From the simplest jellyfish to the most complex primates, the animal kingdom contains a wide variety of organisms. It is estimated that between 9 and 10 million unique species of animals exist on Earth. To categorize such great diversity, biologists use a stratified classification system to classify animals based on their relationships. You too can master this system by learning it.
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Part 1 of 3: Understanding Taxonomy Tables
| Level | description | Example |
|---|---|---|
| Kingdom | The most extensive level of traditional taxonomy. This level divides life into broad and inclusive categories. | Animalia, Plantae, Bacteria |
| phylum | A broad classification that divides members of the royal level into specific categories based on genetic kinship and broad structure. | Chordata, Magnoliophyta, Proteobacteria |
| Class | Intermediate grouping that divides phyla members into narrower categories based on body skeleton, common evolutionary ancestry, etc. | Mammalia, Magnoliopsida, Gamma Proteobacteria |
| Order | The grouping of class members becomes narrower based on kinship, body features, and specific common ancestor. Common names for groups of animals are usually taken from their order level - e.g., members of the Primate group are generally called "apes". | Primates, Rosales, Enterobacteriales |
| Family | A grouping specific enough to divide members of an order into logically identifiable groups of related organisms. Family-level names usually end in "ae". | Hominidae, Rosaceae, Enterobacteriaceae |
| Genus | Specific groupings that divide family members into whole groups of organisms that are related to one another. Almost all members of the genus are direct descendants of a common ancestor. The genus name is written as the first name of an organism, and is always written in italics. | Gay, Rubus, Escherichia |
| Species | The most specific classification. The level of species taxonomy refers to a clear and specific group of organisms that have major similarities in morphology. Only members of the same species can produce viable and fertile offspring. The species name is the second name in an animal's scientific name, and is written in italics. | sapiens, rosifolius, coli |
Step 1. Study the taxonomic classification system used to identify animals
This system of classifying animals based on their characteristics was first compiled in the 18th century by a botanist, Carl Linneaus. However, generally, when biologists talk about taxonomic levels, they mean the seven main levels listed in the table above from the broadest to the narrowest. Note that the sample columns are written in different colors to indicate the taxonomic "paths" of the three organisms being sampled.
- Writing in red follows the taxonomic path of Homo sapiens, or humans (which includes animals).
- Writing in blue follows the taxonomic path of Rubus rosifolius, or Indian raspberry (which includes plants).
- The writing in green is an example of the taxonomic pathway of Escherichia coli, commonly known as E. coli (a bacterium).
Step 2. Use the donkey bridge "King Filip Escapes Fijians Fried Sandals" to remember taxonomic tiers
The various donkey bridges, an example of which is above, are very useful for remembering the seven main taxonomic levels, namely: kingdom, phylum, class, order, family, genus, and species, and their order. The letters or words in the donkey bridge in order according to each taxonomic level. In other words "king" refers to "kingdom", "filip" refers to "phylum", and so on.
Step 3. Classify from the broadest to the narrowest
For example, all animals can be included in the animal kingdom, but only certain animals are included in the species "sapiens". As the taxonomic level gets narrower, the animal you classify has to fulfill more and more things to be included in it.
Step 4. Classify animals based on their morphology
An important part of classifying animals is identifying their morphology. Morphology is the external and internal characteristics of an animal. For example, is the animal hairy or scaly? What type of stomach is in his body? Knowing the characteristics of the animal you are going to classify is very useful in helping you arrange them correctly.
Part 2 of 3: Determining the Taxonomic Classification
Step 1. Start from animalia kingdom
All animals belong to the kingdom animalia (sometimes also referred to as "Metazoa"). All organisms belonging to this kingdom are animals, and all organisms that do not belong to it are not animals. Thus, when classifying animals, you will always be dealing with these main categories.
- Besides animalia, the other kingdoms of organisms are Plantae (plants), Fungi (fungi), Protista (single-celled eukaryotes), and Monera (prokaryotes).
- For example, try classifying modern humans according to taxonomic classification rules. Humans are living and breathing animals, so start by classifying them into the "animalia" kingdom, according to the instructions above.
Step 2. Define the animal phylum
Phylum (plural: fila) is a taxonomic level right under the large umbrella of the animal kingdom. There are 35 phyla in the animal kingdom. Roughly speaking, each phylum is classified according to the general morphology of the animal. For example, all animals belonging to the phylum "chordates" have a strong rod structure along their body (like the spine), with a hollow spinal cord at the back and a digestive tract below. Meanwhile, all members of the phylum echinoderms have a radial pentameral symmetry body, and characteristic spiny skin.
- Be aware that taxonomic tiers were created before modern genetic technology developed. As a result, there is a genetic mismatch between organisms belonging to the same phylum. This means, certain phyla may be classified into other phyla. For example, platyhelminthes (flatworms) which have branched intestines are included in the phylum in the animal kingdom.
- In this example, we can classify humans into the phylum chordates because we have a hollow nerve cord above the spine.
Step 3. Determine the class of the animal
After the phylum, determine the class of animals. In all the phyla, there are 111 classes in total. Generally, members of a class are grouped according to their genetic or morphological relationship. The following are some examples of classes in the phylum Chordata:
- Mammalia - warm blooded, hairy, four bear heart, mammary glands to secrete milk. Usually (though not always) produce live offspring.
- Aves (birds) - warm-blooded, egg-laying, four-bear heart, feathers and wings.
- Reptiles (reptiles) - cold-blooded, egg-laying, scaled or shelled, (usually) have a triple bear heart.
- Amphibia (amphibians) - cold blooded, has a three-bear heart, and (usually) a larval life cycle in water, the eggs can be penetrated by water, and the skin that functions as a respiratory organ.
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In addition, within the phylum chordata, there are a number of classes of fish or fish-like organisms. Fish classes are:
- Osteichthyes - bony fish (spiked fish)
- Chondricthyes - cartilaginous fish (sharks, skates, and rays)
- Agnatha - jawless fish (lamprey and ghost fish)
- In the example here, we can classify humans into classes Mammals because we have the characteristics mentioned above.
Step 4. Determine the order of the animal
After class, the next taxonomic level is order. Orders are used to classify animals more specifically than phyla and class, but still more broadly than genus, species, and so on. For example, the two orders in the Reptilia class are:
- Testudine - tortoise, tortoise, etc.
- Squamata - snake and lizard
- In the example here, we can classify humans into orders Primate along with the extinct monkeys, apes and proto-humans.
Step 5. Determine the animal family
After classifying the order, the taxonomic classification of animals will become more specific. For example, the common name of a particular animal may be derived from the Latin name of the family -- for example, the gecko, which belongs to the family Gekkonidae. Some examples of other families in the order Squamata are:
- Chamaeleonidae - chameleons
- Iguanidae - iguanas
- Scincidae - skink
- In the example here, we can classify humans into families Hominidae with great apes and early proto-humans.
Step 6. Determine the genus of the animal
An animal's genus (plural: genera) is used to distinguish it from other types of animals that look similar or even share the same common name. For example, the common name for all members of the family Gekkonidae is gecko (gecko), but members of the genus Dixonius (leaf-toed gecko) differ from members of the genus Lepidodactylus (scaly-toed gecko), and so on for all 51 genera in the family Gekkonidae.
In the example here, we can classify humans into the genus Homo, which includes modern humans and early human ancestors such as - neanderthals, cro-magnons, and so on.
Step 7. Determine the animal species
Animal species is usually the most specific taxonomic level. Species is often defined as individuals with the same morphological appearance, can produce offspring with each other, and cannot produce offspring with other species. In other words, only animals of the same species can reproduce and produce live and fertile offspring. Animals that do not belong to the same species can sometimes produce offspring, but are usually sterile and cannot reproduce (an example is the mule, which cannot produce offspring and is the result of reproduction between a horse and a donkey).
- Understand that animals of the same species may have different appearances even if they are closely related. For example, the chihuahua and the great dane look quite different, even though they belong to the same species.
- In the example here, we can classify humans into species sapiens. Apart from humans, no other organisms fall into this category. Keep in mind that modern humans belonging to the genus Homo and species sapiens have a variety of morphological forms--body size, facial appearance, skin color, hair color, and so on. However, all male and female pairs can produce live and fertile offspring, so everyone is human.
Step 8. Determine the subspecies of the animal, if necessary
Generally, animal species is the most specific classification. However, there are many exceptions to the above rules, scientists further classify an animal species into two or more subspecies. A species will always have two or more subspecies, or none at all--but never just one. Subspecies is generally given if within a species there is a group of organisms that can produce fertile offspring, but this is not the case in nature because of geographical differences, behavioral patterns, or other things.
In the example here, if we refer to the anatomy of modern humans (humans living on earth today), we can use subspecies sapiens to distinguish it from Homo sapiens idaltu, another type of proto-human within the species Homo sapiens
Part 3 of 3: Classifying Animals Based on Their Scientific Names
Step 1. Start with the scientific name of the animal
The last two taxonomic levels of animals, genus and species, which are the most specific of all, are used as scientific names for animals. In other words, the official name of an animal recognized by scientists around the world is "genus" (which is written with a capital letter) followed by "species" (which is not capitalized). For example, the scientific name of modern humans is Homo sapiens because it comes from the genus "Homo" and the species "sapiens". Remember, the scientific name of the animal must be written in italics.
- Since the genus and species of animals are the most specific taxonomic levels, these two pieces of information alone are usually sufficient for most purposes.
- If you don't know the scientific name of the animal you want to classify, try searching the internet. Look for the animal's common name (eg "dog") followed by "scientific name". You can find the scientific name of the animal easily using this method.
Step 2. Use the animal's scientific name as a starting point for your research
Since an animal's scientific name is its species and genus, if you know the animal's scientific name, these two pieces of information are usually enough to start your search for the next taxonomic level.
Step 3. Determine the classification of animals from the lowest level using your observations
Once you know an animal's scientific name, you can also determine its taxonomic classification by observing its morphology, evolutionary history, and genetic relationships with other animals to find out its family, order, and so on. Use the information you know about the species to aid your research. If possible, check your suspicions using an appropriate textbook or biological source of information.
- For example, in the Homo sapiens example used here, if we knew that the closest evolutionary ancestor between humans and great apes was the same, we could include Homo sapiens in the family containing great apes (chimpanzees, gorillas, and orangutans). Because great apes are primates, we can include Homo sapiens in the primate order. From here, the class and phylum are easy to determine. Of course, all primates are mammals, so we can say that humans are in the class mammal, and all mammals are vertebrates, so we can say that humans are in the phylum chordata.
- As explained at the beginning of this article, all animals are in the kingdom animalia, regardless of other taxonomic classifications.
