An Introduction to Classification

November 29, 2010

How many organisms are there in the world?

There are thought to be between 2 and 100 million species on

earth

Approx. 50 000 VertebratesApprox. 1.4 million Invertebrates – 1 million insects!Only approx. 5 000 mammals.

Classification System

Why classify organisms?In order to organize the vast number of species according to biological similarities and differences

To make studying them easier

To provide information about related organisms and ancestry

The Science of Classification

Taxonomy through the years...

First:Aristotle first introduced two key concepts of modern taxonomy

Classification of organisms by typeBinomial Definition (what does that mean?)

Wrote “History of Animals”

Classified animals according to similarities:

Those that flyThose that live on land/waterNO GENETIC RELATIONSHIPRelated organisms that may not be genetically relatedWhat about those that don't fit the general classification?

Named animals according to Family and Difference:

First by similarities, then differentiate specific characteristics

And then...Carolus Linaeus published “Systema Naturae” which organized all plants and animals from Kingdoms down to Species

Created essential system we use today, though not as detailed

First taxonomist to group humans with primates

Finally...Modern System brought more scientific understanding to Linnaeus' work

Connected classification to Darwin's Theory of Evolution

Began considering genetic connections between organisms

Modern Taxonomy

Begin by grouping organisms according to general characteristics

At each stage of classification, group organisms according to more specific criteria

Most specific level of classification – Species – are considered to be a morphologically and physiologically similar group of organisms that are able to produce offspring

Taxonomy

What systems do modern scientists use to classify organisms?

Taxonomic: based on structural and physiological similarities between organisms

Phylogenic: based on genetic connections between organisms

Phylogeny

Phylogeny is the branch of Biology where scientists study the evolutionary history of living organisms

Making Connections

Modern taxonomists can classify organisms by connecting them to evolutionary relatives

Several ways to do this...

Methods

Fossil RecordsCast a mold of organisms in rock and preserve structures to be studied and compared

Homologous StructuresParts of different organisms that show similarities in their structure

More Methods

Comparative EmbryologyClosely related organisms may have similar stages of early development

Comparative DNA and RNAInvestigates genetic similarities between organisms

What happens when scientists discover a new species that does not 'fit in' to the

current structure?

What are the levels of Classification?

General KINGDOM PHYLUM CLASS ORDER FAMILY GENUSSpecific SPECIES

How can we remember this? Acronyms!!

Allow us to create a phrase that we can more easily remember using the first letter of each word that we need to knowKingdom Phylum Class Order Family Genus SpeciesKing Phillip Came Over For Good SoupKids Playing Catch On Freeways Get Smashed

Now you try...

Create your own acronym usingKPCOFGS

Answer the following questions:

What does the acronym: Kids Playing Catch On Freeways Get SmashedStand for?

What is the science of classification called?

Who was Carl Linaeus and what was his contribution to the science of classification?

Dichotomous Keys

A map to follow when classifying organisms

At each stage organisms are differentiated according to more specific characteristics.

Scientists use them when they discover new species to determine the possible classification of their organism, and to create a map for other scientists that may want to classify that organism.

Binomial NomenclatureA two name system of identification

We name organisms according to Genus and Species. The first name is General, the second is Specific.

We use Latin terms for naming (it is the universal language of science)

Names are Italicized and the first letter of the Genus is capitalized.

Example: Homo sapiens