the development of modern taxonomy

The Development ofModern Taxonomy

Mr.G.Burgess2004

Why Taxonomy? Taxonomy is the branch of biology that is

responsible for the naming and classification of organisms.

There are millions of organisms on our planet; from several microns to several meters in length.

Naming of organisms allows scientists to place the organisms into groups based on similarities.

Taxonomy in the beginning

4th century BC-Greek philosophers- Aristotle studied animals.- Aristotle, classified organisms by where they

lived; air-dwellers, land-dwellers, water-dwellers- Theophrastus studied plants- Theophrastus classified plants by stem structure;

woody stems, soft stems, shrubs with many woody stems, and trees.

- However, as the number of classified organisms grew, these methods of classification became cumbersome.

New beginning Technological advances made the classifications

systems of the philosophers obsolete. Development of the microscope and refining of

lenses enabled scientists to begin examining microscopic life.

A new way of categorizing organisms was needed.

John Ray 1600’s, English naturalist Identified >18000 different plants. Used the term species to identify each

group of organisms that were structurally similar and were able to pass their characteristics on to offspring.

Carolus Linnaeus The father of taxonomy Also classified organisms by structural similarities Changed the way organisms were named. Organisms were originally given lengthy Latin names Linnaeus shortened these by using a 2 name system

for organisms.

Binomial Nomenclature System of using two names for each organism. The term genus had been used since Aristotle to

describe groups of organisms with similarities and John Ray had used the term species.

Linnaeus used both terms for binomial nomenclature so that scientists could all know what plant / animal was being discussed.

Binomial Nomenclature (con’t)The system for naming was as follows.

1. All names are comprised of 2 names; genus, species

2. When writing the names; always capitalize the genus and leave the species small lettered.

3. Underline both words when in print or put an ‘sp’ after the species name. When typed, the names are italicized.

Modern Classification

With the development of the theory of evolution, scientists began visualizing more and more similarities between organisms and developed a classification scheme that began with the species(individual) and ended with the Kingdoms(very large sets of organisms with commonalities).

**As the classification group gets SMALLER, the number of similarities between its members gets LARGER.

1. Structural similarities: the look of the organism

2. Cellular similarities: similar organelles

3. Biochemical similarities: similar chemical products (ie. Blood chemistry determines ancestry)

4. Similar embryologic development

5. Genetic similarities: similar number of chromosomes and inherited traits.

Dichotomous Key Tool used to identify organisms Usually a list of paired questions that describe the

structures found on the organisms.

Bibliography

johnray.gif, http://www.strangescience.net/biopics/johnray.gif, April 6, 2004.

linnaeussmall.jpg, http://www.ucmp.berkeley.edu/history/linnaeus.html, University of Berkley Museum of Paleontology, April 6, 2004

Biology the stuudy of life, rervised 3rd edition, W.D.Schraer, and H.J.Stoltze, 1990. Chapter 6 pp.90-102.

Wikipedia the free encyclopedia, http://en.wikipedia.org, April 6, 2004

Taxonomy:Classifying Life, users.rcn.com/.../BiologyPages/ T/Taxonomy.html , April 6, 2004.

Image1.gif, http://www.csuchico.edu/~mw97/Biol_142/Image1.gif, April 7, 2004.