Know Scientific Classification for the ASVAB

By Rod Powers

A long time ago, scientists looked at the world, noticed the hundreds of thousands of plants and animals around them, and decided that all these organisms (living things) needed to be labeled and grouped. To effectively study and discuss plants, animals, and other living creatures, all scientists needed to use the same names. Thus, a system of scientific classification was developed.

The most common classification system was created by Swedish botanist Carl Linnaeus, who published ten editions of his works from 1753 to 1758. Scientists often refer to this system as taxonomy. Not only does taxonomy provide official names for every plant and animal, but it also helps scientists understand how living creatures are related to one another. Modern-day taxonomy has its roots in the Linnaean taxonomic system.

No one is privy to the actual questions asked on the ASVAB (test materials are considered “controlled items” and are locked up in safes when not in use). In this category, questions can range anywhere from “How many kingdoms are there?” to “What’s the genus for Canis familiaris?”

Counting down the classification system

The scientific classification system notes the relationships and similarities among organisms. It consists of seven main levels:

  • Kingdom: A kingdom is the broadest level, so it contains the most kinds of organisms. The relationship between organisms in a kingdom is extremely loose, so members share only a few key characteristics.

  • Phylum: Phylum (plural phyla) is the next major taxonomic group. Within the kingdoms, organisms are divided into phyla by general characteristics. For example, in the Animal kingdom, animals with backbones (vertebrates) are placed in a separate phylum from animals without backbones.

  • Class: Organisms in a phylum are divided into classes. In the Animal kingdom, for example, birds, mammals, and fish all go in their own classes. Among plants, all flowering plants comprise the Angiosperm class, and all conifers, such as pines and spruces, comprise the Conifer class.

  • Order: Scientific groupings don’t follow hard and fast rules, so when you get to the order of a living thing, there’s disagreement about where it belongs. You may find that different scientific organizations group creatures in different orders or families.

  • Family: Families further divide organisms of the same class by similar characteristics. Sometimes not all scientific organizations agree about the exact family an organism should be classified in.

  • Genus: Two or more species that share unique body structures or other characteristics are closely related enough to be placed in a single genus. A genus may include only a single species if no other organism has characteristics similar enough for it to be considered the same genus.

  • Species: A species is the most specific level, so it contains the fewest types of organisms. Organisms of the same species have very similar characteristics.

To get a better idea of how the scientific classification system works, consider how a lion is classified:

  • Kingdom Animalia: This kingdom includes all animals.

  • Phylum Chordata: All vertebrate animals belong to the phylum Chordata.

  • Class Mammalia: All mammals belong to this class.

  • Order Carnivora: All mammals that eat meat belong to the order Carnivora.

  • Family Felidae: The family Felidae includes all cats.

  • Genus Panthera: This genus includes all the roaring cats, such as lions, tigers, jaguars, and leopards.

  • Species leo: This is just a lion.

Humans belong to the kingdom Animalia, the phylum Chordata, the class Mammalia, the order Primata, the family Hominidae, the genus Homo, and the species sapiens. You know, just in case you were wondering.

Visiting the kingdoms

Not every scientist agrees (scientists rarely agree on any subject), but in general, most lab-coated individuals settle on five as the number of kingdoms. Check out the kinds of organisms that comprise the five kingdoms:

  • Animals: This is one of the two largest kingdoms, and it includes many-celled organisms that, unlike plants, don’t have cell walls, chlorophyll, or the capacity to use light to make energy (photosynthesis). Members of this kingdom can move. The Animal kingdom includes more than one million species.

  • Plants: Plants are also one of the two largest kingdoms. This kingdom includes organisms that can’t move, don’t have obvious nervous or sensory systems (the Venus flytrap is one exception), and possess cell walls made of cellulose. More than 250,000 species belong to the Plant kingdom.

  • Monerans: This kingdom includes bacteria and cyanobacteria (blue-green algae) — one-celled organisms that don’t have a nucleus. More than 10,000 species have been discovered and classified in the Monera kingdom.

  • Protists: Protists include one-celled organisms that do have a nucleus, such as the protozoan, which you may remember from biology class. This kingdom consists of more than 250,000 species.

  • Fungi: Examples of common fungi are mushrooms and yeast. Fungi don’t photosynthesize (use light to create energy) like plants, but they do have cell walls made of a carbohydrate called chitin. More than 100,000 species belong to the Fungi kingdom.

Thirty-three phyla make up the Animal kingdom, and 12 main phyla comprise the Plant kingdom. Monerans consist of two phyla; protists have seven phyla; and fungi are made up of four phyla. Numerous classes, orders, families, genera, and species fall under each phylum.

Just name it: Showing off your genius about the species

Each organism is given a scientific name that consists of two words (usually derived from Latin) — the genus and the species of the organism. The genus is the first word, and the species is the second. Thus, Homo sapiens refers to humans. Canis familiaris is the family dog, and Canis lupus is the family wolf. Because wolves and dogs share many similarities, they share the same genus (no, no, not the same genes, the same genus).

When writing a scientific name, the genus name is capitalized, and the species name is all lowercase. Both names are italicized.