Question

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

Answer 1

‘Key is an artificial analytic device having a list of statements with dichotomic table of alternate characteristics. Taxonomic
keys are aids for rapid identification of unknown plants and animals based on
the similarities and dissimilarities. Keys are primarily based on stable and reliable characters. The keys are helpful in a faster preliminary identification which can bebacked up by confirmation through comparison with detailed description of the taxon provisionally identified with. Separate taxonomic keys are used for each taxonomic category like Family, Genus and Species.

Answer 2

Key is another taxonomical aid that helps in identification of plant and animal species. These keys are based on similarities and dissimilarities in characters, generally in a pair called couplet.

Each statement in a taxonomic key is referred to as a lead. For categorizing each taxonomic rank, such as family, genus, species, etc., different keys are used. It is also useful in identification of unknown organisms.

Keys are of two types- indented and bracketed keys. Indented key provides a sequence of choices between two or more statements while in bracketed key, a pair of contrasting characters are used.

(i) Indented key to identify different species of Rhododendron.

1. Leaves evergreen

2. leaves densely hairy below, orange or white hair; flower

appears to have separate petals

………………………. Rhododendron groenlandicum

2. hair absent on leaves, flower has five petals fused in a shallow

tube

………………………. Rhododendron maximus

1. Leaves deciduous

3. pink flowers with two free petals and three fused petals

………………………. Rhododendron canadense

3. white to pink flowers with all petals fused together

(ii) Bracketed key to identify different species of Rhododendron.

1. Leaves evergreen-----------------------------------------------2

1. Leaves deciduous-----------------------------------------------3

2. Leaves densely hairy below, orange or white hair; flower

appears to have separate petals

……….………………………. Rhododendron groenlandicum

2. Hair absent on leaves, flower has five petals fused in shallow

tube

………………………………..Rhododendron maximus

3. Pink flowers with two free petals and three fused petals

……………………………… Rhododendron canadense

3. White to pink flowers with all petals fused together-----4