Wednesday, August 03, 2011

Working with extinct animals: Basics (5): Names and Taxonomy

Dino Evolution:
What are the two main orders of dinosaurs and what does each name mean?

Dinosaurs are divided into two Orders – the Ornithischia (Bird-Hipped) and the Saurischia Order (Lizard-Hipped).  The Saurischia Order contains meat eaters and plant eaters.  The two Suborders of Saurischia are Theropoda (theropods) and Sauropodomorpha (sauropods).  Theropods, like T-rex, are carnivores, and also are the ancestors of modern birds.  Meanwhile sauropods, such as Apatosaurus, are huge four-footed plant eaters.

The Ornithischia Order has a hip structure much like birds, but are not their ancestors.  This Order is divided further into three Sub-Orders.  The Ornithopoda, such as Iguanadon, walked two feet, using their stiff tails for balance.  Meanwhile, the Marginocephalia, like Triceratops, had oddly-shaped skulls with frills and horns.  Finally, the Thyreophora, like Ankylosaurus, are noted for their armored bodies and spiked tails.

Linnaean Organization:
What are the seven levels in the Linnaean classification system? What does binomial nomenclature mean?
Here is the full Linnaean classification for human beings.
*Kingdom- Animal
*Phylum- Chordata
*Class- Mammalia
*Order- Primate
*Family- Hominidae
*Genus- Homo
*Species- Sapiens sapiens

In biology, there are two major ways of classifying organisms.  The method that most people are familiar with is the one devised by Carlos Linnaeus in the 1770s.  Known as the Linnaean System, organisms are grouped by shared characteristics.  The hierarchy from bottom up starts with the most specific qualities and ends with the most general ones.

Since problems have cropped up with this system, phylogentic systematics was developed in the 1950s.  This system of cladistics grouped living things by common ancestors.  The presentation of this system is a cladogram of a tree with branches.

Linnaeus Hierarchy
The classification system devised by Linnaeus originally had seven levels starting with Kingdom at the highest, and ending with Species at the lowest.  In 2004, Domain was added as the highest level.  At present, there are three Domains – Bacteria, Archaea (organisms without defined cell-nucleus), and Eukarya (complex organisms).  Ten Kingdoms comprise the Bacteria Domain, three for the Archaea Domain, and about twenty-eight for the Eukarya Domain.  Kingdoms are, in turn, divided into Phylums.  In the Animalia (animals) Kingdom, there are about thirty Phylums.  Classes make up the Phylums, and are divided into Orders.  The Orders are divided into Families, and Families into Genera (Genus).  The Genera are divided into the final level of the hierarchy: Species.  A Species is defined as a group of similar individuals that can interbreed in the wild.

Binominal Nomenclature
A formal naming system for organisms, binominal nomenclature presents a two part scientific name for each species.  Since common names such as “robin” are confusing, binomial nomenclature is used instead.  The first name, which is capitalized, is the genus of the organism.  The second name, which is in lower case, describes a characteristic of the species.  Together the two names provide a clear and unique name for an organism.  A full binomial name also includes who discovered the species and when.  For example: English sparrow is Passer domesticus (Linnaeus, 1758).

Binominal nomenclature is not a system for classifying organisms.  It only names them, and does not order living things into groups.  Meanwhile, taxonomy is both a nomenclature and classification system.

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