Taxonomic Classification

Objectives

Outline the binomial system of nomenclature.

List seven levels in the hierarchy of taxonomy – kingdom, phylum, class, order, family, genus, and species – using an example from two different kingdoms for each level.

Design and apply a key to distinguish a group of up to eight organisms.

Naming thingsTaxonomy: the science of classifying

living things (from Greek taxon meaning group (plural = taxa)

Organisms are classified by similarity.Many attempts from Greek times.

Ex: is something animal, mineral, or vegetable?

The idea of a 2-word description for every living thing

was devel- oped around 1750 by Carrolus

(Carl) Linnaeus of Sweden.The Linnaean system is called

binomial nomenclature (two- name naming system); uses Latin.

Naming thingsBinomial nomenclature

Linnaeus preceded Darwin & didn’t know evolution, but classification by similarity supports this theory.

Homologous structures: bird & bat wings - same bone structure so there was a common ancestor.But, must also consider analogous structures: Bats and butterflies both have wings, but are unrelated.

DNA similarities support classifications.DNA mutates at a known rate; the more similar the sequences of DNA – the more closely related the creatures will be.Mutations pinpoint where creatures broke from some common ancestor.

Naming thingsWhy name organisms?

Human need (for communication);beginning with the

Book ofGenesis 2:20. →→So scientists can communicate without

misunderstandings.

For example, the words inu (Japanese), chien

(French), perro (Spanish), and dog (English) all

represent the same 4-legged barking animal.

But Canis lupis familiaris (Latin) is recognized by any scientist anywhere.

Adam naming the animals

Naming thingsWhy name organisms?

The same word can be used differently even

in English-speaking countries.

Ex. American wheat is called “corn” in England.

Even in America, things have different names among

various regions or even age groups.

Ex. Roly-poly, pillbug, or wood louse =

Porcellio scaber

Naming thingsWhy choose Latin for naming things?

Throughout the middle ages, Catholic monks

kept Roman & Greek wisdom

alive copying texts in monasteries. The Catholic church

spoke & wrote in Latin. Scientists

had religious

educations.

Binomial nomenclatureThe Linnean system has two main

characteristics.1) Each kind of organism has 2-part name, a

binomial.1st part, the genus; 2nd part, the species - in Latin.1st letter of the genus is capitalized, & both names are italicized (or underlined) and latinized.

Ex: Linnaeus assigned to humans the scientific

name Homo sapiens, meaning

“wise man”.

Taxonomic hierarchiesThe Linnean system has two main

characteristics.2) Species are organ-

ized hierarchically into broader and

broader groups of organisms.

Closely-related species are grouped

into the same genus.Ex: the leopard,

belongs to a genus that includes the

lion (P. leo) & the tiger (P. tigris).

Hierarchyexample #1, the panther

Taxonomic hierarchiesThe Linnean system has two main

characteristics.The genus is one part

of a family – the cat family (Felidae), along

with house cats, etc. Families combine to form

an order – Carnivora, the meat eaters, including dogs. Orders form a class – Mam-

malia, whose creatures all

have fur and produce milk.Classes form a phylum, in

this case the Chordates, all having a spinal column.

Hierarchyexample #1, the panther

Taxonomic hierarchiesThe Linnean system has two main

characteristics.Several phyla – chordates,

arthropods, different worms,

sponges, etc. – form a king- dom, in this case Animalia,

which are heterotrophic and whose cells lack a cell wall.

The plant kingdom has cells that are

autotrophic; the cell wall is of cellulose.

The kingdoms of Animalia, Plantae,

Fungi, etc. form a domain, in this case

Eukarya – all the creatures whose

cells contain a nucleus.

Hierarchyexample #1, the panther

Taxonomic hierarchiesThe taxonomy of Mankind

Domain= EukaryaKingdom = AnimaliaPhylum = ChordataClass = Mammalia(up to this point we are

united with felines)

Order = PrimatesFamily = HominidaeGenus = HomoSpecies = sapiens

Hierarchyexample #2, the human

Taxonomic hierarchiesBranches on the tree of

life represent major changes in the way

creatures develop as a result of evolution.

Mutations happen, & the environment

changes.

Taxonomic hierarchiesMutations led to changes in the animal

kingdom

Dichotomous keysA dichotomous key is a method for

identifying and classifying objects, where each feature selected to help identification requires a choice between two alternatives.

A substitute teacher asks, “Which boy is James?”

Proceed step-by- step to find him,

always making one of two choices.

1, 2, 4, 8

Go to #:Go to #:

Dichotomous = “two branches”.

Dichotomous keysWhat should you

ask here?

Dichotomous keysWhat should you

ask here?

Taxonomic Classification (part 2)

Taxonomic hierarchiesBranches on the tree of

life represent major changes in the way

creatures develop as a result of evolution.

Mutations happen, & the environment

changes.

Three Domains with Six Kingdoms of Life

Note characteristics!

Remember: viruses are not alive; they have no kingdom.

Six Kingdoms of Life2 kingdoms for prokaryotes (all

unicellular with a cell wall) are distinguished by habitat.

Archaebacteria (archae = ancient) Domain ArchaeaLive in extreme environments

similar to early earth: hot springs, salty seas; oxygen is poisonous.Autotrophic (chemoautotrophic).

Eubacteria Domain BacteriaLive all around us: on the floor,

in our mouths, on our skin, etc.Auto- or heterotrophic.

Six Kingdoms of LifeDomain Eukarya: Cells with a nucleus; 4

kingdoms are distinguished by cellularity and nutrition.

Plants are multicellular autotrophs (photosynthetic).Fungi are heterotrophic decomposers with extracellular digestion (most are

multi- cellular; yeast are unicellular).Animals are multicellular

heterotrophs; most digest their food

within special-ized cavities. No cell wall.Protists are either auto-

trophs (algae) or hetero-trophs (like

amoebas).All but seaweeds are

unicellular.

Dichotomous keys (Review)To set up a dichotomous key, choose

questions that differentiate the subjects.Does it have: 1) a backbone? No. It’s a lancelet.

Yes. Go to #2. 2) a jaw? No. It’s a lamprey.

Yes. Go to #3. 3) legs? No. It’s a tuna.

Yes. Go to #4. 4) an amniotic egg?No. It’s a salamander.

Yes. Go to #5. 5) hair ? No. It’s a turtle.

Yes. It’s a leopard.

CladogramsA cladogram is a diagram that links

groups of organisms by showing evolutionary linkages branched off from common ancestors.

Can be based uponphysical characteristics.

CladogramsA clade is a group of species that includes

a single common ancestor.

CladogramsCladograms can be formed using similarities in the genetic code – the DNA – which translates into proteins. This is evidence for evolution.

Cladograms

A key for several animal animal phyla.

Based on: Presence of tissuesSymmetryBody cavityFetal development

Changes in classificationThe classification system has changed over the years.

Linnaeus only recognized two kingdoms: plants and animals.Today there are six kingdoms. Protista may be sub-divided one day into three or more new kingdoms.