Chapter 18:Classification

18-1: History of Taxonomy

Early Systems of Classification• Taxonomy: branch of biology that names and

groups organisms according to their characteristics and evolutionary history

Aristotle

• 2,000 years ago–Plants: three categories based on their

stems–Animals: based

on where they live• Land•Water• Air

Problems

• Scientific exploration discover MANY new species

• Common name did not describe actual animal– Ex: Jellyfish: NOT a fish

• Common names varied by location

Linnaeus’ System

• Swedish naturalist, Carolus Linnaeus, (1707-78)• Used organisms morphology to categorize it– Form and structure

Levels of Classification• Kingdom• Phylum• Class • Order• Family• Genus• Species Kings Play Chess On Funny Green Squares

Binomial Nomenclature • Species name has two

parts:–Genus– Species identifier:

descriptive word• Ex: Homo sapien–Homo is the

genus–sapien means

“wise”

Further Naming and Classifying• Botanists (plants)

further classify• Varieties: subset of

species• Subspecies: zoologists

refer to species that occur in different geographic locations

• Phylogeny: evolutionary history

18-2: Modern Phylogenetic Taxonomy• Past: – Morphology

• Preset:– Morphology– Chromosomal

characteristics– Nucleotide and

amino acid sequences

– Embryonic development

Systematics• Organizes tremendous diversity of living things

in the context of evolution• Phylogenetic tree: a family tree that shows

the evolutionary relationships thought to exist among groups of organisms– Represents a hypothesis– Based on multiple lines

of evidence – Subject to change

The Fossil Record

• Often provides clues to evolutionary relationships

• HOWEVER:– Some fossil records

very complete (ocean-living invertebrates) others are missing large portions

Morphology• Compare

morphology of organism to morphology of other living things

• Homologous features show descent from common ancestors

Embryonic Patterns of Development • Early on in

development most living things look very similar

• As they develop it is easier to see how their morphology differs

Chromosomes and Macromolecules• DNA, RNA, and proteins• Number of amino acid differences is a clue to

how long ago two species diverged from a shared ancestor

• Problem: ASSUMES all changes to sequence occur at random and NOT natural selection

Karyotype

• Some similar bands on chromosomes, more related two organisms are

Cladistics• Uses shared derived characters of organisms

to establish evolutionary relationships• Derived characters: feature that apparently

evolved only within the group under consideration

• Cladograms: ancestry diagrams made by means of cladistical analysis

18-3:Two Modern Systems of Classification

Six-Kingdom System

• Archaebacteria• Eubacteria• Protista• Fungi• Plantae• Animalia

Kingdom Archaebacteria

• Unicellular prokaryotes• Distinctive cell membrane• Autotrophs:

chemiosmosis (use elements/chemicals for energy)

• Many live in very harsh environments– Hot spring– VERY salty water– Anaerobic environments (No air)

• Archae- in Greek means “ancient”

• FIRST organisms on Earth• Reproduce: Binary fission• Nutrition: Autotrophs and

heterotrophs

Kingdom Eubacteria• Unicellular prokaryotes• Eu- means “true”• Most bacteria that

affect your life – Tooth decay– Milk yogurt– Food poisoning

• Reproduce: Binary fission• Nutrition: Autotrophs and heterotrophs

Kingdom Protista• Eukaryotic and prokaryotic• Difficult to describe• All eukaryotes that are

not fungi, plants, or animals• Reproduction: sexual cycles

unknown but they do exchange genetic info

• Nutrition: Autotrophs AND heterotrophs– Euglena can photosynthesize– Amoeba eats other organisms

Kingdom Fungi• Unicellular and multicellular eukaryotes• Reproduction: sexual cycles unknown but they

do exchange genetic info• Nutrition: Heterotrophs; Absorb nutrients• Ex: puffballs, mushrooms,

rusts, molds

Kingdom Plantae

• Multicellular plants• Reproduction: most have

sexual cycle based on meiosis

• Nutrition: All but a few are heterotrophic

Kingdom Animalia

• Multicellular• Eukaryotic• Reproduction: Sexual by means

of meiosis forming gametes• Nutrition: Heterotrophs• Most have body symmetry and

move about environment

Three-Domain System

• In 1977, molecular biologist, Carl Woese• Classified by comparing ribosomal RNA• Why? All organisms have ribosomes so we can

look at every living thing’s rRNA and compare it with others

• Three main domains:– Domain Archae– Domain Bacteria– Domain Eukarya

Domain Archae

• Same as the kingdom Archaebacteria (in six kingdom system)

Domain Bacteria

• Same as kingdom Eubacteria

Domain Eukarya

• Protists, fungi, plants, and animals• Have nuclei with linear chromosomes and

membrane bound organelles