Rules of Classification

The basic rules of classification are as follows:

1. A single principle or set of principles should be used consistently so that the categories (species) are mutually exclusive and jointly exhaustive.
2. The principles used should be essential.

Let us examine each of these.


Comprehension Questions

1 Identify which rule the following classification most clearly violates.

Biologists use three kinds of microscopes. The simple microscope uses a single lens. A compound microscope uses two lenses, and a stereomicroscope is used to study the external structure of specimens.

a) doesn't employ a consistent principle
b) the species of the classification are not mutually exclusive
c) the species of the classification taken together do not jointly exhaust all the objects in the genus
d) the classification doesn't use essential traits in its basis
2 Identify which rule the following classification most clearly violates.

There are many organic compounds. However, there are three types that are important to living organisms--lipids, nucleic acids, and proteins.

a) doesn't employ a consistent principle
b) the species of the classification are not mutually exclusive
c) the species of the classification taken together do not jointly exhaust all the objects in the genus
d) the classification doesn't use essential traits in its basis
3 Identify which rule the following classification most clearly violates.

Within living organism, there are proteins and then there are enzymes that serve to facilitate the biochemical reactions taking place within the organism.

a) doesn't employ a consistent principle
b) the species of the classification are not mutually exclusive
c) the species of the classification taken together do not jointly exhaust all the objects in the genus
d) the classification doesn't use essential traits in its basis
4 Identify which rule the following classification most clearly violates.

According to Aristotle, animals fell into three distinct groups--air-dwellers, land-dwellers, and water-dwellers.

a) doesn't employ a consistent principle
b) the species of the classification are not mutually exclusive
c) the species of the classification taken together do not jointly
d) the classification doesn't use essential traits in its basis


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