Chordata Chordata
    Class Mammalia (Marsupialia) Mammalia (Marsupialia)
    Order Diprotodontia Diprotodontia
    Family Vombatidae Macropodidae
    Genus Vombatus Setonix
    Species ursinas brachyurus


    1. Llamas, alpacas, and camels are all in the same family: Camelidae. Therefore, it is reasonable to assume that these animals will also be in the same...

    2. The scientific name of the brown-throated three-toed sloth is named Bradypus variegatus. What is the genus of the organism? The species?

    Part 1: A Simple Dichotomous Key

    A dichotomous key is a tool used to determine the identity of species that have been previously described. You can think of it as a series of questions in which each question only has two possible answers.

    In the table below, you have been given a list of creatures and their descriptions. The different characteristics, behaviors, and habitats of the creatures can be used in the dichotomous key to differentiate among them.

    Creature Description
    Jackelope Mean-spirited horned jack rabbit
    Chupacabra Reptilian creature covered in scales with spines along the dorsal ridge; likes to eat goats
    Altamaha-ha Water monster with an alligator-like head and long neck; lives in the marshes of Coastal Georgia
    Sasquatch Stinky giant humanoid covered in brown fur; found in the forests of North America
    Yeti Giant mountain humanoid covered in white fur; prefers the snow
    Kraken Giant octopus-like creature; takes down ships in the open ocean
    Nessie Water monster with a snake-like head and long neck; lives in Loch Ness, in the Scottish highlands

    Below, you will find the dichotomous key used to identify a folkloric creature you may come across. On the left is the list of questions and on the right, the same list is represented as a flowchart. Both are useful representations of the same dichotomous key.

    1. Does the creature live on land? clipboard_e3fac41895ac6a98c1b96149d502dbc49.png

    • a. Yes: go to question 2
    • b. No: go to question 5

    2. Does the creature resemble a human?

    • a. Yes: go to question 3
    • b. No: go to question 4

    3. Does the creature have brown fur?

    • a. Yes: Sasquatch!
    • b. No: Yeti!

    4. Does the creature have scales?

    • a. Yes: Chupacabra!
    • b. No: Jackelope!

    5. Does the creature have tentacles?

    • a. Yes: Kraken!
    • b. No: go to question 6

    6. Does the creature have a large head, resembling an alligator?

    • a. Yes: Altamaha-ha! clipboard_ed68ce620ea716b2d609625345cac3c8f.png
    • b. No: Nessie!

    Using the dichotomous key, identify the creature on the right.

    Part 2: Building a Dichotomous Key

    In the table below, there are several different emojis. Your job is to build a dichotomous key that would help distinguish among them. There is space in the table to write out a description of each emoji, if necessary, as well as a name for each. Record your question series in the space below.

    Emoji Description Name

    Dichotomous Key Questions:


    Part 3: Using a Dichotomous Key to Identify Trees

    In this section, a dichotomous key will be used to identify tree species based on samples provided by your instructor. Refer to the guide provided should any terms about the characteristics used to distinguish among trees be unfamiliar.

    Plant Number Scientific/Common Name
    Plant 1  
    Plant 2  
    Plant 3  
    Plant 4  
    Plant 5  
    Plant 6  
    Plant 7  

    This page titled 1.2: Taxonomy is shared under a CC BY-SA 4.0 license and was authored, remixed, and/or curated by Susan Burran and David DesRochers (GALILEO Open Learning Materials) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.