5M – Taxonomy & scientific names

Supporting article M: Understanding Scientific names and Taxonomy

http://www.biology4kids.com/files/studies_species.html

Scientists have all these complex ways of organizing living things. They look at your physical traits, how you develop as a fetus, or in an egg. They look to see if you are a plant.
But there is one big thing that helps them determine whether you are in the same species as another animal or plant. You are the same species as another being if you can do a really important thing. You can reproduce and have babies. Also, those babies have to be able to have more babies. They have to be fertile.

If you are a type of fern, scientists would know that another fern is the probably the same species if the two ferns can create a similar fern that is fertile. The same rules apply if you are a mouse. Not all mice can have fertile babies together. They can’t have babies because there are different types of mice. And of course there is you. You can’t have babies with a dog. You can’t have babies with a horse. You can’t have babies with a monkey that looks a lot like your brother or sister. You can only have offspring (babies) with other humans. You two would be the same species.

So remember, everything we talked about here describes a living system. Scientists are always re-evaluating and developing the classification system. Science will always change and evolve as new facts are discovered. Even the idea of a species is difficult.

There is no sure fire way to say, “Here is where one species ends and another begins.” Some species are so closely related that they can have fertile offspring. Species are defined by man, and it is often difficult to make clear definitions when two organisms are incredibly similar. If those organisms reproduce and create a completely new line of creatures, those parents actually were not that different when it came time to mix up the genes.

It’s never black and white.  In all of biology and the world, there is overlap. Coming up with definite black and white answers that always work rarely happens. You can get definite answers in math. You can even get definite answers in physics. Biology has many gray areas. Scientists will always debate and try to improve ideas and explanations. You may learn about ligers. Ligers are the offspring of lions and tigers but they are not fertile offspring. Those two organisms are incredibly similar, genetically, but their differences are enough to make them separate species.

RULES OF TAXONOMY
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Every known living organism on Earth is classified and named by a set of rules. Those rules are used by all scientists around the planet. The names are called scientific names, not common names. Common names are the ones you might use when talking with your friends. You call your pet a dog or a cat (the common name). Scientists call those animals by a set of several names like Canis familiarus. That’s a dog.

SCIENTIFIC NAMES
Scientific names follow a specific set of rules. Scientists use a two-name system called a Binomial Naming System. Scientists name animals and plants using the system that describes the genus and species of the organism. The first word is the genus and the second is the species. The first word is capitalized and the second is not. A binomial name means that it’s made up of two words (bi-nomial). Humans are scientifically named Homo sapiens. You may also see an abbreviation of this name as H. sapiens where the genus is only represented by the first letter.

TAXONOMY
The taxonometric way of classifying organisms is based on similarities between different organisms. A biologist named Carolus Linnaeus started this naming system. He also chose to use Latin words.

Taxonomy used to be called Systematics. That system grouped animals and plants by characteristics and relationships. Scientists looked at the characteristics (traits) that each organism had in common. They used the shared derived characteristics of organisms. Scientists were then able to find the common ancestry of the organisms. So if you had a nose, scientists would trace back all creatures that had a nose. Then they thought that you were related to them (because you all had noses). Organisms are now organized by a combination of observable traits and genetics, not one superficial trait (like a nose).

So, Taxonomy is the science of classifying organisms. The system currently used by taxonomists is called the Linnaean taxonomic system, in honor of Swedish biologist Carolus Linnaeus (1707 — 1778). The Linnaean system breaks down organisms into seven major divisions, called taxa (singular: taxon). The divisions are as follows:

Major Taxonomic Levels

  • DIAGRAMME

Note: There are many subdivisions of the seven main taxonomic levels, such as Subphylum, Subclass, Infraclass, and so on. You may see many of these other sublevel taxa listed in the taxonomic tree of an organism.

The classification levels become more specific towards the bottom. Many organisms belong to the same kingdom, fewer belong to the same phylum, and so on, with species being the most specific classification. A species is one group of genetically distinct, interbreeding organisms. The average genetic differences within a species are less than the average differences between that species and a closely related group of organisms.

The classifications also tell something about the degree of relation between different organisms. For example, two animals that belong to the same family and genus are more closely related than two animals that simply belong to the same family.

Here are two examples of the Linnaean taxonomic system of classification, for humans and armadillos:

Common Name:

Human

Nine-Banded Armadillo

Kingdom:

Animalia

Animalia

Phylum:

Chordata

Chordata

Class:

Mammalia

Mammalia

Order:

Primata

Cingulata

Family:

Hominidae

Dasypodidae

Genus:

Homo

Dasypus

Species:

Homo sapiens

Dasypus novemcinctus

Note: Cingulata used to be called Xenarthra, named for a small bony bump found on the vertebrae of some members of this order. Before that, Cingulata was known as Edentata, meaning “without teeth”. Both of these earlier names have fallen out of favor: Xenarthra is now elevated to the level of a superorder, while Edentata is not accurate, as most cingulates do in fact bear teeth. Many sources will still incorrectly list Xenarthra or Edentata as the order.
The taxonomic tree above tells us that humans and armadillos are related, but not closely. We share the same class, but belong to different orders.

Most of the information at the higher levels is not included in the standard description of an organism. For most plants and animals, just listing the family, genus or species is enough to let biologists know what the other levels should be. The most common way to list the taxonomic name of an organism is to list the genus and species; this is known as binomial nomenclature, meaning a two-name system. When using this listing, the genus should always be italicized and capitalized, while the species is not capitalized. You may have noticed that in the example above I included the genus name in with the species. This is the preferred way of listing species, to avoid confusion. There could possibly be another organism with the species name sapiens, for example, but there is only one Homo sapiens.

The taxonomic names are usually in Latin, although species are often named after the person who first described them. Using Latin helps to give a general description of the organism through its taxonomic classification. For example (using the nine-banded armadillo again):

Common Name:

Nine-Banded Armadillo

Translation:

Kingdom:

Animalia

Animals: Multicellular, heterotrophic, eukaryotic organisms.

Phylum:

Chordata

Chordates: animals with a notochord.

Subphylum:

Vertebrata

Vertebrates: Animals with bony spines.

Class:

Mammalia

Mammals: animals that have hair and give milk to their young.

Subclass:

Eutheria

Placentals: Mammals in which the young develop in a placenta inside the uterus.

Superorder:

Xenarthra

Xenarthrans: Anteaters, armadillos, and sloths. Named for their xenarthrous processes, a small bony bump on the vertebrae that is unique to this group.

Order:

Cingulata

Cingulata: Pampatheres (extinct), glyptodonts (extinct) and armadillos.

Family:

Dasypodidae

From Dasypodis, Greek for “turtle-rabbit”; Linnaeus did not like the Aztec name, Azotochtli, and so used a Greek equivalent to name the family.

Genus:

Dasypus

Dasypus is derived from the same Greek root as the family name.

Species:

Dasypus novemcinctus

Novem: nine; -cinctus: band. Nine-banded.

The descriptive names work for other species as well. So long as you understand some Latin, you can learn a lot about an organism from its scientific name. For example, look at our own species name: Homo sapiens. Homo means “self” or “same”, meaning “the same as me” — which, for you, means “human”. Sapiens means “wise”. Therefore, Homo sapiens means “Wise human”.

Now that you know a little more about the taxonomic system, you can impress your friends! When they say, “Hey, look at that critter! What is it?” you can reply, in a calm and official-sounding voice, “That’s a D. novemcinctus, no doubt about it.”