AV:   TAXONOMY

                                                                          LAB 9

                                                                    TAXONOMY

 

 

Taxonomy is a field which deals with the classifying and naming of organisms.  Classification involves the placement of organisms into groups (taxa) and is based mainly 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 would have many genes (a gene is a segment of a DNA molecule) in common; thus, they would be closely related genetically and placed in the same family.  However, if two organisms are very different structurally (e.g., a bald eagle and a red fox) they would have fewer genes in common and would not be put in the same family, but might be placed together in a broader taxonomic group such as a phylum.  Until recently, only macroscopic (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.

 

The classification system used in your text is a "natural system" -- it attempts to show the degree of relationship among the different organisms, and it is based mainly on structural similarities.  Biologists call these structural similarities "homologies".

 

Question 1:         Genes determine the structure of an organism.  Chemically, what is a gene?  (refer to your text). 

 

Question 2:         Birds, reptiles and mammals are placed in the same phylum; name this phylum.  (refer to the Appendix in your text)

 

Question 3:         In addition to large structural characteristics, what other features may be used to classify organisms? 

 

Question 4:         Define "natural system of classification". 

Nomenclature involves the assigning of a scientific name to each species.  Carolus Linnaeus devised the binomial (two-name) system of nomenclature in the eighteenth century.  He gave scientific names to many plant and animal species.  The human species has this scientific name, Homo sapiens.  Every scientific name is in Latin (an unchanging language) and consists of a genus which is capitalized and a specific name (species) that is not capitalized.  Also, the scientific name is underlined or in italics.  The Latin name for white pine is Pinus strobulus and the name for Virginia pine is Pinus virginiani.  Two or more species may have the same generic name if they are closely related.

 

Question 5:         Define "species".  (refer to your text) 

 

Question 6:         The generic name for man is Homo; what is the specific name?

 

Question 7:         There is only one species of man living today, but another species named Homo                                             existed over 300,000 years ago and was ancestral to our species.  (refer to text)

 

Question 8:         All species of pine trees have the same generic name which is

                                                                 .

 

It is especially important for us to know man's position in the classification system.  Homo sapiens is classified as follows:

 

Kingdom Animalia (multicellular eukaryotes that eat other organisms; most are mobile)

 

   Phylum Chordata (animals with a notochord)

 

      Class Mammalia (chordates with hair and mammary glands)

 

         Order Primates (mammals with well-developed hands and superior intelligence)

 

            Family Hominidae (primates which walk upright legs, hands well-structured for manipulating objects)

 

               Genus Homo (tool-using hominids with big brains)

 

                  Species Homo sapiens (only surviving species of Homo)

 

    Note that the kingdom is the broadest category which includes many members, and that the species is the most specific group.  However, even the species is sometimes subdivided into subspecies if there is significant variation in two or more populations of a species.  Actually, the complete name for man is Homo sapiens subspecies sapiens while the extinct Neanderthal Man is called Homo sapiens neanderthalensis.  In the past these two subspecies of man coexisted, but finally Homo sapiens sapiens emerged as the only surviving human population.

 

Question  9:        What is a eukaryote?  (refer to text) 

 

Question 10:       What is a notochord?  (refer to text) 

 

Question 11:       Homo sapiens is placed in what order? 

 

The author of your text uses a 5-kindgom classification system; these kingdoms are; (1) Monera, (2) Protista, (3) Fungi, (4) Plantae, and (5) Animalia.

 

Question 12:       Referring to the Appendix in your text, list the characteristics of each kingdom. 

 

Question 13:       Referring to  your text, give one example of each kingdom.

 

Question 14:       Which came first, Monerans or Protistans? 

 

Question 15:       Given the following groups of organisms, pick the pair which are most closely related:  blue-green algae, nematodes, green algae, club fungi, sea stars, reptiles, lobsters, and birds.

                   Thus far, about two million species of organisms have been named and classified, but biologists estimate that there may be that many more which have not yet been found. Undoubtedly, there are thousands of undiscovered species in the depths of oceans and in other remote places on earth.  Taxonomists must also name and classify prehistoric species which became extinct; these organisms are known only from their fossilized remains.  Unfortunately, the fossil record is sketchy; in some cases, a few pieces of bones or imprints in rocks are the only materials the biologist has for classifying extinct organisms.

 

There is a tendency for beginning biology students to think that all organisms can be neatly pigeon-holed into taxonomic groups.  But, not all organisms are easily classified.  One problem for the taxonomist is that organisms change through time (evolve).  Note the evolution in the dog species.  Many breeds of dogs occur today, yet they all evolved from one type of wild dog that lived only a few thousand years ago.  It is possible that in the future some of these breeds of dogs will have diverged so much that they will be reproductively isolated.  If that happens, separate species of "dogs" will exist.  Millions of years from now, there will be some new species on earth.  What will the "human species" be like one million years from now -- how will our descendents classify themselves then?

 

LAB OBJECTIVES:

 

1.                To learn some basic concepts of taxonomy.

 

2.                To use a dichotomous key to identify several animal specimens.  While keying the various animals, the student will become familiar with the classification characteristics of each organism being identified.

 

3.                To identify various trees on the VSCC campus using a dichotomous key (weather permitting).

 

ACTIVITIES:

 

1.                View the video tape on TAXONOMY.

 

2.                Your instructor will show you how to use a dichotomous (forking) key.  A simple key to some members of the animal kingdom is provided.  Begin at step one of the key for each specimen that has been set up in the lab.  Identify the taxon of the animal at each station.  Remember, the purpose is to become familiar with the classification characteristics of the organisms you are identifying.  Hint: You may be given an organism and a copy of the following taxonomic key to use on your next lab exam.  Make sure you can use this key successfully before leaving lab.

 

                   Number a blank sheet of paper as directed by your instructor.  Use the taxonomic key provided to determine the taxon (phylum and/or class) to which each organism belongs.  Record this information beside the appropriate number.

 

3.                Weather permitting, your instructor may take you outside to practice using a dichotomous key with some campus trees. Together you will key out several specimens to learn to use the key.  You will then key out the other trees noted on the campus map.  Handouts will help you with leaf structure, shapes, margins, venation, etc.

 

4.                Study the herbarium specimens provided for practice with new information (i.e., simple leaf vs. compound leaf, etc.)

                                                   

 

 

In North America, there are 652 native tree species and over 100 commonly encountered species introduced from other countries.  How many of these could you identify in the field?  Coniferous (cone-bearing) trees dominate the forests of Canada and other cold areas.  Many deciduous (leaf-losing) tree species are found in the forests of the eastern United States and other temperate regions.  Palms, mangroves, and other tropical evergreen species occur in Florida and other parts of the world which are warm and moist year-round.  In our yards, parks, and orchards we have planted hundreds of exotic species.  Trees provide us with fuel, construction materials, furniture, paper, fruits, oxygen, shade, and other benefits.  Considering our dependence on trees, it follows that we should be interested in them.  At least we should learn the common names of some of the tree species which grow in our area.

 

Question 16:         What is dendrology?

 

Question 17:         What is a conifer? 

 

Question 18:         Most conifers are evergreen, but a few are deciduous (shed all their leaves in the fall); name one deciduous conifer.

 

Question 19:         Most trees in our area are angiosperms (flowering plants) and are deciduous.  Name two local deciduous trees which are angiosperms. 

 

Question 20:         List 8 important things provided by trees.