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Home , Aspidelaps lubricus, Ursus (mammal)

Ch. 15 Classification Systems

Taxonomy

Why Classify?

• 2.5 million known ! • Another 20 million unknown species! • We need a system of biological classification that names and orders organisms in a logical manner. – Universally accepted name. – Groups with real biological meaning

1 Biological Classification • Early biological classification used a lot of detail. – Example: “Oak with deeply divided leaves that have no hairs on their undersides and no teeth around their edges” – Problems with this system • Too difficult to use. • Different scientists used different descriptions for the same organism. • Latin is used in classification. – Understood by scientists everywhere.

Carolus Linnaeus (Carl von Linne)

• Binomial nomenclature – Each organism has a two part name. – species – Must be italicized – The first letter of the genus must be capital. – Examples: Acer rubrum (red maple), Acer palmatum (leaf that resembles a human hand)

2 Carolus Linnaeus

• Organisms that share characteristics are grouped together. • Taxa – the group to which an organism is assigned. • – the science of naming organisms and assigning them to these groups. • Current classification rules governed by the International Codes of Zoological or of Botonical Nomenclature (ICZN or ICBN)

Linnaeus’ Classification System – Hierarchy • Species – population of organisms that share similar characteristics and that can breed with one another.**

3 Linnaeus’ Classification System – Hierarchy • Genus – Similar species but cannot breed with one another. – Examples: domesticus (house ) and Felis concolor (mountain ) – Examples: arctos (Grizzly ) and Ursus americanus (Black bear) • Similar feet, teeth and claws but are distinct species.

Linnaeus’ Classification System – Hierarchy • Families – Groups of genera (genus plural) which share many common characteristics. – Examples: leo () , Panthera tigris (), Felis domesticus (house cat), and Felis concolor (mountain lion) • Belong to the family (catlike ) – Examples: Ursus arctos (), Ursus americanus (Black bear) and melanoleuca () • Belong to the family Ursidae (Bear like animals)

4 Linnaeus’ Classification System – Hierarchy • Order – Several families of similar organisms. – Example: Felidae () and (). – Examples: Ursus arctos (Grizzly bear), Ursus americanus (Black bear), Ailuropoda melanoleuca (Giant panda) and vulpes (Red ) • Belong to the order (meat eaters)

Linnaeus’ Classification System – Hierarchy

• Class – Grouping of orders – Examples: Ursus arctos (Grizzly bear), Ursus americanus (Black bear), Ailuropoda melanoleuca (Giant panda), Vulpes vulpes () and Sciurus carolinensis (grey squirrel) • Belong to the class Mammalia • A “class of vertebrate, air-breathing animals whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair and/or fur, three middle ear bones used in hearing, and a neocortex region in the brain.” - Wikipedia

5 Linnaeus’ Classification System – Hierarchy • Phylum – several classes can be placed into a phylum – Examples: Ursus arctos (Grizzly bear), Ursus americanus (Black bear), Ailuropoda melanoleuca (Giant panda), Vulpes vulpes (Red fox), Sciurus carolinensis (grey squirrel) and lubricus (coral ) – Belong to the phylum chordata (Have a nerve cord)

Linnaeus’ Classification System – Hierarchy

• Kingdom – All phyla belong to one of the six kingdoms.

6 The Species Dilemma. • There is a debate among scientists on the definition of a species. • Some closely related species interbreed. – Example: Different species of mice may interbreed, some species of monkey interbreed. • Some organisms within a species are slightly different and some may consider them a separate species. – Example: Birds of the same species may have slightly different coloration.

The Species Dilemma.

• Some organisms reproduce asexually. – Example: bdelloid rotifers are all female and produce embryos without the need for sperm. • What about microorganisms such as bacteria? – Classifying them by what they eat (metabolism) is not easy. • Example: Some E.Coli are harmless while others are deadly. Both eat the same type of food. – They all look alike. – Rarely reproduce sexually.

7 8 Phylocode

• Linnaeus lived a century before Darwin’s publication of Origin of the Species. • Push for a new system based on evolutionary relationships not based on common characteristics. • Phylocode – Names organized based on evolutionary relationships – Look for common ancestors and group into “clades” – International Society for Phylogenic Nomenclature

9 The Species Dilemma

• The solution may be to define a species using several approaches.

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