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

-Kumudinee, Subject Matter Expert at Edumarz.

Solution: Key is the device or scheme of diagnostic alternate (contrasting) characters.

It provides easy means or criteria and features for the identification of unknown organisms.

The key is taxonomic literature based on the contrasting characters, generally a pair called couplet.

Each and every 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 and nomenclature.

As keys are analytical in nature they can be of two types of keys commonly used—indented key and bracketed key.

(i) Indented key provides the sequence of choice between two or more statements of phenotypic characters of in species so the user can make the correct choice for identification.

(ii) Bracketed key is used for contrasting characters as indented key but they are not repeated by intervening sub-dividing characters 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