Biology 14.1 Classification of Organisms

Classification of Organisms

Taxonomy Just as it is impossible for postal

workers to sort mail by only a person’s name; it is impossible for biologists to memorize every name of the 10-30 million organisms on Earth.

To sort mail, a postal worker first sorts by zip code, than by street number, than by name.

In the same way, biologists sort organisms into large categories, than split those categories into other categories, and continue sorting into smaller and smaller more specialized categories.

Taxonomy More than 2000 years ago, the

Greeks grouped plants and animals according to their structural similarities.

Later Greeks and Romans grouped plants and animals into basic categories such as oaks, dogs, horses, birds, fish and so on.

Eventually each unit of classification came to be called a genus; the Latin word for “group”

Starting in the Middle Ages, genera were named in Latin.

Taxonomy The science of naming and

classifying organisms is called taxonomy.

Until the mid-1700s, biologists named organisms by adding descriptive phrases in Latin to the name of the genus.

The name of the European honeybee was Apis pubescens thorace subgriseo abdomine fusco pedibus posticic glabis untrinque margine ciliatus.

These names became so long that they become difficult to use and not everyone used the same name. A simpler solution needed to be developed.

Taxonomy In the 1750s, a simpler solution

was developed by a Swedish biologist, Carl Linnaeus.

Linnaeus developed a naming system that used only two words for each species; a system called binomial nomenclature

This two part name system became popular among scientists and is used today under the title “scientific name”.

The scientific name for the same honeybee is Apis mellifera; much shorter than the previous old system and easier to remember.

Taxonomy The first word in the two-part name

of a scientific name is the genus.

A genus is a category of taxonomy that contains similar species.

Organisms in a genus share similar characteristics.

For example the genus Quercus is composed of different kinds of oak trees.

The second word in a scientific name identifies one particular kind of organism within the genus called a species.

Genus Quercus

Quercus Palustris

Taxonomy The first letter of a genus name is

always CAPITALIZED and the first letter of the species name is always lowercase. A scientific name is also always italicized or underlined.

For example: Quercus is the genus name for oak trees

Quercus rubra is the name for a red oak.

Quercus phellos is the name for a willow oak.

Quercus is the genus name ; phellos and rubra are the species names

Genus Quercus

Quercus Palustris

Taxonomy The scientific name of an organism

gives biologists worldwide a way to talk about the same animals while using different languages. It is a universal naming system.

The name given to a species must conform to the rules established by an international commission of scientists,

All scientific names must have two Latin words or terms created according to the rules of Latin grammar.

To the right are newly discovered species of spiders named for rock-stars Neil Young and David Bowie Heteropoda davidbowie

Jason Bond, an ECU professor of biology, has named a newly discovered trapdoor spider, Myrmekiaphila neilyoungi, after the legendary rock star.

Classifying Organisms

Linnaeus worked out a system of classifying plants and animals in which an organism’s form and structure are the basis for ranking.

The different groups that all organisms fall into can be arranged by 8 levels.

Species are at the bottom. Remember species are a group of similar organisms that are capable of interbreeding.

A member of a species can breed with another member of the same species.

Domain

Classifying Organisms All species are members of a

genus; a larger group that contains many species similar to each other.

Remember that our 2 part scientific name lists the genus than the species.

For example, Parthera pardus is the scientific name for a species of panther.

Pardus is the species name and panthera the genus name .

Similar genus are collected into a family. The family Felidae at right houses all varieties of felines (cats large and small; housecats to lions)

Domain

Classifying Organisms

The family of felines is part of a larger order. An order has many families in it.

The order in the example at right is the order of carnivora which contains carnivores (meat eaters)

An order always contains similar families.

Domain

Classifying Organisms

After order comes class. A class has many different orders under it.

In the example at right; the class is mammalia (mammels)

The order of carnivora is just one of many orders that fall under the class of mammalia

Domain

Classifying Organisms Classes with similar

characteristics are grouped together into a phylum.

The class of mammalia at right is just one of the many classes that make up the phylum of chordata

Domain

Classifying Organisms The next step up the ladder is the

kingdoms.

Many phylums that are similar are grouped together into a kingdom.

In the example at right the phylum chordata is just one of several phylum in the kingdom of animalia (animals)

Domain

Classifying Organisms Last, but not least, all kingdoms

are grouped together into a domain.

All living things are grouped into one of three domains.

Two domains, Archaea and Bacteria, are each composed of a single kingdom of prokaryotes.

The third domain, Eukarya, contains all four kingdoms of the eukaryotes.

Domain

Classifying Organisms In order to remember the 8

categories in order, it is useful to memorize a phrase.

Do Kindly Pay Cash Or Furnish Good Security is a helpful way to remember the order of

1. Domain2. Kingdom3. Phylum4. Class5. Order6. Family7. Genus8. Species

Domain

Classifying Organisms Scientific names are powerful

because they tell us much about an organism.

Each level of classification is based upon characteristics shared by all members of the classification.

For example; the order carnivora contains all members that eat meat; ie are carnivores.

The class mammalia contains all members that are mammels.

The family felidae contains all members that are felines (types of cats ranging from housecats to lions)

Domain

Classifying Organisms For another example; let’s

look at the classification of a common honeybee.

The honeybee’s scientific name, Apis mellifera, indicates it belongs to the genus Apis and the species name is mellifera. Together they give us the scientific name of the genus-species combined.

Genus: Apis- All members of this genus are actually honey bees, living alone or in hives

Classifying Organisms

Family: Apidae- Honey bees are members of the group Apidae because they have a corbicula (pollen basket) on the outside of each hind appendage.

Classifying Organisms Order: Hymenoptera-

Honey bees are members of the group Hymenoptera because they have “membranous wings, and their abdomen's first segment is fused with the last segment of the thorax.

Classifying Organisms Class: Insecta- Honey

bees are members of the Insecta because: they don't have any muscles past the first segment of their antenna; they have something called Johnston's organ; and they have an internal structure inside the head called a tentorium.

Classifying Organisms Phylum: Arthropoda-

Honey bees are members of the Arthropoda because they have segmented bodies and a jointed exoskeleton.

Classifying Organisms

Kingdom: Animalia- Honey bees are members of the Animalia because they are, multicellular, heterotrophic and motile at some point in life.

Domain:  Eukaryota- Honey bees are members of the domain Eukaryota because their cells have a membrane-bound nucleus

Classifying Organisms

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1. Domain2. Kingdom3. Phylum4. Class5. Order6. Family7. Genus8. Species