Phylum
A taxonomic rank below kingdom and above class.
A phylum (plural: phyla) is a taxonomic rank in biological classification, situated below kingdom and above class. In botany, the equivalent term 'division' has traditionally been used, though the International Code of Nomenclature for algae, fungi, and plants now accepts both as interchangeable. Phyla serve as a fundamental level for grouping organisms based on shared morphological, developmental, or evolutionary characteristics, though definitions and boundaries remain subject to ongoing research and debate.
- coined_by
- Ernst Haeckel
- etymology
- Greek phylon (φῦλον, 'race, stock')
- botanical_equivalent
- division
- animal_phyla_estimated
- about 32
- plant_phyla_estimated
- about 14
- fungus_phyla_estimated
- about 8
Lore & Background
Haeckel's definition emphasized evolutionary descent, though earlier classification systems, such as those of Linnaeus and Georges Cuvier, had used different groupings. In plant taxonomy, August W.
Reader's Guide
The phylum rank is central to biological classification, but its definition has evolved and remains contested. Two primary approaches exist: a phenetic definition based on morphological or developmental similarity, and a phylogenetic definition based on evolutionary relatedness. The phylogenetic approach is considered more objective, yet it is complicated by incomplete knowledge of relationships, leading to frequent revisions—such as the merging of the phylum Pogonophora into Annelida after molecular studies, or the splitting of Mesozoa into Orthonectida and Rhombozoa. Some biologists have proposed abandoning formal phylum ranks in favor of clade-based classification. Paleontologists Graham Budd and Sören Jensen have advocated a body-plan definition, focusing on shared characters among living representatives, which aids fossil classification but introduces subjectivity. The number of recognized phyla varies widely across kingdoms: Animalia has about 32, Plantae about 14, and Fungi about 8, though these figures are estimates and subject to change with new research.
Did You Know?
- In botany, the term 'division' is traditionally used instead of phylum, though they are now considered equivalent.
- The phylum Pogonophora (bearded worms) was merged into Annelida after molecular studies revealed their close relationship.
- The number of animal phyla is estimated at about 32, but figures vary due to differing definitions and undiscovered species.
Frequently Asked Questions
What exactly is a Phylum in taxonomy?
A phylum is a major taxonomic rank used to bundle together organisms that share broad morphological, developmental, or evolutionary traits. It sits one level below kingdom and one level above class in the standard hierarchy.
Where does Phylum fit in the taxonomic ladder?
It occupies the slot directly beneath kingdom and directly above class. In practice, it acts as the broad 'family of families' that organizes the diversity within a kingdom into a manageable number of major lineages.
What's the botanical equivalent of Phylum?
Botanists have traditionally called this same rank a 'division,' though modern nomenclature codes now treat 'phylum' and 'division' as fully interchangeable terms. The underlying grouping logic remains identical regardless of which label you use.
How many phyla are there across the tree of life?
Current estimates place the number of animal phyla at roughly 32 and plant phyla at around 14. Those figures are still debated, since new phylogenetic evidence can shift boundaries or reveal previously unrecognized lineages.
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