Question

Which is the smallest unit of classification of organisms?
A. Genus
B. Species
C. Family
D. Order

Answer 1

Hint: Species constitute a natural population of individuals or group of populations which resemble one another in all morphological and reproductive characters with common ancestry that can interbreed freely to produce fertile offspring. Species is the smallest unit in the hierarchical system of classification.

Complete answer:
The classification of organisms in a specific sequence of categories either in an ascending order (starting from species and reaching up to kingdom) or a descending order (from kingdom to species) is called a hierarchy of categories or Linnaean hierarchy. The hierarchy includes seven main obligate categories namely, kingdom, division or phylum, class, order, family, genus and species. The smallest unit of this hierarchical categorisation is species while the largest unit is kingdom.

Among the given options:
> Genus is a group or assemblage of related species which resemble one another in certain common features or correlated characters. All the species belong to the same genus are believed to have evolved from a common ancestor.
> Family is considered as the taxonomic category which comprises one or more correlated genera. All the genera of a family have some correlated features. They are distinguishable from genera of a family by important and characteristic differences in both vegetative and reproductive features.
> Order includes one or more related families. The category of order and higher ranks are differentiated on the basis of aggregate of related characters.

So, the answer is option B.

Note: A species is a group of organisms that share a genetic heritage, are able to interbreed, and produce offspring that are also fertile. It is one of the most specific classification that scientists use to describe animals.