History of Classification

Finding Order in Diversity

History of Classification

• For more than 3.5 billion years, life on Earth has been constantly changing.

• Natural Selection has led to a staggering diversity of organisms.

• Biologists have identified and named about 1.5 million species so far

• Estimate that 2 and 100 million have not yet been discovered.

Classification

1. Why classify?a. By using a scientific name,

biologists can be certain that everyone is discussing the same animal.

b. Taxonomy• A discipline of classifying

organisms and assigning each organism a universally accepted name.

History of Classification

2. How are living things organized for study?a. When you hear the

word “bird”, what mental picture appears? • A flying animal that has

feathers

History of Classification

b. In a good system of classification, organisms placed into a particular group are more similar to each other than they are to other organisms in different group.– EX: We use a classification system. When you

refer to “teachers”, or more specifically “zoology teachers”.

History of Classification

c. By the 18th century, European scientists realized that referring to organisms by common names was confusing. Common names vary among languages.

– For example a cougar can also be called a puma, a panther or a mountain lion.

History of Classification

• In England, the word buzzard refers to a hawk whereas in many parts of the US, buzzard refers to a vulture.

History of Classification

Aristotle’s System1. The first attempt at standardizing scientific

names basically described the physical characteristics of a species. – EX: scientific name of a particular tree might be

“Oak with deeply divided leaves that have no hairs on their undersides and no teeth around their edges.”

History of Classification

Carolus Linnaeus• Swedish botanist who

lived during the 18th century.– binomial nomenclature• Classification system

in which each species is assigned a two-part scientific name.

1. Linnaeus’s System of Classification

• Classification system with 7 levels

• Each level called taxon (plural: taxa)

• Why 7 levels?– Lots of organisms

Classification System

• Kingdom Phylum

Class Order Family

Genus Species

• Country State

County City Neighborhood

StreetHouse #

Kingdom

• Largest taxonomic group, consisting of closely related phyla– Eukaryotes

• 2 original kingdoms– Animalia– Plantae

Phylum

• Group of closely related organisms that share important characteristics

• Ex: Chordata – Humans & Bears

Class & Order• Class – group of similar orders– Mammalia

• Internal regulation of body temp. (warm-blooded)

• Have body hair• Produce milk for young

• Order – broad taxonomic category composed of similar families– Carnivora

• Bears - Ursidae• Dogs – Canidae • Cats - felidae

Family • Share many

characteristics• EX: Bears – Ursidae

and Ailuropoda– Polar bears– Grizzly bears– Panda bear

Genus & Species• Genus– Group of closely related species, and the first part of the

scientific name in binomial nomenclature.• Species – Group of organisms that can breed and produce offspring

that are fertile.

Grizzly BearUrsus arctos

Polar BearUrsus maritimus

Giant PandaAiluropoda melanoleuca

Binomial Nomenclature• 2-word naming system• Each species is assigned

a 2 part name• Always written in italics

or underlined– First word is always

capitalized– Genus species

Grizzly bear ~ Ursus arctos

Questions???

• How are organisms classified?– Living things are classified according to shared characteristics and

organized into 7 categories.

• What is binomial nomenclature?– A two-word naming system

• Explain the difference between Aristotle’s system and Linnaeus's system of classification?– Aristotle’s common name system which can differ due to in

languages.– Linnaeus’s system of binomial nomenclature

Modern Evolutionary Classification

What characteristics do scientists use to classify organisms?

Modern Classification

• Organisms choose with whom they will mate.• Group organisms according to biologically

important characteristics. • Linnaeus’s system grouped animals according

to visible similarities and differences.– Problems???

Modern Classification• How would you classify the crab, limpet, and

barnacle?

LIMPET

CRAB

BARNACLE

Look more closely!

Limpet and barnacle larvae are very different.

Barnacles have jointed limbs. Limpets DON’T !

Barnacles have a segmented bodyLimpets DON’T !

Barnacles have an exoskeleton that molts.Limpets DON’T !

LIMPET

CRAB BARNACLE

Look more closely!

Crab and barnacle larvae are very similar

Barnacles have jointed limbs. So do CRABS !

Barnacles have a segmented bodySo do CRABS !

Barnacles have an exoskeleton that molts.So do CRABS !

Modern Classification

Modern ClassificationEvolutionary Classification• Darwin’s ideas about descent with modification

gave rise to the study of phylogeny.– The study of evolutionary relationships among

organisms.

Evolutionary relationship of the Phylum Chordata

Modern Classification

• Evolutionary classification– Method of grouping organisms together according

to their evolutionary history.– All members of a genus share a recent common

ancestor.

Modern Classification• Cladogram–Diagram that shows

the evolutionary relationships among a group of organisms.

• Derived character– Characteristic that

appears in recent parts of a lineage, but not in its older members. Derived

Characters

Modern Classification

• Similarities in DNA and RNA– Genes of many organisms show important

similarities.– DNA can be used to determine classification and

evolutionary relationships.

Are these organisms related?

Similarities in DNA can be used to help show evolutionary relationships and how species have changed.

African vulture American vulture Stork

Traditionally these first two were classified together in falcon family.Storks were put in a separate family.

American vultures have a peculiar behavior. When they get overheated, they urinate on their legs to cool off

African vulture American vulture Stork

The only other bird that does this is the STORK.

DNA comparisons showed more similarities between American vulture and stork DNA than DNA from the two kinds of vultures suggesting a more recent common ancestor between storks and American vultures.

African vulture American vulture Stork

Questions???

1. What characteristics do scientists use to classify organisms.– Biological:

• Structure (including similarities in DNA)• Physiological• behavioral

– Evolutionary relationships; phylogeny

2. How are evolutionary relationships important in classification?– Accurate placement of organisms within their phylogenic tree.

Domains and Kingdoms

What are the three-domain systems of classification?• Bacteria• Archae• Eukaryota

3 Domain System• Modern organisms have

been grouped according to how evolved

• Domain– More inclusive category;

larger than a kingdom.• 3 Domains:

1. Bacteria – unicellular & prokaryotic

2. Archaea - extremophiles3. Eukarya – unicellular &

multicellular Eukaryotes

3 Domain System

1. Eubacteria– Domain of unicellular prokaryotes that have cell

walls containing peptidoglycans

3 Domain System

2. Archaea• Domain of unicellular prokaryotes that have cell

walls that do not contain peptidoglycan • They live in extreme environments.

Colonies of haloarchaea on agar plates

3 Domain System

3. Eukarya Domain of all organisms whose cells have nuclei,

including protists, plants, fungi and animals.

Tree of Life

6 Kingdoms of Life

• The six-kingdom system of classification includes:1. Eubacteria2. Archaebacteria3. Protista4. Fungi5. Plantae6. Animalia

Domain Eukarya

Kingdom Protista

• The kingdom Protista is composed of eukaryotic organisms that cannot be classified as animals, plants or fungi,

• They can be unicellular or multicellular; photosynthetic or heterotrophic; and can share characteristics with plants, fungi or animals.

Kingdom Fungi

• Kingdom composed of heterotrophs; many obtain energy and nutrients from dead organic matter (decomposers).

• They can be either multicellular (mushrooms) or unicellular (yeasts).

Kingdom Plantae

• Members of the Kingdom Plantae are multicellular, photosynthetic autotrophs that have cell walls containing cellulose.

• Plants are nonmotile – they cannot move from place to place.

Kingdom Animalia

• Members of the Kingdom Animalia are multicellular eukaryotic heterotrophs whose cells do not have cell walls.

• There is great diversity within the animal kingdom, and many species exist in nearly every part of the world.

Questions???

1. What are the three-domain systems of classification?– Bacteria, Archae and Eukarya

2. What are the six kingdoms of life? • Eubacteria, Archaebacteria, Protista, Fungi, Plantae,

Animalia