Phylum vs Class
Biological classification or scientific classification of living beings is the grouping of animals according to morphological (external), molecular, and chemical similarities found in them. In this classification, there are eight major taxonomical ranks (levels) defined for an animal, plant, or a microbe; Domain, Kingdom, Phylum, Class, Order, Family, Genus and Species. This is a hierarchical classification system where all the living beings are classified into species which has all the above eight Taxonomical Ranks according to well recognized rules and regulations (ex – International Code for Botanical Nomenclature – ICBN, for naming of plants) by international bodies. Ranking varies from Domain (the largest rank) from species (the smallest rank); Phylum and Class lie in between Domain and Species.
An example for a classification – Asian elephant (Elephas maximus),
Domain – Eukaria
Kingdom – Animalia
Phylum – Chordata
Class – Mammalia
Order – Proboscidea
Family – Elephantidae
Genus – Elephas
Species – Elephas maximus
Phylum (plural – Phyla) is the third highest taxonomical rank located in between Kingdom (higher to phylum) and Class (or in some cases Sub-phylum). There are about 86 phyla (35 animal phyla, 11 plant phyla, 6 fungi phyla, 29 bacteria phyla and 5 archaeal phyla) described. Generally phylum is referred in animal classification systems, whereas Division (similar rank to phylum) is found in plant and fungi classification instead of phylum. Division (phylum) Angiospermae (flowering plants) is the largest phylum of all and Phylum Arthropoda is the largest group for animal in which about 75% of all animal species are found.
Class is generally known as the 4th highest taxonomical rank (if we consider sub-phylum and super class the rank would be sixth) in between phylum (higher to class) and order (sometimes sub-class, infra class or super order). Ex – Class Insecta comprised of about 1.8 million species (that is about 20% of all living species in the world in a single class).
What is the difference between Phylum and Class?
• Phylum is at a higher rank than class.
• Number of species in a phylum is much higher than that in a class.
• Class is more specific than phylum.
• The probability of describing a new phylum is lower than class.
• Phylum is ranked between kingdom and class, whereas class is ranked between phylum and order.
• If a class is known, phylum can be determined, but the reciprocal can’t be done.
• Phylum of any new living being can be easily found in the field with very little knowledge; however, determining the class of a newly found living being is harder.
• Number of classes described is larger than the number of phyla described.
• Number of extinct classes is larger than the number of extinct phyla.
• Extinction probability of a class is higher than phylum.