LABORATORY EXERCISE #4

CLASSIFICATION OF LIFE

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. Write a scientific name correctly.

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

5. Identify organisms by using a dichotomous identification key.

REFERENCE

Textbook:   chapter 14

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 that 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 totally useless to you; you can't find anything you need.  Lucky for us, when we examine a large number of things, like books or groceries in the supermarket, someone has usually classified them and grouped them based on their similarities.

Taxonomy is a field that deals with the classification and naming 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 day.  We must have a system to make sense of it all.  We depend on taxonomy to give us information about each organism.  Theoretically, if you know the group to which an organism is a member, you will know something about the specific 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 Carl Linnaeus, a Swedish botanist.  He developed the first "natural system" of classification which attempts to show the degree of relationship among different organisms, and is based on structural similarities.  He also devised a system of naming organisms, called binomial nomenclature, which assigns two names to each organism.

The current version of Linnaeus' natural system of classification is one that separates all living things into five large groups called Kingdoms -- Plants, Animals, Fungi, Protista (single celled organisms), and Monera (bacteria).  Each kingdom is subdivided and further subdivided until you reach the group called a species which is basically an interbreeding group that produces offspring like itself.

It is especially important for us to know man's 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 superior intelligence)

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

Genus  Homo   (tool-using hominids with big brains)

              Species  Homo sapiens   (only surviving species of genus Homo)

Note that the kingdom is the broadest category.  It includes many members.  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 which are dead languages; they are accepted world-wide; they are not regional; and not just anyone can make one up.  Common names are fleeting, not as descriptive, and often 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.

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.  The dichotomous 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.

Define “taxonomy.”

What is Carl Linnaeus’ contribution to biology?

What is “binomial nomenclature?”

Define “species.”

Activity:

Use a Dichotomous Key to Identify Animals

As a simple example to help you understand how an identification key works, let’s 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.

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

To locate and identify the dog you proceeded through this path:   1a, 2b, 3b  

What path did you take to locate the earthworm?

To identify the clam you took what path? 

All of the following dog characteristics can be determined from this key:

a.  internal skeleton

b.  does not lay eggs; gives live birth

c.  does not have fins

Describe all of the characteristics of the octopus that can be determined from this key:

Describe all of the snail characteristics which can be determined from this key:

Your instructor will provide several sample representatives from various animal taxa.  Using the simple dichotomous key below, identify each sample to the most specific taxon possible.

A SIMPLE KEY TO SOME ANIMAL GROUPS
1A.	Animal has internal skeleton - Phylum Chordata	19
1B.	Animal has external skeleton or no apparent skeleton	2
2A.	Irregular-shaped body; porous - Phylum Porifera (e.g., sponges)
2B.	Regular-shaped body (symmetrical)	3
3A.	Radial symmetry (pincushion pattern)	4
3B.	Bilateral symmetry (similar right and left body halves)	6
4A.	Arms extend from a central disc, or spines present - Phylum Echinodermata
4B.	Soft body; little or no color - Phylum Cnidaria	5
5A.	Saucer-shaped transparent body with small tentacles - Class
	Scyphozoa (e.g., jellyfish)
5B.	Barrel-shaped body; tentacles at one end - Class Anthozoa
	(e.g., sea anemone)
6A.	Hard outer covering or tentacles or antennae present	10
6B.	Wormlike body	7
7A.	Flattened specimen - Phylum Platyhelminthes	8
7B.	Cylindrical specimen	9
8A.	Smooth, nonsegmented body - Class Trematoda (e.g., liver fluke)
8B.	Segmented body - Class Cestoda (e.g., tapeworm)
9A.	Nonsegmented colorless body – Phylum Aschelminthes (Nematoda) (e.g., intestinal roundworm)
9B.	Segmented body - Phylum Annelida (e.g., earthworm)
10A.	Body has jointed legs - Phylum Arthropoda	14
10B.	Soft body has no jointed legs - Phylum Mollusca	11
11A.	Shell not present; tentacles present	12
11B.	Shell present	13
12A.	Appears as snail without shell - Class Gastropoda (e.g., slug)
12B.	Tentacles and eyes present - Class Cephalopoda (e.g., squid)
13A.	Bivalved shell (two halves) - Class Pelecypoda (e.g., clam)
13B.	Univalved shell (single unit) - Class Gastropoda (e.g., whelk)
14A.	Jointed appendages on most body sections	15
14B.	Jointed appendages on certain body segments; not all appendages are legs	16
15A.	One pair of legs per body segment - Class Chilopoda (e.g., centipede)
15B.	Two pairs of legs per body segment - Class Diplopoda (e.g., millipede)
16A.	Two pairs of antennae; large claws - Class Crustacea  (e.g., fiddler crab)
16B.	No large claws	17
17A.	Four pairs of legs; no antennae or wings - Class Arachnida (e.g., spider)
17B.	Three pairs of legs; wings present - Class Insecta (e.g., mud dauber wasp)
18A.	Arms present; body surface knobby - Class Asteroidea (e.g., stars)
18B.	Many-spined animal; resembles a pincushion - Class Echinoidea (e.g., sea urchin)
19A.	Fishlike with fins	20
19B.	Not fishlike without fins	21
20A.	Body flattened; long lancelike tail- Class Chondrichthyes (e.g., stingray)
20B.	Scales present; tail not lancelike - Class Osteichthyes  (e.g., sea bass)
21A.	Claws usually present; scales; zero or four legs - Class Reptilia (e.g., snake)
21B.	Claws either present or absent; no scales	22
22A.	Claws absent - Class Amphibia (e.g., eastern spotted newt)
22B.	Skin covered with feathers or hair	23
23A.	Feathered; claws present - Class Aves (e.g., bald eagle)
23B.	Hair present - Class Mammalia (e.g., dog)

Use a Dichotomous Key to Identify Selected Tree Species

If the season of the year is accommodating and if weather permits, your instructor will take the class outdoors to key out some of the trees on the VSCC campus.

A LEAF KEY TO SELECTED TREE SPECIES ON THE VSCC CAMPUS
1A	Trees with needle‑like leaves	2
1B	Trees without needle‑like leaves	6
2A	Leaves in bundles of two or more	3
2B	Leaves occurring individually	4
3A	Leaves in bundles of 5; main branches whorled  Pinus strobus (white pine)
3B	Leaves in bundles of 3 . . Pinus taeda (loblolly pine)
4A	Leaves yellow‑green and soft Taxodium distichum (bald cypress)
4B	Leaves not yellow‑green nor soft	5
5A	Leaves blue‑green   Picea pungens (blue spruce)*
5B	Leaves green Picea abies (Norway spruce)**
6A	Leaves fan‑shaped with two lobes; veins roughly parallel Ginkgo biloba (ginkgo)**
6B	Leaves not as above	7
7A	Leaves compound	8
7B	Leaves simple	13
8A	Whole leaves opposite on the twig Fraxinus americana (white ash)
8B	Whole leaves alternate on the twig	9
9A	Leaves once pinnately compound	10
9B	Leaves twice pinnately compound	12
10A	Base of leaf stalk conceals a lateral bud (remove leaf from  twig to check for hidden bud) Cladrastis lutea (yellowood)
10B	Lateral bud not concealed by petiole	11
11A	Twigs have chambered pith (cut twig longitudinally through the pith); crushed leaves smell like green walnuts Juglans nigra (black walnut)
11B	Pith not chambered; leaves don't smell like green walnuts Robinia pseudoacacia (black locust)
12A	The compound Leaf subdivided into more than 300 leaflets Albizia julibrissin (mimosa)**
12B	The compound leaf is subdivided into less than 300 leaflets Gleditsia triacanthos (honeylocust)
13A	Leaves in a whorled arrangement (3 per node)Catalpa bignonioides (southern catalpa)
13B	Less than 3 leaves per node	14
14A	Leaves opposite on the twig	15
14B	Leaves alternate on the twig	19
15A	Leaves toothed and palmately veined	16
15B	Leaves entire and pinnately veined	18
16A	Leaves deeply 5‑lobed; white to silvery beneath; flaky bark Acer saccharinum (silver maple)
16B	Characteristics not as above	17
17A	Flowers appear before leaves; young fruits are red; leaves usually 3‑lobed; teeth small Acer rubrum  (red maple)	17A
17B	Flowers appear as the leaves expand or after; leaves 5‑lobed and have large teeth Acer saccharum (sugar maple)	17B
18A	Leaf veins curve inward strongly close to the margin; leaves rarely more than 3.5 inches long at maturity; leaf base rounded  Cornus florida (flowering dogwood)
18B	Leaf veins don't curve inward strongly; leaves more than 3.5 inches long at maturity; leaf base      tapered Chionanthus virginicus (fringe tree)
19A	Leaves entire	20
19B	Leaves toothed and/or lobed	24
20A	Leaves heart‑shaped Cercis canadensis (redbud)
20B	Leaves not heart‑shaped	21
21A	Leaves large, thick and evergreen; a stipular scar encircles the twig at each node  Magnolia grandiflora (southern magnolia)
21B	Leaves deciduous; stipular scars absent	22
22A	Leaves not clustered at tips of twigs; main limbs at right angles to the trunk Nyssa sylvatica (blackgum)
22B	Leaves clustered at tips of twigs; fruit an acorn	23
23A	Leaves less than one inch wide Quercus phellos (willow oak)