Key is a 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.
Key are analytical in nature and help to identify the differences between species and identify new species.
Try to collect all the currently accepted meanings for the word ‘species’. Discuss
with your teacher the meaning of species in case of higher plants and animals on one hand, and bacteria on the other hand.
Species is the basic unit of taxonomy. It can be defined as a group of individual organisms capable of interbreeding freely among themselves under natural conditions to produce fertile offsprings. Therefore, a group of similar individuals that are reproductively isolated from the other group of individuals form species. Species can also be defined as a group of individuals that share the same gene pool.
Illustrate the taxonomical hierarchy with suitable examples of a plant and an
animal.Taxonomic hierarchy is the arrangement of various taxa in a hierarchical order. In the hierarchy, species is present at the lowest level whereas kingdom is present at the highest level.
A Taxonomic hierarchy
Classification of a plant
As an example, let us classify Magnifera indica (Mango).
Kingdom – Plantae
Division – Angiospermae
Class – Dicotyledonae
Order – Sapindales
Family – Anacardiaceae
Genus – Magnifera
Species – indica
Classification of an animal
As an example, classification MAN
Kingdom – Animalia
Phylum – Chordata
Class – Mammalia
Order – Primata
Family – Hominidae
Genus – Homo
Species – Sapiens
Taxa is the scientific term for each unit or category of classification. It indicates categories at different levels.
For example, the basic level of classification is species, followed by genus, family, order, class, phylum or division, in ascending order. The highest level of classification is known as the kingdom. So, each of these categories can be called as a taxon.
Order
Phylum
Kingdom
Species
Order
Kingdom
Genus
Order
Phylum
Both (a) and (c) represent correct sequences of taxonomic categories as the correct hierarchical arrangement of taxonomic categories in ascending order is
Species → Genus → Family → Order → Class → Phylum → Kingdom
In sequence (b), species should have been followed by genus.
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