INTRODUCTION:

Human beings generally tend to categorize the things in the world around them, and biologists are no different.  There are so many different kinds of living organisms that it takes a sophisticated system to categorize all of them in a way that all biologists can agree upon.  This system of classification is called taxonomy.
 

OBJECTIVES:

By the end of this series of labs, you should be able to:

Explain how the system of taxonomy works
Understand how binomial nomenclature works
Define binomial nomenclature and give examples
 

METHODS:

In this and following labs you will use textbooks and specimens to study this system of taxonomy, and explore a tiny bit of the diversity of living things on earth.  You will find it useful to refer to your textbook when you are stuck, but you should not attempt to look up all of the information requested.  Instead, look carefully at the specimens provided first to see if you could obtain information from them.
 

PROCEDURE:

What is taxonomy?

Taxonomists group organisms into categories, or taxons, according to the characteristics they have in common, starting with the most general and then getting more and more specific.  It might make more sense if we first consider a non-biological example.

Suppose that we wanted to classify different kinds of musical artists, so that everyone could understand the relationships between, say, the Rolling Stones and Garth Brooks.  There are lots of ways to do this; one way would be to start with broad categories, like blues music, and then keep splitting each category until we arrive at the narrowest category possible, such as a certain artist.  We might come up with a system like this (obviously a lot of things are missing here, this is just a simplified example):
 
 

So, according to this musical taxonomy, Gangsta Rap and House Music have more in common than, for example, Disco and Grunge, because Grunge and Disco follow paths that split way up at the Blues music category (their common ancestor).

The easiest way to think about this may be as an upside-down tree, so that the thickest part of the trunk is the most general.  When the trunk splits into branches, it is getting more specific, and you keep splitting until you get to each individual leaf at the end of each tiny twig, which is as specific as you can get.

Eventually we come to the most specific category possible (each “leaf”), within which all individuals are very much the same and very hard to tell apart (like all bad Elvis impersonators).

In biology, this most specific category is called a species, and it is defined as a group whose members can successfully breed with each other.

The system we use to classify organisms has several levels, the most general being the Kingdom and the most specific being the species.  There are also several levels in between, as listed below:
 

Domain Separates organisms on the most fundamental characteristics, such as the actual way they read the DNA, for example. There are 3 Domains, each containing one or more Kingdoms.
Kingdom We will be studying 5 kingdoms from 2 domains:  Kingdom Eubacteria from Domain Bacteria, and Kingdoms Protista, Fungi, Plantae, and Animalia from Domain Eukarya.
 Phylum There are several phyla within each Kingdom (these groups are often called “Divisions” in Kingdom Plantae).
  Class A Phylum can contain many smaller Classes.

   Order There are many Orders within each Class.

    Family A Family is a grouping of several related Genus categories.

     Genus A Genus contains related Species.

      Species The smallest possible grouping, containing members that can successfully breed with each other.
 

Each of the levels above is also sometimes split or grouped, using prefixes, such as super- or sub- or infra-, so we can have a Superfamily that contains several Families, but is still a narrower category than the Order or Suborder which contains it.

Once we have grouped organisms into these types, we can tell which are most closely related to each other, because the groupings are based on how similar organisms are to each other, as well as how similar their presumed ancestors were.  For example, a wolf and the family dog can be in the same Genus, but a wolf and a fox are in different Genera, although they share the same Order.  Wolves and rhinoceroses are in the same Class, but in different Orders, while wolves and spiders are in different Phyla within the Kingdom Animalia.  This simplified tree illustrates the relationship between these examples:
 

Every species of organism has a scientific name (which are traditionally in Latin, and no, this is not specifically meant to drive you up the wall).  This scientific name consists of two parts (just like people:  Jesse Jackson has 2 names, and just saying Jesse is not an effective way of telling somebody which person you mean, and neither is just saying Jackson).  This system of Binomial nomenclature ( bi = 2, nomial = name ) was used by an 18th century Swedish botanist named Linnaeus, and has been adopted worldwide.  Hence every organism has a two-part name, consisting of a genus, and the species, like Homo sapiens for humans. ( Note:  Even though man is commonly called Homo Sapiens, this is not entirely scientifically accurate, since *all* mankind currently exists as one sub-species, Homo sapiens sapiens.  Homo sapiens with the one “sapiens” is believed to be extinct.  But we digress).

These binomial names are always underlined if handwritten, or italicized in print.  Notice that the Genus part of the name is capitalized, but not the species part.  Here is how we stand in this scheme of things:

Domain Eukarya
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Mammalia
Order Primata
Family Hominidae
Genus Homo
Species sapiens

And if one wants to be called entirely scientifically accurate,
Sub-species sapiens

DISCUSSION QUESTION:

What, according to you, are the advantages and disadvantages of using this form of classification?  Can you come up with alternative methods of classification?