Classification of Living Things

Why do we classify things?

Supermarket aisles Libraries Classes Teams/sports Members of a family Roads Cities Money

What is classification?

Classification: putting things into orderly groups based on similar characteristics

Taxonomy: the science of describing, naming, and classifying organisms according to their characteristics and evolutionary history

Early classification

Aristotle grouped everything intosimple groups such as animals or plants

He then grouped animals according to if they had blood or didn’t have blood, and if they had live young or laid eggs, and so on…

Modern Classification System Developed by Carolus

Linnaeus

Swedish Biologist 1700’s

Grouped organisms into hierarchical categories

Starts broad and ends specific

Modern Taxonomy

The Evidence used to classify into taxon groups   1) Embryology   2) Chromosomes / DNA   3) Biochemistry   4) Physiology   5) Evolution   6) Behavior

The modern system of classification has 8 levels:

DomainKingdomPhylumClass

OrderFamilyGenusSpecies

Helpful way to remember the 8 levels

Dumb kids playing catch on freeways get squashed

Or…make up your own…

D K P C O F G S

Scientific Names: Binomial Nomenclature

An organism’s genus is always written first; the organism’s species is always written second

The genus is Capitalized; the species is written in lower case

Homo sapiens

Representing Evolutionary Relationships:

Phylogenetic Tree:

- Family tree showing evolutionary history

- shows relationships thought to exist between groups or organisms

Representing Evolutionary Relationships:

Cladogram:

- Uses shared derived traits

- Derived traits indicate divergence from a common ancestor