Chapter 18

Classification

Taxonomy - the science of classifying organisms and giving them a universally accepted name.

Aristotle (384 - 322BC)

Aristotle’s Groups He divided all living things into 2

major groups 1. Plants

classified by size and structure

2. Animals classified by habitat (where they

lived)

HISTORY: Aristotle Problems with his system:

Frogs live in both water and on land

HISTORY: Aristotle Problems with his system:

Bats, birds and flying insects were grouped together

HISTORY: Carolus

Linnaeus- developed the modern system of classification

Father of Taxonomy

Carolus Linnaeus (1707-1778)

MODERN CLASSIFICATION SYSTEM Organisms are grouped

together on the basis of: Similarity in structure

Felis domesticus

Felis rufusPanthera leo

Similarity in structure

Canis lupus

Similarity in structure

Canis latrans

Similarity in structure

Canis domesticus

Organisms are grouped together on the basis of:

Similarity of embryonic development

Organisms are grouped together on the basis of:

Similarity in evolutionary history

Phylogeny: the evolutionary

history of a species based on comparing relationships between species using the fossil record

Organisms are grouped together on the basis of:

Similarity in behavior

Classification is based on close evolutionary relationships of organisms.

Organisms classified in the same taxa (pl.) (taxon, sing.) share a common ancestry. They have evolved from the same common ancestral organism.

Binomial nomenclature - classification system developed by Carolus Linnaeus that assigns each organism a two-part name.

-Scientific name is ALWAYS in italics.

-Scientific name is ALWAYS in Latin.

-First word- CAPITALIZED, second word- lowercase

The first word is the genus in which the animal belongs to and the second word is the species in which the animal belongs to.

-Example- Homo sapiens (Humans)

Binomial Nomenclature

Scientific Name: Rudbeckia hirta

Common Name: Gloriosa daisy

or Black-eyed Susan

Binomial Nomenclature

Scientific Name: Pinus virginianis

Common Name: Virginia Pine

Binomial Nomenclature

Scientific Name: Harmonia axyridis Common Name: Asian Ladybug

Binomial Nomenclature

Scientific Name: Ophiophagus hannahCommon Name: King Cobra

Species Organisms that belong to the

same species can mate AND produce FERTILE offspring.

Horses and donkeys can mate. They produce a mule.

Mules are INFERTILE

+ =

Lions and tigers can mate. They produce a liger.

Ligers are INFERTILE

+ =

Why use scientific names? Common names do not indicate how

organisms are related or classified.

Common names can be misleading.

(e.g., seahorse, weeping willow)

Organisms with more than one common name leads to mass confusion.

Why Latin? Latin is no longer spoken, and

therefore, does not change as spoken languages do.

So, scientific names remain the same forever.

Linnaeus's System of Classification -hierarchical Kingdom Phylum Class Order Family Genus Species -Each of these levels is called a taxon

(taxa)

KingdomPhylum

ClassOrderFamilyGenusSpeci

es

K__________ p__________ c_________

o___________ f________ g_________ s________.

Kings play chess on fine gold sets.

K__________ p__________ c_________

o___________ f________ g_________ s________.

King Phillip came over for great soup.

-The kingdom is the largest of Linnaeus's taxonomic categories.

(Linnaeus named two kingdoms- Animalia and Plantae)

-His system was based on visible similarities and differences

Can you think of any problems with this?

All organisms, living or extinct, are descendants of the first cells. Because they all share a common ancestor, all organisms are related to one another, no matter how different they seem.

Relationships among taxa can be illustrated on a family, or phylogenetic tree.

-The tips of the branches represent the most modern organisms to evolve.

-The base represents common ancestors from which the organisms at the tip evolved.

-Each time a branch divides, it show the emergence of a new ancestral species.

Cladistic analysis - scientific search for ancestral relationships among species.

Cladogram - phylogenetic trees constructed from a two-way branch points that show the evolutionary relationships among a group of organisms.

Derived characters - homologous characteristics that unite the organisms in a group.

When a scientist is in the field and finds an organism they do not recognize, he/she uses a dichotomous key to identify it.

This key is a list of observable traits that eventually lead you to the name of the organism.

The observations are presented as choices.

Kingdoms and Domains Six kingdom system of classification: -Bacteria (Eubacteria) -Archaebacteria -Protist -Fungi -Plant -Animal

Domain Bacteria -polymerases are small and

simple -cell walls contain

peptidoglycan

Domain Archaea comes from a Greek work meaning

"ancient" live in extreme environments polymerases are complex and

similar to eukaryotes cell wall does not contain

peptidoglycan

Domain Eukarya all organisms have a nucleus

(eukaryotes) Protist, Fungi, Plant, and Animal.