Mada za sehemu hiiPrinciples Of ClassificationMada 5
Taxonomic hierarchy refers to the sequential arrangement of the taxonomic group in definite order from higher to lower categories.
In classification organisms are put into groups, categories or ranks based on their similarities and differences. The main objective of taxonomy is to put organisms in different groups which show their evolutionary relationship.
The ranks or categories used in classification are known as taxa (in plural) (singular taxon).
The taxa or taxonomic groups are arranged in hierarchical order i.e. from the largest group to the smallest group (descending sequence).
The taxonomic hierarchy consists of seven main categories or taxa. These are the kingdom, phylum, class, order, family, genus and species. In plants however the division is used in categories in place of phylum while remaining categories are the same.
Linnaeus was the first taxonomist to establish a definite hierarchy of taxonomic ranks.
The figure below is an example of taxa or hierarchy of taxonomic ranks.
Lesson Explainer: Taxonomic Hierarchy
- Universal: The taxonomic system is used globally to classify and categorize organisms.
- Hierarchical: Organisms are arranged in a ranked structure, starting from broad categories to more specific ones.
- Inclusiveness: Each rank includes all organisms that share certain characteristics and can be further subdivided.
- Definitive Rank: Each level or rank in the hierarchy (e.g., Kingdom, Phylum, Class, Order) is clearly defined.
- Binomial Nomenclature: Each species is given a unique two-part scientific name (genus + species) for universal identification.
- Sequential Arrangement: Organisms are classified in a sequential manner, from the most general to the most specific level.
- Stability: The taxonomic ranks are fixed and stable for classification purposes, though updates may occur with new discoveries.
- Flexibility: Taxonomy can be adapted and revised as new data and research on organisms become available.
The kingdom
This is the highest taxonomic category, it includes all organism that share a set of distinguishing common characters.
The phylum / Division
The term phylum is used for animals and division for plants.
The phylum consists of closely related classes. A phylum can have one or more classes.
Class
Class is a group of closely related orders. For example class dicotyledonae of flowering plants include all dicots which are grouped into several orders such as Rosales, passiflorales, polemoniales etc.
Order
Consists of a group of closely related family.
Family
Family is a group of closely related genus.
Genus
Genus is a group of closely related species.
Species
Species is the lowest rank of classification. A species refers to a group of organisms which are similar and can freely interbreed to produce fertile offspring. This means that the species is reproductively isolated from other species.
Fertile means capable of having offspring i.e. members of the same species can, if left alone in their natural environment, mate with one another to produce offspring which in turn, are also able to produce offspring.
Exception of the species definition
If a male tiger mates with a female lion and produces an offspring which is fertile (can reproduce).
Male lion and female tiger produce offspring (the liger) which is infertile.
Male donkey and female horse produce infertile offspring (the mule).
Species - Felis catus
| Category | Taxonomic Rank |
|---|---|
| Kingdom | Animalia |
| Phylum | Chordata |
| Class | Mammalia |
| Order | Primates |
| Family | Hominidae |
| Genus | Homo |
| Species | sapiens |
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