classification of living things chapter 20. classification of living things 2outlinetaxonomy ...

Classification of Living Things

Chapter 20

2Classification ofClassification of Living Things Living Things

OutlineOutline

TaxonomyTaxonomy Binomial SystemBinomial System Species IdentificationSpecies Identification Classification CategoriesClassification Categories

Phylogenetic TreesPhylogenetic Trees SystematicsSystematics Taxonomy (naming of organisms)Taxonomy (naming of organisms) Classification (placing species in the proper categories)Classification (placing species in the proper categories)

Systematics TodaySystematics Today Cladistic SystematicsCladistic Systematics Phenetic SystematicsPhenetic Systematics

Classification SystemsClassification Systems The Five Kingdom SystemThe Five Kingdom System The Three Domain SsytemThe Three Domain Ssytem


TaxonomyTaxonomy

Branch of biology concerned with identifying, Branch of biology concerned with identifying, naming, and classifying organismsnaming, and classifying organisms

Began with the ancient Greeks and RomansBegan with the ancient Greeks and RomansAristotle classified organisms into groups Aristotle classified organisms into groups such as horses, birds, and oakssuch as horses, birds, and oaks

John Ray (1627–1705)John Ray (1627–1705)Believed that each organism should have a Believed that each organism should have a set nameset name

Otherwise, “men…cannot see and record Otherwise, “men…cannot see and record accurately.”accurately.”

4Classifying Organisms

5Classification ofClassification of Living Things Living ThingsTaxonomy:Taxonomy:

Binomial SystemBinomial System

Mid-eighteenth century, Linnaeus developed Mid-eighteenth century, Linnaeus developed the binomial system of nomenclaturethe binomial system of nomenclature

First word is genus nameFirst word is genus name

Second word is specific epithetSecond word is specific epithet

Refers to one species (of potentially many) Refers to one species (of potentially many) within its genuswithin its genus

A species is referred to by the full binomial A species is referred to by the full binomial name (Genus species)name (Genus species)

Genus name can be used alone to refer to a Genus name can be used alone to refer to a group of related speciesgroup of related species

6Classification ofClassification of Living Things Living ThingsTaxonomy:Taxonomy:

Distinguishing SpeciesDistinguishing Species

Distinguishing species on the basis of Distinguishing species on the basis of structure can be difficultstructure can be difficultMembers of the same species can vary in Members of the same species can vary in structurestructure

Attempts to demonstrate reproductive Attempts to demonstrate reproductive isolation is problematic because:isolation is problematic because:

Some species hybridize, andSome species hybridize, and

Reproductive isolation is difficult to observeReproductive isolation is difficult to observe

7Hybridization between speciesZebroids are horse-zebra

hybrids.


Classification CategoriesClassification Categories

Modern taxonomists use the following Modern taxonomists use the following classification:classification:SpeciesSpeciesGenus – one or more speciesGenus – one or more speciesFamily – one or more generaFamily – one or more generaOrder – one or more familiesOrder – one or more familiesClass – one or more ordersClass – one or more ordersPhylum – one or more classesPhylum – one or more classesKingdom – one or more phylaKingdom – one or more phylaDomain – one or more kingdomsDomain – one or more kingdoms


Eukarya- membrane-bounded nucleusEukarya- membrane-bounded nucleus

Animalia- motile, multicellular, internal cavity for Animalia- motile, multicellular, internal cavity for digestion of nutrientsdigestion of nutrients

Chordata- organisms that at one time have a dorsal Chordata- organisms that at one time have a dorsal hollow nerve cord, a notochord, pharyngeal hollow nerve cord, a notochord, pharyngeal pouches, and a postanal tailpouches, and a postanal tail

Mammalia- warm-blooded vertebrates with Mammalia- warm-blooded vertebrates with mammary glands; body with hair; mammary glands; body with hair;

Primates- well-developed brain opposable thumb Primates- well-developed brain opposable thumb

Hominidae- upright stance and bipedal locomotionHominidae- upright stance and bipedal locomotion

Homo- Full brain development, hand anatomy for Homo- Full brain development, hand anatomy for making toolsmaking tools

Species- sapiens modern humans; speech centersSpecies- sapiens modern humans; speech centers


Classification CategoriesClassification Categories

The higher the category, the The higher the category, the more inclusivemore inclusive

Organisms in the same domain have general Organisms in the same domain have general characteristics in commoncharacteristics in common

In most cases, classification categories can In most cases, classification categories can be subdivided into additional categoriesbe subdivided into additional categories

SuperorderSuperorder

OrderOrder

SuborderSuborder

InfraorderInfraorder


Phylogenetic TreesPhylogenetic Trees

Systematics - the diversity of organisms at all Systematics - the diversity of organisms at all levelslevels

One goal of systematics is to determine One goal of systematics is to determine phylogeny (phylogeny (evolutionary historyevolutionary history) of a group) of a group

Phylogeny often represented as a Phylogeny often represented as a phylogenetic treephylogenetic treeA diagram indicating lines of descentA diagram indicating lines of descentEach branching point:Each branching point: Is a divergence from a common ancestorIs a divergence from a common ancestor

Represents an organism that gives rise to two Represents an organism that gives rise to two new groupsnew groups


Phylogenetic TreesPhylogenetic Trees

Classification lists the unique characters of Classification lists the unique characters of each taxon and is intended to reflect each taxon and is intended to reflect phylogenyphylogeny

Primitive characters:Primitive characters:

Present in all members of a group, andPresent in all members of a group, and

Present in the common ancestorPresent in the common ancestor

Derived characters:Derived characters:

Present in some members of a group, butPresent in some members of a group, but

Absent in the common ancestorAbsent in the common ancestor

13Classification ofClassification of Living Things Living ThingsTracing PhylogenyTracing Phylogeny

Fossil RecordFossil Record Fossil record is incompleteFossil record is incomplete

It is often difficult to determine the phylogeny of a It is often difficult to determine the phylogeny of a fossilfossil

HomologyHomology Refers to features that stem from a common ancestorRefers to features that stem from a common ancestor

Homologous structures are related to each other Homologous structures are related to each other through common descentthrough common descent

Analogy-wings of an insect and the wings of a bat Analogy-wings of an insect and the wings of a bat are analogousare analogous Similarity due to convergence-similar characters in Similarity due to convergence-similar characters in

distantly related lines of descent.distantly related lines of descent.

14Ancestral Angiosperm


Tracing PhylogenyTracing Phylogeny

Convergent EvolutionConvergent Evolution

The acquisition of a feature in distantly related The acquisition of a feature in distantly related lines of descentlines of descent

The feature is not present in a common The feature is not present in a common ancestorancestor

Parallel EvolutionParallel Evolution

The acquisition of a feature in two or more The acquisition of a feature in two or more related lineagesrelated lineages

The feature is not present in a common The feature is not present in a common ancestorancestor

16Convergent Evolution-both like dry, hot environments & succulent with spiny

leavesbut not closely related.


Molecular DataMolecular Data

Protein ComparisonsProtein Comparisons Immunological techniquesImmunological techniques Degree of cross reaction used to judge relationshipDegree of cross reaction used to judge relationship

Amino acid sequencingAmino acid sequencing Similar sequence in same protein indicates close Similar sequence in same protein indicates close

relationshiprelationshipRNA and DNA ComparisonsRNA and DNA Comparisons

Systematics assumes:Systematics assumes: Two species with similar base-pair sequences are Two species with similar base-pair sequences are

assumed to be closely relatedassumed to be closely related Two species with differing base-pair sequences are Two species with differing base-pair sequences are

assumed to be only distantly relatedassumed to be only distantly relatedMolecular ClocksMolecular Clocks

Use non adaptive nucleotide sequencesUse non adaptive nucleotide sequences Assumed constant rate of mutation over timeAssumed constant rate of mutation over time

18Ancestry of Giant Pandas


Cladistic SystematicsCladistic Systematics

Traces evolutionary history of the group Traces evolutionary history of the group under studyunder study

Uses shared derived characters to:Uses shared derived characters to:

Classify organisms, andClassify organisms, and

Arrange taxa into a cladogramArrange taxa into a cladogram

A cladogram is a special type of phylogenetic A cladogram is a special type of phylogenetic treetree

A clade is an evolutionary branch that includes:A clade is an evolutionary branch that includes: A common ancestor, together withA common ancestor, together with

All its descendent speciesAll its descendent species

20Constructing a Cladogram


ParsimonyParsimony

Cladists are always guided by the principle of Cladists are always guided by the principle of parsimonyparsimony

The arrangement requiring the fewest The arrangement requiring the fewest assumptions is preferredassumptions is preferred

This would:This would:

Leave the fewest number of shared derived Leave the fewest number of shared derived characters unexplainedcharacters unexplained

Minimize the number of assumed evolutionary Minimize the number of assumed evolutionary changeschanges

The reliability of a cladogram is dependent on The reliability of a cladogram is dependent on the knowledge and skill of the investigatorthe knowledge and skill of the investigator

22Cladistic Versus Traditional View ofReptilian Phylogeny


Phenetic SystematicsPhenetic Systematics

Assumes it will never be possible to construct Assumes it will never be possible to construct a truly phylogenetic classification systema truly phylogenetic classification system

Species are classified according to the total Species are classified according to the total number of shared similaritiesnumber of shared similarities

Disregards assumed phylogenetic Disregards assumed phylogenetic considerationsconsiderations

Ignores issues of convergent or parallel Ignores issues of convergent or parallel evolutionevolution


Traditional SystematicsTraditional Systematics

Mainly uses anatomical dataMainly uses anatomical data

Classify organisms using assumed phylogeny Classify organisms using assumed phylogeny with emphasis on phenotypewith emphasis on phenotype

Stress both common ancestry and degree of Stress both common ancestry and degree of structural difference among divergent groupsstructural difference among divergent groups

Construct phylogenetic trees by applying Construct phylogenetic trees by applying evolutionary principles to categoriesevolutionary principles to categories

Not strict in making sure all taxa are Not strict in making sure all taxa are monophyleticmonophyletic


Classification SystemsClassification Systems

Until the middle of the twentieth century, Until the middle of the twentieth century, biologists recognized only two kingdomsbiologists recognized only two kingdoms

Plantae (plants)Plantae (plants)

Animalia (animals)Animalia (animals)

Protista (protists) were added as third Protista (protists) were added as third kingdom in the 1880skingdom in the 1880s

Whittaker expanded to five kingdoms in 1969 Whittaker expanded to five kingdoms in 1969 by adding Fungi and Moneraby adding Fungi and Monera

26Classification ofClassification of Living Things Living ThingsThree-Domain System-compare table Three-Domain System-compare table

20.320.3

The Bacteria and Archaea are so different The Bacteria and Archaea are so different they have been assigned to separate they have been assigned to separate domains domains

Similar in that both are asexually reproducing Similar in that both are asexually reproducing unicellular prokaryotesunicellular prokaryotes

Distinguishable by:Distinguishable by:

Difference in rRNA base sequencesDifference in rRNA base sequences

Plasma membrane chemistryPlasma membrane chemistry

Cell wall chemistryCell wall chemistry


Three-Domain SystemThree-Domain System

Domain EukaryaDomain Eukarya

Unicellular and multicellular organisms Unicellular and multicellular organisms

Cells with a membrane-bounded nucleusCells with a membrane-bounded nucleus

Sexual reproduction commonSexual reproduction common

Contains four kingdomsContains four kingdoms

Kingdom Protista

Kingdom Fungi

Kingdom Plantae

Kingdom Animalia

28The Three-DomainSystem of

Classification

29The Three Domains of Life


ReviewReview

TaxonomyTaxonomy Binomial SystemBinomial System Species IdentificationSpecies Identification Classification CategoriesClassification Categories

Phylogenetic TreesPhylogenetic Trees SystematicsSystematics Taxonomy (naming of organisms)Taxonomy (naming of organisms) Classification (placing species in the proper categories)Classification (placing species in the proper categories)

Systematics TodaySystematics Today Cladistic SystematicsCladistic Systematics Phenetic SystematicsPhenetic Systematics

Classification SystemsClassification Systems The Five Kingdom SystemThe Five Kingdom System The Three Domain SystemThe Three Domain System

Classification of Living Things

Ending Slide Chapter 20

classification of living things chapter 20. classification of living things 2outlinetaxonomy ...

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following classification

genus species genus

species zebroids

species family

group of related species

domain ssytem slide

classifying organisms

proper categories systematics