There are millions of known organisms and many more yet to be identified. Classification groups organisms on the basis of similarities and differences, making identification, naming, comparison and study of evolutionary relationships easier.
Living organisms are classified to make the study of their vast diversity systematic, convenient and meaningful.
As biological knowledge grows, taxonomists use additional evidence from morphology, anatomy, cell structure, development, ecology and molecular data. These newer data can change the placement of organisms and improve older classification systems.
Classification systems change because new organisms, new characters and new evolutionary relationships are continually discovered.
Classification depends on the purpose of grouping. For example, in a classroom one may group people by age or class; in a workplace by occupation; in a locality by language or residence. The chosen criteria should be clear and consistently applicable.
People can be classified by observable or useful criteria such as age, sex, occupation, language, place of residence, habits or relationship.
Correct identification links an organism to known information about its morphology, relationships, distribution, uses and ecological role. For populations, it helps compare similarities and differences within and between groups of organisms.
Identification tells us the correct name, characters and taxonomic position of an organism or population.
- A. Mangifera Indica
- B. Mangifera indica
In binomial nomenclature, the genus name begins with a capital letter and the specific epithet begins with a small letter. Therefore, Mangifera indica is correct, while Mangifera Indica is not.
Mangifera indica is correctly written.
Taxa may occur at different levels, such as species, genus, family, order, class, phylum/division and kingdom. Examples include Homo sapiens as a species, Homo as a genus, Hominidae as a family, Mammalia as a class and Animalia as a kingdom.
A taxon is a unit of classification representing a rank or category in the taxonomic hierarchy.
- a. Species Order Phylum Kingdom
- b. Genus Species Order Kingdom
- c. Species Genus Order Phylum
The full ascending hierarchy is species, genus, family, order, class, phylum/division and kingdom. Option (c) preserves this relative order for the listed categories.
(c) Species Genus Order Phylum is the correct sequence among the given choices.
Phylum is a high animal category containing related classes; in plants the comparable category is division. Class contains related orders. Order is an assemblage of related families. Family contains related genera and is characterised by shared features. Genus contains closely related species with more common characters than species belonging to other genera.
Phylum, class, order, family and genus are taxonomic categories at different levels of hierarchy.
Mango: species Mangifera indica; genus Mangifera; family Anacardiaceae; order Sapindales; class Dicotyledonae; division Angiospermae; kingdom Plantae. Human: species Homo sapiens; genus Homo; family Hominidae; order Primata; class Mammalia; phylum Chordata; kingdom Animalia.
Example plant: mango. Example animal: human.