CLASSIFICATION

Sorting into groups1. allows quick and accurate descriptions

2. simpler and precise communication3. reference system for new organisms4. enables trends to be observed and followed

5. explain relationships

How classification has changedAncient timesTwo groups, Plants and animals

criteria : basic structure, leaves, roots etc for

plants; no leaves, roots etc for animals

criteria: life and locomotion

1737 - Carl Von Linné (Linnaeus)All natural objects

(living and non-living)

MINERALSconcrete bodies without life and sensation

VEGETABLESorganised bodies with life and no sensation

ANIMALSorganised bodies with life, sensation and movementproblem: assumes all animals are mobile

and all plants are sessile

criteria: structures in cell, biochemical processes, autotrophic nature of plants known, not yet understood

1838-39 - Schleiden and Schwann

Living things(composed of cells)

PLANTCell wall, regular shape, contain chlorophyll, large vacuole etc.

ANIMALCell membrane, irregular shape, no chlorophyll

problem: some unicellular organisms had flagella, allowing movement (animal) and chloroplasts (plant)

- use of light microscope to see plant and animal

cells

criteria: structures in cell, including concept of independent cellular organisms, or dependent cells of tissues, organ etc.

1866 - Haeckel

Living things(composed of cells)

PLANTCell wall, regular shape, contain chlorophyll, large vacuole etc.

ANIMALCell membrane, irregular shape, no chlorophyll

problem: contained both autotrophic and heterotrophic unicellular

organisms in protista

- Created a kingdom for all microscopic unicellular organism

PROTISTSUnicellular organisms

criteria: structures in cell, biochemical pathways

1950’s - development of electron microscopeEUCARYOTIC

PLANTCell wall, regular shape, contain chlorophyll, large vacuole etc.

ANIMALCell membrane, irregular shape, no chlorophyll

problem: fungi are they plant, autotrophic, or animal, heterotrophic

PROCARYOTIC

PROTISTSUnicellular organisms

Pro – simpleCaryo – nucleusHave no distinct nucleus

Eu – trueCaryo – nucleusHave a distinct nucleusProcaryotes, simplest known form of life,

believe they were the first type of cell to evolve.First appeared 3050 Myr ago and where the only living things for about 5500 Myr

MONERAProcaryotic cells, no-membrane bound organelles

criteria: structures in cell and biochemical processes

1967 - R.H. WhittakerLiving things

(composed of cells)PLANTCell wall, regular shape, contain chlorophyll, large vacuole etc.

ANIMALCell membrane, irregular shape, no chlorophyll

problem: unicellular autotrophic organisms – algae- now spread across two kingdoms, saprophytic bacteria also across two kingdoms

PROTISTSUnicellular organisms

MONERAProcaryotic cells, no-membrane bound organelles

FUNGICell wall, no chloroplasts, saprophytic

1964 - amino acid sequence determines protein and this amino acid sequence is determined by the sequence of bases in DNA

This plus advances in cell biochemistry led to the discovery of two very distinct procaryotic groups.ARCHAEA BACTERIA

Murein (disaccharide-amino acid complex) not present in cell wall

Murein (disaccharide-amino acid complex) present in cell wall

Lipids in cell membrane are branched

Lipids in cell membrane are not branchedNot sensitive to

antibioticsSensitive to antibiotics

PROCARYOTES

Living things(composed of cells)

PLANTCell wall, regular shape, contain chlorophyll, large vacuole etc.

ANIMALCell membrane, irregular shape, no chlorophyll

PROTISTSUnicellular organisms

MONERAProcaryotic cells, no-membrane bound organelles, cell wall contains murein

FUNGICell wall, no chloroplasts, saprophytic

ARCHAEAprocaryotic cells, no murein in cell wall

1978 - ability to sequence DNA

1970 - six kingdoms

1990 - Carl Woese- produced a radical, new classification

system using three DOMAINS from which the major kingdoms developed

criteria:biochemical comparisons i.e. comparison of the order of particular bases for particular genes in different organisms

problem:major shift from traditional classification systems

a change occurredproducing two distinct lines

each domain shows different lineages (kingdoms) branching offby comparing structural features and using fossil records, an inference is made as to the key events in evolution

Can assist in reconstructing major events in evolution by comparing same gene from different organisms, allows the inference to be made

First form of life

Another change occurs

SELECTION CRITERIA USED IN ALL CLASSIFICATION SYSTEMS.use Keysa set of characteristics which allows

organisms to be identifiedmost common a DICHOTOMOUS KEYdivides

into two at each branch using a yes or no questionusually arranged as a flow diagram (tree) or table

(sentence)Classify 13 non-identical objectsStructural characteristics - Morphology

do not change over timetend to find in groups if one structural characteristic is common more will be e.g. Vertebral column

large number to choose fromcan show evolutionary patterns e.g. Pentadactyl limb

Biochemical techniques.1. Biochemical pathways:

• can be detected, both qualitatively and quantitatively

• as they behave in reactions as normal atoms

• use of radioactive isotopes

e.g. carbon-14 used to trace pathway of carbon through photosynthesis

2. Amino acid sequencing• proteins are made up of amino acid

units• each protein has a unique number and sequence of amino acids• by comparing amino acid sequence the more similarities would indicate a closer evolutionary relationshipe.g. cytochrome C: protein found in electron transport,

shows only one difference between man and chimpanzee

Biochemical techniques.3. DNA sequencing:

• may also allow to trace the changes occurred to create the diversity of life

• greater similarity in sequence between organisms suggests closer evolutionary relationships

• sequence of bases encodes genetic information

Why are these criteria used? • unambiguous amino acid units

• measurable

TECHNOLOGY IN CLASSIFICATION SYSTEMS

MICROSCOPESLIGHT Identification of cellular structures – living

things; plant and animals cellsELECTRON

TRANSMISSIONIdentification of organelles – procaryotes and eucaryotes

ELECTRONSCANNING

3-D structures of external structures

ELECTRONHIGH VOLTAGETRANSMISSION

Most recent, molecular level – arrangement of atoms in molecular materials

BIOCHEMICAL TECHNIQUESRADIOISOTOPES

Allows biochemical pathways to be observed- Energy source for methanogens, autotrophs etc.AMINO

ACIDSAllows comparison of complex proteins between organisms- The greater the similarity the closer the relationshipDNA Allows comparison of sequence of bases in DNA- The greater the similarity the closer the relationship

A hierarchical system assists classification.• hierarchy = a system organised into different levels

KINGDOMPHYLUMCLASSORDER FAMILYGENUS SPECIES

i.e. the levels of our current classification system are

• in classification these levels represent similarities between groups of organisms

similarity increasing between groups

numbersingroups

contains only one type of organism

contains a large number of organisms

• organisms in the same genus are more closely related than two organisms in the same family group

KINGDOMPHYLUMCLASSORDER FAMILYGENUS SPECIESBINOMIAL SYSTEM OF

NAMES

Heterotrophic, locomotionVertebrateSuckle live youngForward thumbs and eyesNo tailWalk on two legsLarge forebrain

AnimalChordateMammalsPrimateHominoidHomoSapien

• accepted system• Linnaeus system of a two word - binomial - name for all organisms

e.g. Homosapien (Homo sapien - ifwritten)

genus species• genus refers to a similar group of organisms that do not interbreed

species refers to:a group of organisms that are similar structurally, biochemically, behaviourally and are reproductively isolated producing live, fertile young

– BASIC UNIT OF CLASSIFICATIONA

horseA donkey

An AssInfertile

A tiger

A Lion

A LigerInfertile

Very closely related but not from same speciesMore modern definitions of species includes number and shape of chromosomes

Advantages of scientific naming

e.g. prickly Moses2. removes common name variation1. universal language

Western Australia for Acacia pulchellaNew South Wales

for Acacia ulicifolia

Vic and Tas Acacia verticillata

e.g. Macropus genus kangaroo3. can indicate degree of relatedness

species giganteus (eastern grey)

rufus (red)

fulginosus (western grey)

show similar morphology, physiology, biochemistry and phylogeny (evolution) which is reflected in their scientific name4. removes misleading common names eg

cuttlefish are not fish but molluscs