Ch. 18 Classification Systems• Classification in biology, is the

identification, naming, and grouping of organisms into a formal system.

• The vast numbers of living forms are named and arranged in an orderly manner so that biologists all over the world can be sure they know the exact organism that is being examined and discussed.

• Modern classification has its roots in the system of Carolus Linnaeus (Carl von Linné), who grouped species according to shared physical characteristics.

The father of modern taxonomy

Taxonomy• Hierarchy is a ranking system

• Taxonomy - The hierarchical system of naming, describing and classifying organisms using structural characteristics

• The groups to which organisms were assigned are called taxa (singular: taxon)

• Linnaeus ranked the categories from the broadest and most general taxa (kingdoms) to the smallest the most specific taxa (individual species).

Taxonomic Level of Order

• Kingdom• Phylum• Class• Order• Family• Genus• Species

KingPhilipCame OverForGreenSpaghetti

Binomial nomenclature(Naming System)

• Binomial nomenclature in its simplest form is a way of naming a species by means of two names both in Latin or Greek.

• The use of Latin or Greek names were used because these languages were understood by scientists everywhere

• The first name, which begins with a capital letter is known as the Genus it is always capitalized.

• The second part represents the Species is always printed with all letters in lower case.

• The scientific name must be either underlined or written in italics.

Ursus arctos

Grizzly Bear

Great White Shark

Carcharodon carcharias

What Separates One Species from Another Species?

• Species-group of organisms that share similar characteristics and can breed with one another and their offspring can reproduce offspring.

• When organisms from different species breed with one another their offspring are sterile or infertile.

= Mule

Male Donkey XFemale Horse

= Hinny

Male Horse XFemale Donkey (jenny)

Female Liger Male Liger

Female Tiger

X

Male Lion

Tiglons or Tions

Male Tiger X Female Lion

Zedonk / ZonkeyZebroid / Zorse

Female Horse

X

Male Zebra

Female Donkey

X

Male Zebra

Beefalo or Cattalo

Bison

X

Domestic Cow

White Bass

X

Striped Bass

Hybrid Striped Bass

Most taxonomist use a five-kingdom system. These five-kingdom group organisms together that have similarities in such fundamental characteristics as major cellular structure, unicellular or multicellular and methods of obtaining nutrients, and now DNA evidence.

Recent Advances

• The Three-Domain System:• Domain – a more inclusive

category than any other – larger than a kingdom.

1. Domain Bacteria – includes the kingdom Eubacteria (true)

2. Domain Archaea – includes the kingdom Archaebacteria (ancient)

3. Domain Eukarya – includes the kingdoms Protista, Fungi, Plantae, and Animalia. P 459

Evolutionary Classification• Phylogeny – the evolutionary relationships among

organisms.• Biologists now group organisms into categories that

represent lines of evolutionary descent, or phylogeny, not just physical similarities.

• This strategy is called Evolutionary Classification.• Cladistic analysis identifies and considers only those

characteristics of organisms that are evolutionary innovations – new characteristics that arise as lineages evolve over time, these are called Derived characters.

• Derived characters can be used to construct a cladogram, a diagram that shows the evolutionary relationships among a group of organisms.

cladograms

Dichotomous Key (Taxonomy Key)

• A tool that is used by scientists that work in the field when they come across a unfamiliar organism.

Web Links

• http://www.nps.gov/cave/desertlb/reveg/rv_wq1.htm