Revision: Diversity of Living Organisms >> The Living World Biology (Theory) ISC (Science) ISC Class 11 CISCE

A taxon is a taxonomic group at any level. It represents a group of organisms at any level.

Classes comprising animals like fish, amphibians, reptiles, birds, and mammals constitute the next higher category called phylum. All these, based on common features like the presence of the notochord and dorsal hollow neural system, are included in the phylum Chordata. In the case of plants, classes with a few similar characters are assigned to a higher category called division.

Genus comprises a group of related species that have more characters in common in comparison to species of other genera. We can say that genera are aggregates of closely related species. For example, potato and brinjal are two different species, but both belong to the genus Solanum. Lions (Panthera leo), leopards (P. pardus), and tigers (P. tigris), with several common features, are all species of the genus Panthera. This genus differs from another genus, Felis, which includes cats.

1. The next category, family, has a group of related genera with a smaller number of similarities as compared to genus and species. Families are characterised on the basis of both vegetative and reproductive features of plant species.
2. Among plants, for example, three different genera, Solanum, Petunia, and Datura, are placed in the family Solanaceae. For example, the genus Panthera, comprising lions, tigers, and leopards, is put along with the genus  Felis (cats) in the family Felidae. Similarly, if you observe the features of a cat and a dog, you will find some similarities and some differences as well.
3. They are separated into two different families – Felidae and Canidae, respectively.

1. You have seen earlier that categories like species, genus, and families are based on a number of similar characters.
2. Generally, order and other higher taxonomic categories are identified based on the aggregates of characters. Order, being a higher category, is the assemblage of families that exhibit a few similar characters.
3. The similar characters are fewer in number as compared to the different genera included in a family. Plant families like Convolvulaceae, Solanaceae are included in the order Polymoniales, mainly based on their floral characters.
4. The animal order, Carnivora, includes families like Felidae and Canidae.

This category includes related orders. For example, order Primata, comprising monkeys, gorillas, and gibbons, is placed in class Mammalia, along with order Carnivora, which includes animals like tigers, cats, and dogs. Class Mammalia has other orders as well.