Give an account of different kinds of taxonomy with their merits and demerits
Answers
Meaning of Taxonomic Key:
A key is a device, which when properly constructed and used, enables a user to identify an organism. Keys are devices consisting of a series of contrasting or contradictory statements or propositions requiring the identifier to make comparisons and decisions based on statements in the key as related to the material to be identified.
Thus, a taxonomic key is a device for quickly and easily identifying to which species an unknown plant belongs.
The key consists of a series of choices, based on observed features of the plant specimen. It provides a choice between two contradictory statements resulting in the acceptance of one and the rejection of the other.
A single pair of contradictory statements is called a couplet and each statement of a couplet is termed a lead. By making the correct choice at each level of the key, one can eventually arrive at the name of the unknown plant.
Suggestions for the Use of Taxonomic Keys:
(a) Appropriate keys should be selected for the materials to be identified. The keys may be in a flora, manual, guide handbook, monograph, or revision. If the locality of an unknown plant is known, a flora, guide, or manual treating the plants of that geographic area may be selected.
If the family or genus is recognized, one may choose to use a monograph or revision. However, if the locality is unknown a general work may be selected. If materials to be identified are cultivated, one of the manuals treating such plants should be selected, since most floras do not include cultivated plants unless naturalized.
b) The introductory comments on format details, abbreviations, etc. should be read before using the key.
(c) Both the leads of a couplet should be read before making a choice. Even though the first lead may seem to describe the unknown material, the second lead may be even more appropriate.
(d) A glossary should be used to check the meaning of terms, which one does not understand.
(e) Several similar structures should be measured, when measurements are used in the key, e.g. several leaves and not a single leaf should be measured. No decision should be made on a single observation. Rather it is often desirable to examine several specimens.
(f) The results should be verified by reading a description, comparing the specimen with an illustration or an authentically named herbarium specimen.
Suggestion for Construction of Taxonomic Keys:
(a) Constant characteristics rather than variable ones should be used.
(b) Proper measurements rather than terms like “large” and “small” should be used.
(c) Characteristics that are generally available to the user of the key rather than seasonal characteristics or those seen only in the field should be used.
(d) A positive choice should be made. The term “is” instead of “is not” should be used.