Classification

Vocabulary

Prokaryote – unicellular organisms without a nucleus

Eukaryote – unicellular or multicellular organisms with a nucleus

Vocabulary

Autotrophs – “self feeder” organisms that can make their own food through photosynthesis

Heterotrophs – “other feeder” organisms that must ingest (eat) their food

Why Do We Classify Things?

Placing items in categories is natural for humans.

Wild animals: domesticated animals

Edible plants: poisonous plantsFresh water fish:salt water fishThere are numerous examples of

classification systems.

The First Classification System

The first classification system developed 2,500 years ago by Aristotle.

Organisms were separated into two groups, Plants and Animals.

A statue of Aristotle, 384 – 322 BC

Aristotle He further placed animals into three

groups, those that fly, those that walk, and those that swim.

Aristotle

Plants were classified as trees, shrubs or herbs depending on size and structure.

Linnaeus

But, more divisions were needed, and scientists would name organisms whatever they wanted.

A better system was needed that everyone could use.

In 1760 Carolus von Linnaeus published his book on classification.

Carolus von Linnaeus

(1707-1778)

Swedish scientist who laid the

foundation for modern

taxonomy

Binomial Nomenclature

Binomial “two names”Nomenclature is a system

of namingCarolus von Linnaeus Two-word naming system

– GenusNoun, Capitalized,

Underlined or Italicized– Species

Descriptive, Lower Case, Underlined or Italicized

Why Do We Classify Organisms?

Biologists group organisms to represent similarities and proposed relationships.

Classification systems change with expanding knowledge about new and well-known organisms.

Tacitus bellus

Why a Scientific Classification System?

Ambiguity of terms– All scientists use the same system.

Latin “dead language”– The Latin terms will not change over

time Categorization of relationships:

– Evolutionary– Structural– Biochemical

Classification

Classification starts at the largest division that includes the most organisms.

Classification consists of three domains and six kingdoms.

BacteriaArchaea Eukarya

The Three Domains

The Six Kingdoms

How are organisms placed in kingdoms?– Cell type, prokaryotic or eukaryotic– The number of cells in their body, unicellular or

multicellular– Their ability to make food, autotrophs or

heterotrophs

EubacteriaArchaea Protist

aPlantaeFungi Animalia

The six-kingdom system

Classification

KingdomPhylumClassOrderFamilyGenusSpecies

KingPhillipCame OverFor Good Soup

The farther you go down the classification system the more specific the name becomes for that particular organism.

What is classification based on?

Classification Criteria

BiochemistryGenetic System, DNA and RNAEvolutionary HistoryNutritionMolecular Make-upA Dichotomous Key is used to

classify organisms

Classification System for Lynx and Bobcat

Kingdom: AnimaliaPhylum: ChordataClass: MammaliaOrder: CarnivoraFamily: FelidaeGenus: LynxSpecies: Lynx canadensis Lynx

rufus lynx bobcat

The same to this point, the animals share the same characteristics

Family or Genus Relations?

Family:Less closely

relatedLarger groupGenus:More closely

relatedPrecedes

species=interbreeding

Family:FelidaeLions, tigers,

leopardshouse

cats,cheetahs, ocelots

Genus: PantheraLeopards

(pardus)Lion (leo)Tigers (tigris)

Feline Family Members:

Genus: Panthera Lions and Tigers

The First Cat

Most authorities agree that the domestic cat descended from the Caffre cat, a small breed of African wildcat. The Caffre cat was domesticated in ancient Egypt, possibly as early as 2500 BC.

Evolutionary History

The evolutionary history of a species is called its phylogeny.

Cladistics is a system of taxonomy that reconstructs phylogenies by inferring relationships based on similarities.

Taxonomic Diagrams

Biologists group organisms into categories that represent common ancestries, not just physical similarities.

Early naturalists used physical characteristics and later, fossil data, attempting to represent evolutionary relationships among organisms.

Taxonomic Diagrams

Today, modern classification systems use fossil data, physical characteristics and DNA/RNA information to draw increasingly more accurate branching diagrams.

Two types of diagrams are Cladistic and Phylogenic diagrams

Cladistics

Cladograms are based only on characteristics observable in existing species.

The branching patterns in a cladogram are defined by the presence of unique, characteristics shared by all members of the group.

Cladistics

A branching diagram to show an evolutionary family tree is known as a cladogram.

Cladistics hypothesize that every phylum originated from a single group of organisms that has branched into today’s species.

Cladograms

Each branch point or fork in the cladogram, shows a point in evolution where a unique characteristic developed to separate one group from another.

Cladograms are concerned with the order structural differences happened.

Cladogram

Cladogram

Cladogram

Taxonomic Diagrams

Phylogenetic trees, or phylogenies, represent hypothesized evolutionary relationships among organisms and may include extinct as well as modern species.

A Phylogenic Tree

A Phylogeni

c Tree

A Phylogenic Tree