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