Chapter 14

CLASSIFICATION OF ORGANISMS

Why Classify?•Why group things?• Easier to find information• Easier to identify organisms• Shows evolutionary relationship

It is impossible for biologist to memorize every name of the estimated 10-30 million organisms on Earth!• Taxonomy = Science of naming and classifying organisms

• Aristotle – (350 B.C.E) first scientist to group organisms as either plants or animals

• Carolus Linneaus – father of modern taxonomy• Swedish botanist (1701-1778) - Saw

importance in having a universal system of naming organisms• Grouped things according to structural

similarities• He developed a system of classification and

naming.• Binomial Nomenclature = two word name for

each species

Modern Taxonomy•We still look at structural similarities but primarily we look at evolutionary relationships to classify organisms

• Ex: homologous structures• Embryology• DNA similarities

Binomial Nomenclature = two-word name for each organism• Organisms are named according to Genus and Species• Genus = a group of closely related species, first part of the scientific

name, capitalized• Species = second part of a scientific name, lower case• Scientific names are always italicized or underlined • ex: Homo sapiens or Homo sapiens• Homo = genus name• sapiens = species name

Binomial Nomenclature• Felis, Musca, domestica, americanus

• What’s up with these funny sounding names?

• They are either Latin or Latinized words that describe the organism they identify.

• Latin words still used today:• Agenda - Things to be done• Alibi – elsewhere• Bona fide - Genuine, sincere• Carpe Diem - Seize the day• Ego - Consciousness of one's own identity• In vitro - In a test tube (literally means "in glass")• Rigor mortis - The rigidity of death

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What’s Up with Latin!?!• We use Latin because no one speaks Latin

anymore.

• The words never change their meaning and there is no confusion.

• These terms are also descriptive.

• What do you think the names domestica and americanus tell us about those organisms?

Rules for Binomial Nomenclature• Names consist of two words—Genus and species.• Both words are italicized or underlined.• Genus is always capitalized.• species is always lower-case• Both names are in Latin or Latinized.• Two different organisms cannot have the same name.• The species name has to be different within the same Genus.

Scientific NamesHomo sapien

s

Panthera leo

Musca domestic

aAcer

rubrum

People

HouseFly

Lion

Red Maple

Classification Categories• Different levels from the most general to more specific characteristics and from largest to smallest.• Eight levels of taxonomy are: (example in red)•Domain – Eukarya•Kingdom – Animalia•Phylum – Chordata•Class - Mammalia•Order – Primata • Family - Homidae• Genus - Homo• Species – sapiens

Classification• You need to know each level—taxon—of classification.• So, come up with a phrase that helps you remember the levels in order.• I like to use King Philip Came Over For George’s sword (Kingdom-Phylum-Class-Order-Family-Genus-species)• Remember, each level is called a taxon.• Each taxon contains the organisms in the taxon below.• So, if two organisms are in the same family, they are also in the same order, class, phylum and kingdom.

Examples and Meanings• One great thing about classifying organisms is that the taxon names have meanings that describe the organisms in those taxa.• The following six slides show the classification of great white sharks, striped bass, the common house fly, the blue crab, chimpanzees and humans.• All are in the Kingdom Animalia (animals).• Hopefully you will notice the similarities and differences contained in the meanings of their scientific names. Enjoy!

3 Domains (developed in 1990)• Archaea – unicellular prokaryotes that have cell walls that do not contain peptidoglycan• Kingdom Archaebacteria• Bacteria – unicellular prokaryotes that have cell walls containing peptidoglycan.• Kingdom Eubacteria• Eukarya – includes all of the organisms with eukaryotic cells--that is, those with membranous organelles (including mitochondria and chloroplasts). Domain of all organisms whose cells have nuclei, including protists, plants, fungi, and animals• Kingdoms Protista, Fungi, Plantae and Animalia

Six Kingdoms• Kingdom Archaebacteria (archae – ancient)• Prokaryotes, cell walls without peptidoglycan (peptide chain that makes up the cell

wall)• Live in extreme environments: thermophiles, halophiles, acidophile• Kingdom Eubacteria• Prokaryotes, cell walls with peptidoglycan• Ex. Streptococcus and E. coli

• Kingdom Protista• Simple, many are unicellular, no specialization of tissuses• Ex. protozoans, algae

• Kingdom Fungi• Multicellular heterotrophs that have a cell wall (absorb food through cell wall)• Ex. Mushroom, molds, and yeast

• Kingdom Plantae• Multicellular organisms, contain chlorophyll, have organs and tissues, autotrophs• Kingdom Animalia• Multicellular, organisms, heterotrophs, have organs and tissues

LIVING THINGS

Are categorized by

Important Characteristi

csSuch as

PROKARYOTIC CELLSAnd

differing

Cell wall structures

Which place them in

Domain Bacteria

Which coincide with

Kingdom Eubacteria

Domain Archaea

Which coincide with

Kingdom Archabacteri

a

EUKARYOTIC CELLS

Which place them in

Domain Eukarya

Which is subdivided into

Kingdom Fungi

Kingdom Protista

Kingdom Plantae

Kingdom Animalia

http://www.pbs.org/wgbh/nova/nature/classifying-life.html

HumansKingdom: AnimaliaPhylum: ChordataClass: MammaliaOrder: PrimatesFamily: Hominidae (great apes and humans)Genus: Homo (“man”)Species: sapiens (“knowing” or “thinking”)

ChimpanzeeKingdom: AnimaliaPhylum: ChordataClass: MammaliaOrder: PrimatesFamily: Hominidae (great apes and humans)Genus: PanSpecies: troglodytes (“cave man”)

Seems that the scientific name for chimpanzees comes from people originally thinking that chimps looked like “cave men”!!!

Blue CrabKingdom: AnimaliaPhylum: ArthropodaSubphylum: Crustacea (lobsters, crabs, shrimp)Class: MalacostracaOrder: Decapoda (“ten legs”)Family: Portunidae (swimming crabs)Genus: Callinectes (“beautiful swimmer”)Species: sapidus (“delicious”)

Common Housefly

Kingdom: AnimaliaPhylum: Arthropoda (“jointed foot”)Subphylum: Hexapoda (“six-legged”)Class: InsectaOrder: Diptera (flies with one pair of wings)Family: Muscidae (stocky flies with large eyes)Genus: MuscaSpecies: domestica (“domestic”)

Striped Bass (Rockfish)Kingdom: AnimaliaPhylum: ChordataClass: Osteichthyes (fish with bones)Order: Perciformes (perch-like fish)Family: Moronidae (temperate basses)Genus: MoroneSpecies: saxatilis (“dwelling among rocks”)

Great White SharkKingdom: Animalia Phylum: Chordata Class: Chondrichthyes (fish with cartilage instead of bones)Order: LamniformesFamily: LamnidaeGenus: Carcharodon (“ragged tooth”)Species: carcharias (“shark”)

How Do Scientist Categorize organisms?

Cladogram• Depicts evolutionary relationships among groups. • It is based on Phylogeny, which is the study of evolutionary

relationships.• They show how members of a group change over time,

giving rise to new groups.• More closely related groups appear closer together, while

more distantly related groups are farther away.• CLADISTICS is form of analysis that looks at features of

organisms that are considered "innovations", or newer features that serve some kind of purpose. (Think about what the word "innovation" means in regular language.) These characteristics appear in later organisms but not earlier ones and are called DERIVED CHARACTERS. • http://ccl.northwestern.edu/simevolution/obonu/cladograms

/Open-This-File.swf

Cladogram• All groups on a cladogram share a common ancestor• Branches divide into two branches at a point called a node• At a node, a group that branches off has a characteristic its ancestors do not have, known as a derived character.• Derived character- a trait found in new species but not in the

ancestral species• Cladograms reveal clades. • Clade- includes a single common ancestor and all of its living and

extinct descendants.• Organisms in the same clade are more closely related than

organisms in different clades

Clade vs. Class• A clade may be different from a class

Common Ancestor 1

shark Ray-finned fishes Amphibians

common ancestorReptile/Arcosaur

TurtlesBony Shell common

ancestorReptile with

scales

Snakes Lizards

Common ancestorArcosaur

Crocodiles Birds

Mammals

Dichotomous Key• A dichotomous key is a biological tool that allows the user to determine the identity of an unknown item from a list of items. "Dichotomous" means "divided into two parts". • Each step in the key refers to one physical characteristic.• A dichotomous key gives two choices in each step to direct the

user to the correct name of the specimen. • The characteristics in the key should be arranged in steps

from most general to most specific.