Introduction to Classification

Taxonomy

• Study of biological classification

importance of biological classification

• groups organisms together with common features

• makes organisms easier to study

two branches of taxonomy

• systematic and nomeclature

nomenclature refers to

• naming of biological organisms

systematics

• placing of organisms into groups based on similarities and differences

Binominal System

invented by Swedish naturalist Carl Linnaeus

• consists of a Genus Name which is underlines

• followed by a species name also underlined

• GENUS NAME IS CAPITALIZED WHILE THE SPECIES NAME IS NOT

2 advantages of Binominal System

• universal

• no two species have the same name

• different developmental stages can have different names

Order of Taxa

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

define species

• a group of closely related organisms which are capable of interbreeding and producing fertile offspring

• basic unit of classification

• unit of biodiversity

What happens when populations are separated and stop interbreeding?

• gene pool diversifies due to mutations and natural selection and over generations may end up becoming different species

what is a subspecies

A population of a species that has distinct traits but can still interbreed with other populations of the same species.

breeds

• artificially created stock of animals or plants with a distinct appearance usually created by human selective breeding

hybrid

• offspring resulted from a cross between closely related species - usually infertile eg mule

Phylogenetic

• classification system based on evolutionary relationships

Phenetic

• based solely on morphological or other observable traits

Natural Vs Artificial Classification System

Natural	Artificial
show evolutionary relationships	ignore these natural relationships like common ancestry
designed to highlight common ancestry	purely for convenience
phylogenetic and phenetic	only phenetic
based on easily observable characteristics, molecular biology, genetics, fossil records	based on easily observable characteristics
vertebrates	Protoctista

Advantages of Whittaker Five Kingdom System

• first taxonomist to separate eukaryotes and prokaryotes

• first to give fungi their own kingdom

• simplicity

• first step toward an accurate classification system

• includes kingdom protoctista

Disadvantages of Whittaker 5 Kingdom System

• viruses aren’t included

• no place for symbiotic organisms

• prions aren’t included

• no distinction between two major prokaryotic groups

• sometimes based on superficial

• places together algae and protozoans

What are the main limitations of the currently used system of classification

1. Only as accurate as the current knowledge about each group of living organisms allows

2. Taxonomy may be subjective when a taxonomist has to choose how many and which criteria are important and which are not

General Limitations of a Dichotomous Key

1. Usually based on drawing/picture, limiting the morphological features which can be used

2. Key constructed can only be used with the organisms presented. It is useless if other species need to be identified

3. There is great morphological variation between members of the same species

4. Specimens are presented in a different orientation some features may not be visible in some organisms while visible in others

5. Organisms may have different features at different stages in the life cycle - thus limiting the accuracy of dichotomous key