Organism Classification Example Essay

People who live close to nature usually have an excellent working knowledge of the elements of the local fauna and flora important to them and also often recognize many of the larger groups of living things (e.g., fishes, birds, and mammals). Their knowledge, however, is according to need, and such people generalize only rarely.

From the Greeks to the Renaissance

The first great generalizer in classification was Aristotle, who virtually invented the science of logic, of which for 2,000 years classification was a part. Greeks had constant contact with the sea and marine life, and Aristotle seems to have studied it intensively during his stay on the island of Lesbos. In his writings, he described a large number of natural groups, and, although he ranked them from simple to complex, his order was not an evolutionary one. He was far ahead of his time, however, in separating invertebrate animals into different groups and was aware that whales, dolphins, and porpoises had mammalian characters and were not fish. Lacking the microscope, he could not, of course, deal with the minute forms of life.

The Aristotelian method dominated classification until the 19th century. His scheme was, in effect, that the classification of a living thing by its nature—i.e., what it really is, as against superficial resemblances—requires the examination of many specimens, the discarding of variable characters (since they must be accidental, not essential), and the establishment of constant characters. These can then be used to develop a definition that states the essence of the living thing—what makes it what it is and thus cannot be altered; the essence is, of course, immutable. The model for this procedure is to be seen in mathematics, especially geometry, which fascinated the Greeks. Mathematics seemed to them the type and exemplar of perfect knowledge, since its deductions from axioms were certain and its definitions perfect, irrespective of whether a perfect geometrical figure could ever be drawn. But the Aristotelian procedure applied to living things is not by deduction from stated and known axioms; rather, it is by induction from observed examples and thus does not lead to the immutable essence but to a lexical definition. Although it provided for centuries a procedure for attempting to define living things by careful analysis, it neglected the variation of living things. It is of interest that the few people who understood Charles Darwin’s Origin of Species in the mid-19th century were empiricists who did not believe in an essence of each form.

Aristotle and his pupil in botany, Theophrastus, had no notable successors for 1,400 years. In about the 12th century ce, botanical works necessary to medicine began to contain accurate illustrations of plants, and a few began to arrange similar plants together. Encyclopaedists also began to bring together classical wisdom and some contemporary observations. The first flowering of the Renaissance in biology produced, in 1543, Andreas Vesalius’s treatise on human anatomy and, in 1545, the first university botanic garden, founded in Padua, Italy. After this time, work in botany and zoology flourished. John Ray summarized in the late 17th century the available systematic knowledge, with useful classifications. He distinguished the monocotyledonous plants from the dicotyledonous ones in 1703, recognized the true affinities of the whales, and gave a workable definition of the species concept, which had already become the basic unit of biological classification. He tempered the Aristotelian logic of classification with empirical observation.

Of all the various modes, classification/division essays are the easiest essay to organize according to a three part thesis statement (the five paragraph essay). Many teachers like the three part thesis because it has an obvious structure and is, therefore, easier to grade. However, there are some problems with it. First, not all essays lend themselves to three divisions. Secondly, students often force essays into artificial divisions in the attempt to create three divisions.

Classification/division essays lend themselves to the three part thesis for several reasons. First, a two part classification/division is often overly simplistic. Second, classifications or divisions that exceed five in number are often unwieldy to discuss within the limits of an essay.


The classification essay organizes supporting details into three or more groups with each group having its own identifying characteristics. For this reason, classification essays rely heavily on description and example as supporting details or evidence, description providing the means for identifying distinguishing characteristics and examples illustrating the members of each class. Classification essays may also use short narratives or anecdotes as evidence to support or illustrate a class.

Elements of Classification

There are three elements to a classification essay: the of things being classified, the (or principle of selection) for classifying the set, and the into which the set is divided.

Any set which is to be classified must share a common characteristic or be able to be distinguished from things outside the set. Biology classifies living organisms (non-living materials lie outside the set). Students, pets, vacation spots, or other generic nouns can serve as a set to be classified.

A scheme is the quality, standard, type, or function by which the elements of the set are sorted into classes, that is, the principle of selection for creating the groups. Biologists classify living organisms based on life processes and qualities. Geologists sort rocks into igneous, sedimentary, and metamorphic rocks, a classification based on how the rocks were formed. In order for a classification scheme to be effective it must be a significant, important, relevant, or valuable way to understand the set of things under consideration.

In general, when writing about each class, begin with an explanation of the descriptor, the characteristic which identifies the members of one class and differentiates the members of that class from the members of another class. Then include representative examples of the class. Often, a discussion of the class also includes an evaluation of the worth of this class or a comparison/contrast of this class to other classes within the scheme. Biologists frequently make reference to the ways in which members of a class are differentiated from members of other classes. For these reasons, modes which are used as methods within classification often include description, narration, definition, example, and comparison/contrast.

Set: Students
Scheme: Intensity of interest in school
Classes: Absent, Apathetic, Bored, Interested, Avid
Significance, Importance, Relevance, or Value: The amount of interest students take toward school may reflect the amount of interest they will take toward their work and life in general.

Organization of a Classification Essay

The introduction or lead-in to a classification essay will identify the set being classified and generally indicate the significance, importance, relevance, or value of the scheme being applied. The thesis statement frequently identifies the classes into which the set is being classified.

Topic sentences in classification essay body paragraphs should identify the class or group being considered and its relationship to the scheme for creating the classes. In classifying a set, more than one classification scheme may be possible, depending on why you are classifying the set and what can be gained from the classification scheme (its value); however, each essay should focus on one scheme for classifying the set.

Conclusions of classification essays often re-emphasize the significance, importance, relevance, or value of the scheme used to classify the set. Sometimes the conlusion will emphasize the most important grouping.


Confusing Modes: Sometimes students will confuse the classification essay with the example essay. Classification essays include examples, but the examples are given to illustrate the class. The class must be clearly defined and explained first, and then examples given as illustrations of the class.

Lack of Support: To be effective, each class must be clearly identified, using description to describe the unique characteristics of the class. Normally, each class should be a discreet group, that is, each member should only belong to one class. Also, when setting up classes, there should be more than one member in each class. Topic sentences in classification essay body paragraphs should identify the class or group being considered and how that group fits the scheme used to create the groups. Supporting sentences should describe the class or members of the class, give examples of members that fit the class, or tell stories about members of the class that show the members connection with the class.

In division essays, writers break down their subjects into parts for the purpose of understanding the subject. The relationship of these parts to the whole is then explained. Division essays often deal with systems and subsystems.

A division essay does not just break down a subject into a list of parts. For instance, an engine is made up of nuts, bolts, cylinders, gears, and other miscellaneous parts. But a division essay on a car would not focus on the individual pieces of the car but on the sub-systems of the car and how they relate to the whole. Like the classification essay, there are three elements to a division essay: the system, the principle of analysis, and the sub-systems.

For instance, in examining a car (system) to understand how it works (principle of analysis), a mechanic might divide the car into its separate subsystems: transmission, exhaust, electrical, engine, and so on. In order to understand the total system, the writer will need to explain how each sub-system functions, how it functions in relation to the other sub-systems, and how it functions in relation to the total system. To understand how a car uses energy (principle of analysis), a physicist might divide the total system into subsystems focusing on mechanical, chemical, and electrical energy.

One distinct difference between division essays and classification essays is that in classification essays, the members of each class must be distinct from the members of other classes (no item can be a member of more than one class). In division essays, individual parts might be members of more than one subsystem; however, the function of the part will be examined as it relates to each individual subsystem. For instance, the human body can be divided into subsystems that include the circulatory, the respiratory, and the excretory. The blood is an element of each of those systems, but its funtion is interpreted differently depending on the subsystem being discussed. Because division essays examine functionality, they frequently use process as a method. What distinguishes the division essay from the process essay is the focus on the interrelationship of processes both within subsystems and within the total system.

In addition to process, description, narration, and definition are frequent modes used as methods in division essays. Students should be careful not to confuse division with these other modes. Division essays identify the parts or subsystems of something in relation to the whole. Description or narration can be used to illustrate those parts or subsystems after the parts or subsystems have been defined and related to the whole. Topic sentences in division essay body paragraphs should clearly define the part as it functions in the whole.

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