Classification of organisms



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Biology 1001 Laboratory 8

CLASSIFICATION OF ORGANISMS

PREPARATION

-Read this exercise before you come to lab.

-Bring your drawing paper and pencil.

-Remember to take your lab coat today.


TEXTBOOK READING

Biology (Campbell et al.)- Chapter 26, pg. 536-544.


OBJECTIVES
After completing this laboratory, the student should be able to:
l. Name the seven commonly used levels in the system of biological classification.

2. Identify the parts of a scientific name and write them with proper protocol.

3. Use a dichotomous key to identify correctly the genus and species names of a series of organisms.

4. Construct a dichotomous key to aid in identifying a series of organisms.

5. If given a representative organism, name the kingdom and phylum for that organism.

6. Learn to make a proper biological drawing.



LABORATORY ASSIGNMENTS
l. Using the appropriate dichotomous key, identify the organisms given to you.

2. Construct a dichotomous key for a set of organisms given to you.



3. Make a biological drawing of a shell and pass in for evaluation before you leave the lab today.

4. Answer the questions on the assignment page.



A. INTRODUCTION
SOME USEFUL DEFINITIONS:
Systematics: The scientific study of the kinds and diversity of organisms and the evolutionary relationships between them.
Taxonomy: The delimitation of biological groups.
Classification: The arranging of organisms into related groupings -- often in a hierarchical system.
Nomenclature: The naming of organisms. It consists of producing a type specimen, a name in Latin and a published description in a scientific journal.
Organisms are named according to an International Code of Nomenclature. They are classified according to the insight and prevailing conventions of active biologists. It should be pointed out and stressed that there is as yet no perfect or ideal system of classification which is satisfactory to all taxonomists.
B. THE TAXONOMIC HIERARCHY
There are seven commonly used levels to the system of biological classification used today:

Kingdom
Phylum (plural: Phyla)

Class

Order


Family

Genus (plural: Genera)

species (plural: species)
Notice that the word ‘Genus’ begins with a capital letter and is italicized. The names of genera are always capitalized and italicized. Notice also that the word ‘species’ begins with a lower case letter and is italicized. All species names begin with lower case letters and are italicized. You may also see genus and species names underlined – this is also acceptable in place of italicizing.

Here are two examples showing the complete classification and the proper scientific names. The first is for an animal, the sea scallop, the one you find on restaurant menus.


Kingdom Animalia

Phylum Mollusca

Class Pelecypoda

Order Mytiloida

Family Pectinidae

Genus Placopecten

Species magellanicus (Gmelin)

The second example is for the sugar maple tree, the one that gives sap used to make maple syrup.


Kingdom Plantae

Phylum Anthophyta

Class Dicotyledonae

Order Sapindales

Family Aceraceae

Genus Acer

Species saccharum Marsh.

If the name of the species is not known the name of the Genus is sometimes followed by the abbreviation "sp." which is in lower case letters and not underlined. For example, Acer sp. refers to a maple tree in general without stating whether it's a sugar maple, Acer saccharum, a red maple, Acer rubrum or any other particular kind of maple.


A Genus name is sometimes abbreviated by giving only the first capital letter of the latinized name, but only after it has been established which Genus name is being referred to. For example, in a general discussion about several kinds of maple trees, you could say ‘the red maple, Acer rubrum, has distinctly red leaves, while A. saccharum has green leaves.’ It is very clear in this instance that the ‘A’ refers to the previously mentioned genus of Acer. The name of the species is never used alone without either the name of the genus or the initial of the name of the genus preceding it.


Sometimes, after the scientific name, you will see another name or initial that is not underlined or italicized (or it may be in brackets). This is the name or initial of the authority or person who named the organism. Carolus Linnaeus, the father of taxonomy, named many of the plants and animals that we see every day. The name Linnaeus is so often placed after the species name that it is frequently abbreviated to L. In general, this is the only authority name that is well known enough for an abbreviation.
You may sometimes see a second underlined or italicized name after the species name. This is the subspecies name and distinguishes the race or subspecies of an organism.
Example: American Robin
Turdus migratorius migratorius Linnaeus

Genus species subspecies authority


There are several different types of classification whose differences are based on the kind of characteristics used:
l. Natural classification uses many features of the organisms involved, judging none to be particularly crucial.

2. Artificial classification is based only on those characters defined by a biologist to be important. "Importance" is based on the purpose of the classification, e.g. colour is important for a list of sponges in Bermuda, based on their colour for use by tourists.

3. Phylogenetic classification is based only on ancestry. Organisms with a common ancestor are in the same group.
No matter what characters are used, there are usually too many organisms in a taxon for the ordinary biologist to remember by memory. Therefore, some of the most useful tools for a biologist are the authoritative keys that have been constructed to aid in the identification of specimens. There are keys for practically any group of interest.

Keys are developed by using similarities and differences in characteristics or traits. Characteristics named in keys may be physical, behavioural, and even biochemical, but they must be observable and describable. These characteristics are given in pairs of opposing statements. Only one statement in each pair can be true for the given specimen. The term dichotomous comes from dichotomy meaning “two opposites or categories”. After reading these two opposite statements, the observer must make a choice as to which most accurately describes the specimen. The statement chosen directs the observer to another pair of statements in which another choice must be made. Each succeeding pair of statements is more specific in describing the specimen. Choices are continued until the specimen is identified and named. Generally, taxonomic keys call attention to the small details of things to be identified.


To use this kind of key, look at the object being identified, then, starting with number 1 in the key, select the one of the pair of choices that best describes your specimen. At the right hand side of the key are the numbers which will lead to another set of choices, from which another choice must be made. Thus each step leads to another step and its alternatives until a name is reached.
Here is a brief example of using a key:

This is the object to be identified:




l. a. Has leaves........................................................................................PLANT

b. Does not have leaves.........................................................................go to 2

[Does the specimen have leaves? No. Therefore choose b and go to step 2.]


2. a. Has fur.............................................................................................CAT

b. Does not have fur..............................................................................go to 3

[Does it have fur? No. Therefore go to step 3.]
3. a. Has hard wings, six legs....................................................................BEETLE

b. Lacks wings, has eight legs................................................................TICK

[Eventually, by following the steps and eliminating choices, the specimen is identified as a beetle.]
LABORATORY ASSIGNMENT 1
You and your lab partner have been given several different mollusc shells and several conifer branches to identify. Use the keys on the following pages. Proceed with one shell or branch at a time and follow the directions in the key until you come to the genus and species name of the specimen. You will find it helpful to consult Figure 8.1, the anatomy of mollusc shells on page 8-7 and the Glossary of terms on page 8-8, and figure 8.2, diagrams of the conifer twigs on page 8-11.
Record your final identification on the assignment sheet at the back of this outline. Enter both the correct scientific name and the common name in the table. Don't forget the rules about the use of capital and small letters and about the underlining of scientific names. (HINT - the authority is part of the scientific name.)

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KEY TO THE MOLLUSC SHELLS


1.a. Shell is flat, not obviously spiral.................................................................go to 2
1.b. Shell is obviously spirally coiled ..................................................................go to 9
2.a. Shell with an internal cup or shelf.........................................................go to 3
2.b. Shell without an internal cup or shelf....................................................go to 4
3.a. Shell with an internal cup-shaped process inside; circular; up to 25 mm; slightly twisted centre apex; colour pinky-white streaked with brown...................................Crucibulum striatum Say (cup and saucer limpet)
3.b. Shell with wide, slightly concave internal shelf; oval up to 50 mm; apex on one side; grey-white to tan, often with blotches of red-brown; white or buff inside......................Crepidula fornicata L (slipper limpet)

4.a. Hinge wings present ....................................................................................go to 5


4.b. Hinge wings absent ......................................................................................go to 7
5.a. Hinge wings about equal ...................................................................go to 6
5.b. Hinge wings distinctly unequal; radiating ridges relatively coarse

....................................Chlamys islandicus Muller (Iceland scallop)


6.a. Shell is prominently fluted, flutes evident on inside; shell is translucent

..............................Aequipecten irradians Lam. (bay scallop)


6.b. Shell is relatively smooth, not fluted; radiating ridges are numerous and fine

....................Placopecten magellanicus Gmelin (sea scallop)


7.a. Shell length is about 6 times the width; thin elongate shell, up to 250 mm; surface smooth ..........................................Ensis directus Conrad (razor clam)
7.b. Shell length much less than 6 times the width.........................................................go to 8
8.a. Wedge-shaped shell, up to 80 mm, regular growth lines; blue-black exterior, shiny interior .......................................Mytilus edulis L (blue mussel)
8.b. Irregularly shaped, rough and heavy shell; grey-white exterior; interior dull white with nearly central violet muscle scar............Crassostrea virginica Gmelin (common oyster)

9.a. Siphonal canal present .............................................................................go to 10


9.b. Siphonal canal absent ...............................................................................go to 12
10.a. Siphonal canal long with a twist; distinct decorations on shell-vertical waves

or spiral cords; outer lip not thickened; shell larger than 45 mm......................go to 11


10.b. Siphonal canal short and straight; shell solid and sturdy with thickened outer lip, may

have pupoidal teeth; no larger than 30 mm; no distinct lines or decorations; colour is variable,

grey, white, yellow, brown, orange, may be banded ..................Thais lapillus L (Atlantic dogwinkle)

11.a. Shell solid with wavy vertical folds or undulations; up to 110 mm; 6-8 whorls; apex; aperture large; colour grey or greenish, interior yellowish to tan or.................................................................Buccinum undatum L (waved whelk)


11.b. Shell has 7-10 distinct raised brown spiral cords; up to 140 mm; inside aperture is white with brown cords showing faintly through................Neptunea decomostata Say (ten-ridged whelk)
12.a. Umbilicus present .................................................................................go to 13
12.b. Umbilicus absent ..................................................................................go to 14
13.a. Globose shell; umbilicus deep and round; parietal wall uniformly thin; outer lip not thickened; outer lip meets body whorl at a sharp angle; up to 120 mm. Colour is dirty-white to brownish-grey .......................Lunatia heros Say (northern moon snail)
13.b. Parietal wall thickened at the juncture of outer lip and body whorl; outer lip meets body whorl at a moderate angle; up to 35 mm; has spiral bands of bluish or reddish spots...............................Lunatia triseriata Say (spotted northern moon snail)

14.a. Shell globular, as wide as it is high; up to 13 mm; shell is smooth and shiny, spire slightly depressed. Colour uniformly brownish-yellow; columella whitish............................................Littorina obtusata L (northern yellow periwinkle)


14.b. Shell oval, longer than it is wide, up to 40 mm, spire slightly elevated. Colour grey to brownish-grey with spiral dark lines; columella and inner lip whitish, outer lip dark.............................................................Littorina littorea L (common periwinkle)

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