Question

Basic smallest unit of classification is ______.
a) Species
b) Family
c) Class
d) Genus

Answer 1

Hint: The smallest unit of classification is based on the alikeness of the organisms based on their morphological and reproductive characteristics due to which the organisms can breed within the same group successfully to produce a healthy offspring.

Complete answer
A species is a group of individuals who are from the same ancestors and are fertile enough to interbreed among themselves to produce fertile offspring which are alike in morphological; as well as reproductive characteristics. For example, Bos taurus and Bos indicus are two different species of cow.
A family is a broader classification of several genus which have similar characteristics with considerable differences. The species within a family can be differentiated based on several vegetative and reproductive features present in them. For example, Canidae is a family consisting of dogs, wolves and foxes.
A class is defined as a broader grouping of several Orders which have one or similar characteristics in common with considerable differences. For example, Mammalia is a class which includes all the organisms giving birth to their offspring. They are either airborne, water borne or land borne.
A Genus is a group of multiple species which have evolved from a single ancestor. The species in the same genus have several common characteristics. For example, Homo sapiens (Humans) and Homo erectus (Prehistoric Humans) belong to the same genus.

Note:
The order of classification is done in the following manner, starting from the highest to lowest: Kingdom, Phylum, Class, Order, Family, Genus and Species. In a newer method of classification, several kingdoms are grouped under one Domain, but it has not been accepted universally so far.