Botany CH 17 – Classification of

Organisms

Taxonomy

The science of classifying and naming organisms Each group is called a taxon (pl. taxa)

What is Taxonomy ?

Metadata Taxonomy

Bloom’s Taxonomy

iPhone Taxonomy

Advertising Taxonomy

Early Taxonomy ( 384 – 322 BC )

Aristotle, a philosopher of Greek origin, began the organization process

He used only 2 taxa It was very inefficient as

common names varied from place to place

Early Two Taxa System

Linnaeaus, a Swedish botanist devised a system based upon form and structure

His goal was to join “ similar to similar” His original system had 7 levels

1 2 3 4 5 6 7

Linnaean System ( circa 1750 )

EMPIRE

KINGDOM

CLASS

ORDER

GENUS

SPECIES

VARIETY

This system still had 7 levels – but now slightly different

Linnaean – with an early change

EMPIRE

KINGDOM

CLASS

ORDER

GENUS

SPECIES

VARIETY

KINGDOM

PHYLUM

CLASS

ORDER

FAMILY

GENUS

SPECIES

Levels of Classification

While older systems were based on observed features

Recent DNA sequencing has uncovered natural relationships

So the system was re-organized into an 8 –level format

1 2 3 4 5 6 7 8

Taxonomic Reshuffle

greater dissimilarity greater similarity

(least alike) (most alike)

DOMAIN

KINGDOM

PHYLUM

CLASS

ORDER

FAMILY

GENUS

SPECIES

Modern System

ENGLISH NAME GROUPLATIN / GREEK

NAME

animals KINGDOM Animalia

chordates PHYLUM Chordata

vertebrates SUB-PHYLUM Vertebrata

mammals CLASS Mammalia

primates ORDER Primates

hominids FAMILY Hominidae

human GENUS Homo

wise SPECIES sapiens

So the DNA sequencing ( think Genome Project) data forced the change to a 3-domain system

This system is not based solely on observable features

These domains are: Domain Bacteria

Domain Archaea

Domain Eukarya

The 3 Domain System

These are prokaryotic organisms They lack a true nucleus They have cell walls They reproduce by binary fission

Domain Bacteria

These are also prokaryotic organisms They lack a true nucleus They have distinctive cell

membranes They reproduce by binary fission

Domain Archaea

These are the eukaryotic organisms They have membrane bound

organelles – including a membrane bound nucleus

Domain Eukarya

The 6 Kingdom System

Bacteria Archaea Eukarya

Eubacteria

Archaebacteria

Protista

Plantae Fungi Animalia

Eubacteria - means “true bacteria” Archaebacteria – means “ ancient

bacteria”

Prokaryotic Kingdoms

Protista Neither plants, animals, or fungi

Identified by what they are not

Fungi Get their nutrition by absorption

Plantae Most are autotrophic

Animalia Develop from embryos and have

symmetry

Eukaryotic Kingdoms

Naming System

Linnaeus also developed a naming system for the organisms in his classification system

It was called binomial nomenclature The “binomial” meant that every

organism would be identified by its genus and species

Linnaeus Revisited

The genus name begins with an uppercase letter

The species name is always lowercase Both would be underlined or italicized

Rana pipiens ( Northern leopard frog ) Escherichia coli ( Enteric rod bacteria )

Binomial Nomenclature

Systematics

Systematics is a way to classify organism by their relationship (evolutionary)

Systematics is based on inferences that are founded on homologous structures

Systematics

Homologous structures are organs or bones that appear in completely different organisms

It is these homologous structures that allows scientists to infer that these organisms had a “shared” ancestor

Homologous Structures

Examples

The inferred (evolutionary) history of a single species is known as phylogenetics

The prefix phylo means “tribe” or “race”

The suffix genetics means “origin”

Phylogenetics

Similarities between fossils and living species

Phylogenetic Evidence

Similarities in embryo

development

ontogeny recapitulates phylogeny

Phylogenetic Evidence

Similarities in chromosome sequences

Phylogenetic Evidence

Similarities in homologous structures

Phylogenetic Evidence

All phylogenetic trees are hypothetical

They will change with every new discovery

The Result Phylogenetic Tree

Cladistics

Cladistics is a system that uses shared characters and derived characters for its grouping

It was conceived in 1966 by a German biologist

Cladistics infers that organisms that share a derived characters inherited it from a common ancestor

Cladistics

A shared character is a feature that all members of the group have in common

Examples: hair in all mammals OR feathers in all birds

A derived character is an advanced trait that evolved within the group being analyzed

Example: loss of a tail

Cladistics

A clade is a group of organisms that share a common ancestor

The derived character is used to group those organisms into the clade

The Clade

Amphibians, turtles, lizards, snakes, crocodiles, birds and mammals have or historically had four limbs

Fossils show that snakes did have limbs Some modern snakes retain rudimentary

limbs Four limbs = a shared derived character

and was inherited from a common ancestor for this clade of vertebrates

A Vertebrate Clade

Vertebrate clade

Botany CH 17 – Classification of

Organisms End