In biology, there are seven levels of classification for organisms: Kingdom, Phylum, Class, Family, Genus, and Species. The next three levels are much smaller and are called subgroups. Below these levels are domains and families. The smallest classification groups, species and genera, are below them. So, which is the smallest classification group? The simplest answer is kingdom.
There are many ways to classify living things, and a good place to start is by looking at animal kingdoms. Subgroups further break down kingdoms. In addition, each kingdom is further divided into species. This means that there is more commonality between groups within a domain than there is between groups of similar organisms. For example, the Order Artiodactyla includes mammals from the kingdom Arthropoda, while the Order Cetacea includes dolphins and whales.
The next level of classification is phylum. It seeks to identify physical similarities between organisms. These similarities suggest a common ancestor. Classes are further divided by characteristics, and the next level after that is called order. In biology, classes are a subgroup of orders, and orders are a subclass of a class. A subspecies is another subdivision of a species.
Species are the lowest classification level and are the most restrictive. The most common characteristic that separates organisms in a given species is its ability to breed with other organisms in the same species. Species also determine the second part of the organism’s name. However, species classifications have a very complex history, and the classifications of organisms may have no meaningful relationship.
After species, there are genus and family. The genus name must be followed by the species names. One or more closely related genera make up a family name. Each genus and each family have significant differences in their reproductive or vegetative characteristics. This makes them distinguishable from one another. Higher ranks are distinguished based on a combination of related characters. These are just a few examples of classification in biology.