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Chapter 18: Chapter 18: ClassificationClassification

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18–1 Finding Order in Diversity18–1 Finding Order in Diversity

Life on Earth has been changing for Life on Earth has been changing for more than 3.5 billion yearsmore than 3.5 billion years

1.5 million species named1.5 million species named between 2 and 100 million additional between 2 and 100 million additional

species have yet to be discovered species have yet to be discovered

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Why Classify?Why Classify?

organize living things into groups organize living things into groups that have biological meaningthat have biological meaning

Taxonomy = discipline of classifying Taxonomy = discipline of classifying organisms and assigning each organisms and assigning each organism a universally accepted organism a universally accepted namename

What is classification?

ClassificationClassification is the is the arrangement of organisms into arrangement of organisms into orderly orderly groupsgroups based on their based on their similaritiessimilarities

Classification is also known as Classification is also known as taxonomytaxonomy

Taxonomists Taxonomists are scientists that are scientists that identify & name organismsidentify & name organisms

Benefits of Classifying

Accurately & uniformlyAccurately & uniformly names names organisms organisms

Prevents Prevents misnomersmisnomers such as such as starfish & jellyfish that aren't starfish & jellyfish that aren't really fish really fish

Uses Uses same language (Latin or same language (Latin or some Greek)some Greek) for all names for all names

Sea”horse”Sea”horse”????

Early Taxonomists

2000 years ago, 2000 years ago, Aristotle was the first Aristotle was the first taxonomisttaxonomist

Aristotle divided Aristotle divided organisms into plants organisms into plants & animals& animals

He subdivided them He subdivided them by their habitat ---by their habitat ---land, sea, or air land, sea, or air dwellersdwellers

Early Taxonomists

18th century taxonomist

Classified organisms by their structure

Developed naming system still used today

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Binomial NomenclatureBinomial Nomenclature

Carolus Linnaeus, Carolus Linnaeus, – a Swedish botanist, 1700sa Swedish botanist, 1700s

binomial nomenclature = classification binomial nomenclature = classification system in which each species is system in which each species is assigned a two-part scientific nameassigned a two-part scientific name– written in italicswritten in italics– first word is capitalized (Genus), the first word is capitalized (Genus), the

second word is lower case (species)second word is lower case (species)

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Assigning Scientific NamesAssigning Scientific Names

Common names are confusing and vary Common names are confusing and vary among languages or even regionsamong languages or even regions– Ex: cougar, mountain lion, panther, pumaEx: cougar, mountain lion, panther, puma– different species sometimes share a single different species sometimes share a single

common name common name Ex: buzzard: hawk? Vulture?Ex: buzzard: hawk? Vulture?

Scientists have agreed to a single Scientists have agreed to a single name for each speciesname for each species

Use Latin & GreekUse Latin & Greek

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Scientific NamesScientific Names

grizzly bear is called grizzly bear is called Ursus arctosUrsus arctos – Ursus Ursus — is the genus — is the genus

Genus = group of closely related speciesGenus = group of closely related species

– arctosarctos – is the species – is the speciesunique to each species within the genus unique to each species within the genus Often a Latinized description of some Often a Latinized description of some

important trait of the organism or an important trait of the organism or an indication of where the organism lives indication of where the organism lives

– Ursus maritimus,Ursus maritimus, the polar bear the polar bearmaritimus,maritimus, referring to the sea referring to the sea

Which TWO are more closely related?

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Linnaeus's System of ClassificationLinnaeus's System of Classification

Hierarchical - it consists of levels Hierarchical - it consists of levels includes seven levels includes seven levels

– from smallest to largest—species, genus, from smallest to largest—species, genus, family, order, class, phylum, and kingdom. family, order, class, phylum, and kingdom.

– Each level is called a Each level is called a taxontaxon or taxonomic or taxonomic category category

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Ursus arctosUrsus arctos (Grizzly Bear) (Grizzly Bear)

Kingdom – AnimaliaKingdom – Animalia Phylum – ChordataPhylum – Chordata Class – MammaliaClass – Mammalia Order – CarnivoraOrder – Carnivora Family –UrsidaeFamily –Ursidae Genus –Genus –UrsusUrsus species - species - arctosarctos

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HumansHumans

Kingdom = AnimaliaKingdom = Animalia Phylum (Division for plants) = Chordata Phylum (Division for plants) = Chordata Class = Mammalia Class = Mammalia Order = Primates Order = Primates Family = Hominidae Family = Hominidae GenusGenus = = HomoHomo speciesspecies = = sapienssapiens

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Taxonomic groups Taxonomic groups above the level of above the level of species are “invented” species are “invented” by researchers who by researchers who decide how to decide how to distinguish between distinguish between one genus, family, or one genus, family, or phylum, and another.phylum, and another.

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Phylogeny = the study of Phylogeny = the study of evolutionary relationships among evolutionary relationships among organisms organisms

Biologists now group organisms into Biologists now group organisms into categories that represent lines of categories that represent lines of evolutionary descentevolutionary descent, or , or phylogeny, not just physical phylogeny, not just physical similarities. similarities.

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evolutionary classification = method evolutionary classification = method of grouping organisms together of grouping organisms together according to their evolutionary according to their evolutionary historyhistory

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The higher the level of the taxon, the The higher the level of the taxon, the farther back in time is the common farther back in time is the common ancestor of all the organisms in the ancestor of all the organisms in the taxon. taxon.

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Cladogram = diagram that shows the Cladogram = diagram that shows the evolutionary relationships among a evolutionary relationships among a group of organismsgroup of organisms

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The genes of many organisms show The genes of many organisms show important similarities at the important similarities at the molecular level. molecular level.

Similarities in DNA can be used to Similarities in DNA can be used to help determine classification and help determine classification and evolutionary relationships. evolutionary relationships.

The more similar the DNA sequences The more similar the DNA sequences of two species, the more recently of two species, the more recently they shared a common ancestor, and they shared a common ancestor, and the more closely they are related in the more closely they are related in evolutionary terms. evolutionary terms.

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Dichotomous KeyDichotomous Key

A dichotomous key is a tool that allows the A dichotomous key is a tool that allows the user to determine the identity of items in user to determine the identity of items in the natural world, such as trees, the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and wildflowers, mammals, reptiles, rocks, and fish. fish.

Keys consist of a series of choices that Keys consist of a series of choices that lead the user to the correct name of a lead the user to the correct name of a given item. given item.

"Dichotomous" means "divided into two "Dichotomous" means "divided into two parts". Therefore, dichotomous keys parts". Therefore, dichotomous keys always give two choices in each step. always give two choices in each step.

Dichotomous Keying

Used to identify Used to identify organismsorganisms

Characteristics given in Characteristics given in pairspairs

Read both Read both characteristics and characteristics and either go to another set either go to another set of characteristics OR of characteristics OR identify the organismidentify the organism

Example of a Dichotomous Key1a Tentacles present – Go to 21a Tentacles present – Go to 2

1b Tentacles absent – Go to 31b Tentacles absent – Go to 3

2a Eight Tentacles – Octopus2a Eight Tentacles – Octopus

2b More than 8 tentacles – 32b More than 8 tentacles – 3

3a Tentacles hang down – go to 43a Tentacles hang down – go to 4

3b Tentacles upright–Sea Anemone3b Tentacles upright–Sea Anemone

4a Balloon-shaped body–Jellyfish4a Balloon-shaped body–Jellyfish

4b Body NOT balloon-shaped - 54b Body NOT balloon-shaped - 5

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18–3 Kingdoms and Domains18–3 Kingdoms and Domains

There are now 6 Kingdoms – listed There are now 6 Kingdoms – listed below.below.

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Domain = most inclusive taxonomic Domain = most inclusive taxonomic category; larger than a kingdomcategory; larger than a kingdom

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EubacteriaEubacteria UnicellularUnicellular ProkaryoticProkaryotic Autotroph or heterotrophAutotroph or heterotroph Cell walls with peptidoglycanCell walls with peptidoglycan Examples: E. coli, Streptococcus, Staph Examples: E. coli, Streptococcus, Staph

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ArchaebacteriaArchaebacteria unicellular unicellular prokaryotic prokaryotic extreme environments extreme environments

– volcanic hot springs, brine pools, and volcanic hot springs, brine pools, and black organic mud totally devoid of black organic mud totally devoid of oxygen oxygen

Auto or heterotrophAuto or heterotroph cell walls lack cell walls lack

peptidoglycan peptidoglycan

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Protista Protista 

eukaryotic eukaryotic greatest variety greatest variety Most single-celled, some multiMost single-celled, some multi photosynthetic or heterotrophicphotosynthetic or heterotrophic Ex: kelp, amebas, slime mold, Ex: kelp, amebas, slime mold,

paramecium, euglenaparamecium, euglena

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Fungi Fungi  heterotrophs heterotrophs

– feed on dead or decaying feed on dead or decaying

organic matter organic matter EukaryoticEukaryotic Most multicellular, some uniMost multicellular, some uni Cell walls of chitinCell walls of chitin EX: mushroom, yeastEX: mushroom, yeast

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Plantae Plantae  multicellular multicellular photosynthetic autotrophs photosynthetic autotrophs EukaryoticEukaryotic Cells walls of cellulose Cells walls of cellulose

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Animalia Animalia 

multicellularmulticellular heterotrophic heterotrophic EukaryoticEukaryotic No cell walls No cell walls