From the simple jellyfish to the more complex primate, the animal kingdom is home to a huge variety of organisms. It is estimated that there are 9-10 million different animal species on Earth. To catalog such a wide range of unique specimens, biologists use a classification system that provides pyramid "categories", in which living beings are grouped according to the characteristics they have in common. With practice, you will have no problem following this system!
Steps
Part 1 of 3: Understanding the Taxonomic Table
| Rank | Description | Examples |
|---|---|---|
| Kingdom | The largest of the traditional taxonomic categories. It divides living things into large groups that contain many species. | Animalia, Plantae, Bacteria |
| Phylum | Large groups that divide the members of a kingdom into categories, based on some broad structural and genetic characteristics. | Chordata, Magnoliophyta, Proteobacteria |
| Class | Mid-level groups that further subdivide the members of a phylum into more specific categories, based on morphological characteristics, evolution, etc. | Mammalia, Magnoliopsida, Gamma Proteobacteria |
| Order | A group that divides the members of a class into categories of species that share typical and well-defined characteristics, as well as having common ancestors. The general name of a group of animals often comes from its order. For example, members of Primates are often collectively referred to as apes. | Primates, Rosales, Enterobacteriales |
| Family | Rather specific group that divides the members of an order into logical and recognizable categories of related organisms. Family names often end in "ae". | Hominidae, Rosaceae, Enterobacteriaceae |
| Type | Together that divides the members of a family into compact categories of organisms that are very similar to each other. Almost all members of a genus are direct descendants of a single common ancestor. The genus name forms the first part of the scientific name of an organism and is always written in italics. | Homo, Rubus, Escherichia |
| Species | The narrowest classification. The species name refers to a specific and exact group of organisms, basically identical in terms of morphology. Only members of the same species can reproduce and have fertile descendants. Species names form the second part of an organism's scientific name and are always written in italics. | sapiens, rosifolius, coli |
Step 1. Learn about the taxonomic classification system used to identify animals
This system, based on the characteristics of living things, was first adopted by the eighteenth-century botanist Carl Linnaeus. In general, however, when biologists speak of taxonomic categories, they refer to the seven main groups, listed in the previous table, from the largest to the smallest. Note that the entries in the "Examples" column have different colors to indicate the taxonomic "path" of three organisms.
- The items in red follow the path of Homo sapiens or man (an animal).
- The entries in blue offer the example of Rubus rosifolius, the bramble (a plant).
- Entries in green identify Escherichia coli, a well-known bacterium.
Step 2. Memorize the phrase "D do with the organ I make big blasts" to remember the taxonomic units
Many mnemonic tools are useful for remembering the seven main taxonomic categories (kingdom, phylum, class, order, family, genus and species) and their order. The first letter of each word of the sentence corresponds to the first letter (or sound in the case of a phylum) of a taxonomic group, in the correct order. In other words, "Re" corresponds to "kingdom", "fa" corresponds to "phylum" and so on.
Step 3. When trying to classify an animal, start with the largest group and work your way up to the smallest
For example, each animal falls under the Animalia Kingdom, but only a single species has the name sapiens. As you progress from kingdom to species, the animal you want to classify will have to meet more and more requirements to fall into a given category.
Step 4. Classify an animal based on its morphology
The most important step in recognizing an animal's species is identifying its morphology. This term refers to the internal and external characteristics of the organism. For example, does it have fur or scales? What kind of abdomen does he have? By knowing the characteristics of the animal you want to classify, you will be able to do it correctly.
Part 2 of 3: Assigning a Taxonomic Classification
Step 1. Begin with the Animalia Kingdom
All animals, by definition, belong to the Animalia kingdom (also known as "Metazoa"). All organisms that fall into this kingdom are animals and all those that are not part of it are not. Consequently, to classify an animal, you will always have to start from this broad general category.
- In addition to animals, the other taxonomic kingdoms include Plantae (plants), Fungi (fungi), Protista (unicellular eukaryotes), and Monera (prokaryotes).
- As an example, let's try to classify modern man according to the rules of taxonomy. Humans are living animals that breathe, so we're going to start with the kingdom Animalia, as said previously.
Step 2. Assign a phylum to your pet
The phylum (plural: phyla) is the group that directly follows the broad category of the Animalia Kingdom, which contains 35 different phyla. In very general terms, each phylum groups its members according to the general morphology. For example, organisms in the phylum Chordata all have a rigid rod-like structure, which runs along the body (like the spine), with a hollow dorsal nerve cord above it and a belly below it. In contrast, members of the phylum Echinodermata have a five-pointed radial symmetry and the characteristic spiny skin.
- It is important to note that taxonomic categories were created before the advent of modern genetic technologies. As a result, inconsistencies emerged between the grouping of some species in a phylum and their real genetic affinity. This has led to further distinctions within phyla, such as that between platyhelminths (flat worms) and animals with digestive tracts running throughout the body.
- In our example we classify humans in the phlyum Chordata because we have a hollow dorsal nerve cord above the spine.
Step 3. Assign a class to your pet
Class is the next stage of classification. There are 111 different classes that belong to the phyla of the animal kingdom. Usually, the organisms of a class are grouped on the basis of their genetic and morphological similarities. Below you will find some examples of classes belonging to the phylum Chordata:
- Mammalia (mammals): warm-blooded animals, with hair, four atria heart and mammary glands capable of secreting milk. Usually (but not always), they give birth to live puppies.
- Aves (birds): warm-blooded, egg-laying animals with a four-atria heart, feathers and wings.
- Reptilia (reptiles): cold-blooded, egg-laying, scaly or scaly animals (usually) three-atria hearts.
- Amphibia (amphibians): cold-blooded animals, with three-atria hearts, (usually) a water-bound larval life cycle, water-permeable eggs, and skin that acts as a respiratory organ.
-
Furthermore, within the phylum Chordata, there are numerous classes that describe fish and organisms of a similar nature. The fish are:
- Osteichthyes (Osteichthyes): bony fish (ray-finned or fleshy)
- Chondrichthyes (Chondrichthyes): cartilaginous fish (sharks, catfish and rays)
- Agnatha (Agnati): fish without jaws and jaws (lamprey and hagfish).
- In our example, humans fit into the class Mammals, because they have the qualities listed above.
Step 4. Place an order for your pet
Orders are used to group animals into easier-to-manage units, more specific than phyla and class, but less particular about genera and species. For example, the two orders of the Reptiles class are:
- Testudines: turtles, tortoises, etcetera;
- Squamata: snakes and lizards;
- In our example, humans fit the order Primates, along with apes and our extinct proto-human ancestors.
Step 5. Assign your pet to a family
After the order, the taxonomic classification of an organism begins to become quite specific. For example, the common name of animals often comes from the Latin root of its family name; geckos (which belong to the Gekkonidae family) got their name in this way. Some examples of families within the Squamata order are:
- Chamaeleonidae - chameleon
- Iguanidae - iguana
- Scincidae - skink
- In our example, humans are part of the family Hominidae along with the great apes and early proto-humans.
Step 6. Assign your pet to a gender
The genus is used to distinguish a group of organisms from other specimens that are apparently similar or even share the same name. For example, all members of the Gekkonidae family are geckos, but those belonging to the genus Dixonius (leaf-toed geckos) are different from those of the genus Lepidodactylus (scale-toed geckos) and the same is true for the other 51 genera of the Gekkonidae family.
In our example, men fall into the gender Homo, which includes modern man and our best known ancestors (neanderthal man, cro-magnon man, and so on).
Step 7. Assign your pet to a species
Usually the species of an organism is the most specific taxonomic rank that can be attributed to it. Species are often defined as groups of similar-looking specimens that are able to reproduce with each other and are unable to reproduce with members of other species. In other words, only animals belonging to the same species can successfully reproduce. In some cases, organisms of different species can procreate, but the descendants are almost always sterile and cannot produce offspring (a common example is the mule, which is unable to reproduce and is obtained by crossing a horse and a donkey.).
- It is important to note that some animals belonging to the same species can be very different, despite their degree of correlation. For example, a Chihuahua and a Great Dane are quite different, but they are both dogs.
- In our example, we will finally attribute the species to man sapiens. This category excludes all forms of life other than man. Note that modern humans, of the genus Homo and of the sapiens species, can have a great variety of morphological differences: size, facial appearance, skin color, hair color, and so on. Nonetheless, any healthy couple consisting of a man and a woman can produce fertile children, so all people are homo sapiens.
Step 8. If necessary, assign your pet to a subspecies
As a general rule, an animal's species is the most specific classification it can receive. There are, however, many exceptions, according to which scientists further subdivide specimens of one species into two or more subspecies. A given species cannot have a single subspecies; there will always be at least two or none. Commonly, subspecies are assigned when, within a species, certain groups of organisms are able to reproduce but fail to reproduce due to geographic distances, behavioral patterns, or other reasons.
In our example, if we wanted to refer to the humans inhabiting the Earth today, we could use the subspecies sapiens, to further differentiate them from Homo sapiens idaltu, another type of proto-human belonging to the same species.
Part 3 of 3: Classifying an Animal Based on its Scientific Name
Step 1. Start with an animal's scientific name
The two most specific taxonomic classifications, the genus and the species, are used to give the scientific name to each organism. In other words, the official name of an animal, recognized by scientists around the world, is its Genus (uppercase) followed by its species (lowercase). For example, the scientific name of modern man is Homo sapiens, because it belongs to the genus Homo and the species sapiens. Note that the scientific names of living things are always written in italics.
- Since the genus and species of an animal are the most specific taxonomic classifications, this information is often sufficient to identify an organism.
- If you don't know the scientific name of the animal you want to classify, try searching the internet. Search for the animal's common name (eg "dog") along with "scientific name". This way, you will be able to find the information you are looking for right away.
Step 2. Use an animal's scientific name as a starting point for a search
Since the scientific name is made up of genus and species, you can use it as a starting point to trace the rest of the information on the taxonomic classification of the specimen.
Step 3. Work back through all groups in a deductive process
If you know the scientific name of an animal, it is possible to determine its taxonomic classification thanks to the deduction, using the morphology of the species, its evolutionary history and genetic relationships with other specimens, to trace the family, order and so on. Use the information you know about the species to make it easier to find. If possible, check the accuracy of your conclusions in a biology textbook.
- For example, in the example of Homo sapiens, if we know that humans share a recent evolutionary ancestor with great apes, we can place them in the Hominidae family along with the other great apes (chimpanzees, gorillas and orangutans). Since the great apes are primates, we can place Homo sapiens in the order Primates. From here, getting to the class and the phylum is simple. Of course, all primates are mammals, so we can say that humans belong to the Mammals class and all mammals have a spinal column, so we can say that humans belong to the phylum Chordata.
- As mentioned at the beginning of this article, all animals belong to the Animalia kingdom regardless of their taxonomic classification.
