CLASSIFICATION OF LIFE                                      Laboratory Exercise # 5

                                                                                                                                  

 

 

LABORATORY OBJECTIVES

 

Upon completion of this laboratory, the student will be able to:

 

1. Identify or define the following:  taxonomy, Linnaeus, binomial nomenclature, species.

 

2. Classify the human species within the seven categories in the classification system..

 

3.  Identify organisms by using an Identification Key.

 

4. Devise a classification system for a group of objects.

 

 

MATERIALS NEEDED

 

Any one of the following:

      A box of various baseball or football cards

      A cupboard full of canned goods and dry goods

      A coin collection

      A bookshelf with a wide variety of books

      A CD or tape collection

 

Ruler (metric)

          Textbook

PREPARATION

 

Read the pages in the text on Taxonomy (naming and classifying organisms).

 

 

INTRODUCTION

 

Suppose you visit a library which is known for its wide variety of wonderful books.  But when you get there you find that the books are not arranged in any particular order, they are in total disarray.  How  will you ever do any research or find a book which you would like to read?  You might assume that you can at least look at the book titles and determine what each book is about, though this will take a very long time.  But, alas, you discover that none of the books have been named.  The vast collection is useless, you can't fine anything you need.  Lucky for us, when we examine a large number of things, like books or groceries in the supermarket, someone has usually named them and classified them (grouped them based on their similarities).

 

Taxonomy is a field which deals with the naming (nomenclature) and classification of organisms.  Classification of life involves the placement of organisms into groups (taxa) and is based on structural similarities.  It is assumed that if two different organisms have many structures in common (e.g., a red fox and a grey fox), they will have many genes in common; thus, they will be closely related genetically and perhaps placed in the same family.  However, if two organisms are very different structurally (e.g., a bald eagle and a red fox) they will have fewer genes in common and will not be put in the same family, but might be placed together in a broader taxonomic group such as a phylum.  Until recently, only large structural characteristics were used by taxonomists for classifying organisms. But now, very small features such as cellular organization, biochemistry, and chromosome number and structure are also used in taxonomy.

 

There are probably more than five million species of organisms on Earth.  At least 1 1/2 million of these organisms have been named and classified already and others continue to be described each year. By far most are insects.  A biologist once observed “God must be inordinately fond of beetles”.  We must have a classification system to make sense of it all.  We depend on taxonomy to give us information about each organism. The idea is that if you know the group to which an organism is a member, you will know something about that organism.  Classification is also necessary so that we can communicate to others about the different kinds of organisms.

 

Our modern system of classification of life was developed by Carolus Linnaeus, a Swedish botanist.  He developed the first good system of classification based on structural similarities. He also devised a system of naming organisms, called binomial nomenclature, which assigns two names to each organism.  Our modern classification of organisms is said to be a “natural system” of classification since it attempts to show the degree of relationship among different organisms. The modern system of classification separates all living things into five large groups called Kingdoms -- Plants, Animals, Fungi, Protista, and Monera (mostly bacteria).  Each kingdom gets subdivided and further subdivided until you reach the group called a species which basically is an interbreeding group that produces offspring like itself.

 

It is especially important to know our own position in the classification system.  Homo sapiens is classified as follows:

 

Kingdom  Animalia   (multicellular organisms that eat other organisms; mostly mobile)

 

   Phylum  Chordata   (animals with a semi-rigid rod, a notochord, running down its back)

 

      Class  Mammalia   (chordates with hair and mammary glands)

 

                     Order  Primates   (mammals with well-developed hands and a high level of  intelligence)

 

Family  Hominidae   (primates which walk upright on two legs, hands well structured for

                                                           manipulating objects; cerebrum of the brain is relatively large)

 

    Genus  Homo   (tool-using hominids with very large brains)

 

         Species  Homo sapiens  (only surviving species of genus Homo)

 

 

Note that the kingdom is the broadest category which includes many members, and that the species is the most  specific group.

 

Binomial nomenclature is used to issue scientific names. The scientific name gives us some information about the organism.  And, much like a person's last and first name, gives a relationship name and a specific name.  The first name is the generic (genus) name and the second is specific.  For example, Quercus alba refers to the species commonly known as white oak.  The scientific name actually says --"Oak, white".  Thus, it is in the genus for oaks, and this particular species is white oak.  Scientific names are more useful than common names because they are in Latin or Greek, unchanging dead languages; they are accepted world-wide; they are not regional. Common names are often fleeting, not as descriptive, and may lead to false assumptions.  Liriodendron tulipifera is commonly known as tulip poplar, tulip tree, yellow poplar, and poplar.  It is not really a poplar at all, but is in the magnolia family. Many times there will be several common names for one species but there is normally only one accepted scientific name for a species.

 

It is not always easy to identify organisms.  Sometimes the differences between two species of organisms are very slight.  Biologists use identification keys to help them identify organisms.  Usually an identification key is made up so that as you read it you have two choices for each characteristic listed.  There could be a key to broadleaf tree species where you have to decide whether a tree has simple or compound leaves.  Each choice you make in the identification key leads you to further choices more specifically identifying the organism.  Eventually the organism is "keyed out" or named.  You already have had some practice using a tree key.

 

 

ACTIVITIES:

 

 

A.    Identification Key to Selected Animals

 

As a simple example to help you understand how an identification key works, lets examine a simple key to certain familiar animals:  earthworm, grasshopper, dog, octopus, fish, snail, lobster, clam, alligator, bird, and frog.  As you proceed, especially note how the animals are grouped according to their similarities.  To make this exercise realistic, you must pretend that you have the organism before you but that you do not know what it is.  Start at number 1 and select either a or b.  Follow to the next number as you are instructed and again select a or b.  Proceed until you come to the name of the animal.  Demonstrate your understanding by answering all follow-up questions and reporting this activity on Report Sheet 1

 

 

IDENTIFICATION KEY TO SELECTED ANIMALS

 

 

    Next Move or

Choice               Characteristic                                                                           Identification

 

1a         The animal has a bony internal skeleton                                                  2

1b         The animal has an external skeleton or no skeleton at all                          6

 

2a         The animal has fins                                                                                Fish

2b         The animal does not have fins                                                                3

 

3a         The animal lays eggs                                                                             4

3b         The animal does not lay eggs; live birth                                                   Dog

 

4a         The animal lays shelled eggs on land (not in water)                                  5

4b         The animal lays eggs without shells in water                                            Frog

 

5a         The animal has wings                                                                            Bird

5b         The animal does not have wings                                                             Alligator

 

6a         The animal has a soft body with no external skeleton                               7

6b         The animal has an exoskeleton or a shell covering the body                      8

 

7a         The animal has eight arms (tentacles)                                                     Octopus

7b         The animal has no arms                                                                         Earthworm

 

8a         The animal has a jointed exoskeleton                                                      9

8b         The animal has a shell, but not a jointed exoskeleton                                10

 

9a         The animal has six legs                                                                          Grasshopper

9b         The animal has more than six legs                                                          Lobster

 

10a       The animal has a coiled shell                                                                  Snail

10b       The animal has a hinged double-shell; shell not coiled                               Clam

 

 

 

B.        Classifying Your Own Collection

 

In this activity you will classify and arrange your own personal collection.  You may choose a bookshelf with a wide variety of books, a box full of baseball (or football) cards, a cupboard full of canned goods and dry goods, a CD or tape collection, or a jumbled up coin collection.  With the permission of your instructor you may choose another chaotic collection of your own.  The idea is to make order out of chaos by classification and arrangement.  In actually physically arranging the collection, keep in mind the way a dichotomous (branching into two choices) identification key is designed.  Always choose between two opposing characteristics each time.  Do not use meaningless characteristics in your classification scheme; e.g., color of uniforms, color of books, size of books, condition of coins, CDs that you hate, etc

 

 

You will need to mark and copy  the worksheet below; then paste it in a Word; then answer the questions; then save the document and email it to me as an attached Word  file.