Classification of Living Things

Taxonomy and Cladograms

What is Taxonomy?

For millennia humans have created different ways to describe the living things on our planet.

At first our attempts to organize and classify animals were simple and based solely on their external appearance.

We now use a more complex system.

Why Do We Need to Classify Things?

The main reason is that knowing which species are related to each other, and how closely they are related, is very useful to the Scientific community.

If you were trying to find out what was wrong with a whale it would be useful to know that it is a mammal and not a fish.

Carolus Linnaeus

Carolus Linnaeus 1707 - 1778

Every recognized species on Earth is given a two-part scientific name. This system is called "binomial nomenclature."

Carolus Linnaeus (1707–1778) introduced the concept of binomial nomenclature in his great work called Systema Naturae.

In this book, nature was divided into three kingdoms: mineral, vegetable, and animals.

Linnaeus also established five ranks: class, order, genus, species, and variety.

Taxonomic Hierarchy

A Taxonomic hierarchy is very similar to a family tree.

Through it you can track how closely related each species is to each other.

Depending on how detailed you wish to be, this can be a simple tree chart, or a complex one (tolweb.org is an example of a complex one).

Do Kings Play Chess On Fine Glass Surfaces?

This year you will be responsible to remember the following taxonomic hierarchy:

Domain (Do) Kingdom (Kings) Phylum (Play) Class (Chess) Order (On) Family (Fine) Genus (Glass) Species (Surfaces)

So How Does It Work?

Each level of the hierarchy has several groups and these groups each have specific characteristics required to be part of them.

If we found a new living organism we would compare its characteristics to these groups to see where it fits.

If it was endothermic (warm blooded), fed its young milk, had hair and gave live birth we would probably classify it as a mammal.

We Just Keep Learning

Since Linnaeus we have continued to add new groups to the taxonomic hierarchy.

As we continue to learn and develop new tools for investigation (like DNA analyses) we often have to change how we describe an organism from a taxonomic point of view.

Chimpanzee vs. Lion

Domain: Eukarya Kingdom: Animalia Phylum: Chordate Class: Mammalia Order: Primates Family: Pongidae Genus: Pan Species: troglodytes

Domain: Eukarya Kingdom: Animalia Phylum: Chordate Class: Mammalia Order: Carnivora Family: Felidae Genus: Panthera Species: leo

Comparative Taxonomy

By comparing the Chimpanzee to the Lion we can see that though they are very different creatures, they have some key things in common.

Both are animals with chordates (vertebrates) and mammals.

Yet one is a primate (apes and monkeys) and the other a carnivore (meat eaters).

Evolutionists use these similarities and differences to determine the relationships between species.

Broad to Specific

Each level of the taxonomic tree gets more and more specific.

Domain, Kingdom, Phylum and Class are very large groups with broad characteristics (we’re mammals too).

But by the time you get to Genus and Species the characteristics get very specific. See the next slide.

Cheetah vs. Lion

Domain: Eukarya Kingdom: Animalia Phylum: Chordate Class: Mammalia Order: Carnivora Family: Felidae Genus: Acinonyx Species: jubatus

Domain: Eukarya Kingdom: Animalia Phylum: Chordate Class: Mammalia Order: Carnivora Family: Felidae Genus: Panthera Species: leo

Comparative Taxonomy 2

As you can see the cheetah and lion share more in common than the lion and chimpanzee did.

Yet despite both being Felidae (cats) they are each part of a different Genus and a unique species.

The Species level is very specific.

Scientific Names

Each living creature on our planet has been given a Scientific name in Latin.

The Genus and Species of a creature are combined to create the Scientific name (thank you Linnaeus).

Panthera leo – lion Acinonyx jubatus - cheetah

Why Latin?

Each living creature on the planet has several names. A lion is known as a leone in Italian and an ingonyama in Zulu.

This could lead to confusion amongst our world’s scientists.

Since Latin is a dead language, meaning it will never change as it is not actively spoken, scientists use it to name things.

This name means the same thing, no matter where you are on Earth.

Cladograms

Cladograms

Cladograms are tree-like charts that generally show the evolutionary relationships between different creatures or taxonomic groups.

They can be drawn artistically, simply, or extremely complexly (tolweb.org).

Basic Cladogram for Great Apes

HumanChimpanzee BonoboGorillaOrangutan

Interpreting a Cladogram

Interpreting a Cladogram

Some cladograms give extra details. The one above showed that all three

creatures possessed a backbone as they come after the trait.

However only the horse and human shared the placenta characteristic.

Thus humans are more closely related to horses than to fish in an evolutionary sense.

Resources

www.hawaii.edu www.torontozoo.com www.nationalzoo.si.edu www.tolweb.org