question_answer 10)

How is a key helpful in the identification and classification of an organism?

Answer:

Key is a device (scheme) of diagnostic alternate (contrasting) characters, which provide an easy means for the identification of unknown organism. The keys are taxonomic literature based on the contrasting characters generally a pair called couplet. Each statement in the key is called a lead. Separate taxonomic keys are required for each taxonomic category such as family, genus and species for identification purposes. Being analytical in nature, two types of keys are commonly used—indented key and bracketed key. (i) Indented key provides sequence of choice between two or more statements of characters of species. The user has to make correct choice for identification. (ii) Bracketed key (1) are used for contrasting characters like indented key but they are not repeated by intervening sub-dividing character and each character is given a number in brackets.  

Indented Key		Bracketed Key
1              External ears present 2              Wings present...... Bat 2              Wings absent...... Cat 1              External ears absent......... 2              Wings present...... Bird 2              Wings absent 3              Limbs present...... Frog	(1) (1) (2) (2) (3) (3) (4)	External ears present...... (2) External ears absent...... (3) Wings present ......Bat Wings absent...... Cat Wings present...... Bird Wings absent...... (4) Limbs present...... Frog'
Indented Key		Bracketed Key
3              Limbs absent 4              Gills present...... Fish 5              Gills absent...... Snake	(4) (5) (5)	Limbs absent...... (5) Gills present...... Fish Gills absent...... Snake