Public Domain

The

Cha

in o

f Bei

ng a

nd a

New

Tax

onom

y

In th

e 17

00s,

Cha

rles B

onne

t, a

Swiss

nat

ural

ist

who

stud

ied

plan

ts a

nd a

nim

als,

org

anize

d th

e na

tura

l wor

ld in

a la

dder

-like

hie

rarc

hy th

at

refle

cted

com

mon

thou

ght a

t the

tim

e.

Bonn

et b

elie

ved

that

a d

ivin

e Be

ing

crea

ted

mat

eria

ls th

at p

rogr

esse

d by

thei

r ow

n fo

rce

into

incr

easin

gly

com

plex

stag

es o

f exi

sten

ce.

Writt

en in

Fre

nch,

his

1745

illu

stra

tion

of th

e Ch

ain

of B

eing

(sho

wn

to th

e rig

ht) l

ists s

ever

al

stag

es o

f exi

sten

ce: fi

re, a

ir, w

ater

, lan

d, su

lfur,

met

als,

salts

, sto

nes,

pla

nts,

inse

cts,

shel

ls,

serp

ents

, fish

, fow

l, qu

adru

peds

, and

hum

ans.

How

ever

, oth

er e

arly

scie

ntist

s in

the

mid

17

00s w

ere

orga

nizin

g lif

e in

a w

ay th

at w

as

base

d so

lely

on

obse

rvab

le tr

aits

rath

er

than

phi

loso

phy.

The

y w

ere

conc

erne

d w

ith

crea

ting

a ne

w ta

xono

my,

or th

e de

finin

g an

d na

min

g of

gro

ups o

f org

anism

s bas

ed o

n sh

ared

cha

ract

eristi

cs.

Imag

ine

that

you

are

a b

iolo

gist

in 1

735

who

ado

pts t

his n

ew ta

xono

my.

The

car

ds

repr

esen

t the

type

s of o

rgan

isms y

ou c

ould

ha

ve o

bser

ved

at th

e tim

e. H

ow w

ould

you

gr

oup

thes

e or

gani

sms?

Use

the

card

s to

deve

lop

a ta

xono

mic

mod

el th

at o

rgan

izes

thes

e liv

ing

thin

gs.

Leeu

wen

hoek

’s “A

nim

alcu

les”

In 1

674,

Ant

onie

van

Lee

uwen

hoek

sent

to th

e Ro

yal S

ocie

ty o

f Lo

ndon

the

first

eve

r obs

erva

tions

of m

icro

scop

ic si

ngle

-cel

led

orga

nism

s. In

one

of h

is m

any

lette

rs, h

e w

rote

abo

ut th

e pl

aque

be

twee

n pe

ople

s’ te

eth:

“I th

en m

ost a

lway

s saw

, with

gre

at

won

der,

that

in th

e sa

id m

atter

th

ere

wer

e m

any

very

litt

le li

ving

an

imal

cule

s, v

ery

pretti

ly a

-mov

ing.

Th

e bi

gges

t sor

t…ha

d a

very

stro

ng

and

swift

moti

on, a

nd sh

ot th

roug

h th

e w

ater

(or s

pitt

le) l

ike

a pi

ke d

oes

thro

ugh

the

wat

er. T

he se

cond

sort

…oft

-tim

es sp

un ro

und

like

a to

p.”

Thou

gh h

is ill

ustr

ation

s (su

ch a

s the

imag

e ab

ove)

and

find

ings

w

ere

initi

ally

met

with

skep

ticism

, fur

ther

inve

stiga

tion

by

othe

r sci

entis

ts sh

owed

that

mic

roor

gani

sms d

id, i

n fa

ct, e

xist

. Su

bseq

uent

adv

ance

men

ts in

tech

nolo

gy m

ade

the

mic

rosc

ope

a co

mm

on a

nd v

alua

ble

scie

ntific

tool

.

In 1

859,

Cha

rles D

arw

in p

ublis

hed

The

Orig

in o

f Spe

cies

, whi

ch

prov

ed to

be

very

pop

ular

, tho

ugh

cont

rove

rsia

l at t

he ti

me.

Th

e bo

ok c

onta

ined

one

of t

he fi

rst a

rgum

ents

for t

he th

eory

of

evo

lutio

n w

hich

was

bac

ked

by e

vide

nce

and

prop

osed

a

mec

hani

sm fo

r the

des

cent

of a

ll liv

ing

thin

gs fr

om a

com

mon

an

cest

or.

Eval

uate

you

r pre

viou

s mod

el o

f the

tree

of l

ife

in li

ght o

f the

two

new

pie

ces o

f inf

orm

ation

: 1)

the

exist

ence

of m

icro

orga

nism

s and

2)

the

theo

ry o

f evo

lutio

n.

Can

your

mod

el e

xpla

in th

is ne

w in

form

ation

? U

se th

e ca

rds t

o re

vise

you

r mod

el a

s nec

essa

ry.

1866

A17

58 A

Public Domain

Phot

o: A

mod

el o

f an

early

mic

rosc

ope

used

by

Leeu

wen

hoek

to

mak

e th

e fir

st o

bser

vatio

ns o

f mic

roor

gani

sms..

(CC BY-SA 3.0) Jeroen Rouwkema

Édou

ard

Cha

tton

and

Prok

aryo

tes

As m

icro

scop

e te

chno

logy

impr

oved

, mor

e sc

ienti

sts s

tudi

ed

cells

and

disc

over

ed n

ew sp

ecie

s of m

icro

bes.

In 1

938,

the

Fren

ch b

iolo

gist

Édo

uard

Cha

tton

was

the

first

to c

hara

cter

ize

cells

as b

eing

with

a n

ucle

us (e

ukar

yotic

) or w

ithou

t a n

ucle

us

(pro

kary

otic)

. Ove

r the

nex

t sev

eral

yea

rs, f

urth

er in

vesti

gatio

ns

by sc

ienti

sts p

opul

arize

d Ch

atton

’s w

ork

and

defin

ed m

ore

diffe

renc

es b

etw

een

euka

ryot

es a

nd p

roka

ryot

es. T

he ta

ble

belo

w

indi

cate

s whe

ther

eac

h or

gani

sm is

a p

roka

ryot

e or

euk

aryo

te.

Revi

se y

our p

revi

ous m

odel

of t

he tr

ee o

f life

to 1

) refl

ect t

his n

ew

piec

e of

info

rmati

on a

bout

pro

kary

otic

and

euka

ryoti

c ce

lls a

nd 2

) in

corp

orat

e th

e ne

wly

disc

over

ed o

rgan

isms.

Prok

aryo

tes

(cel

ls w

ithou

t nuc

leus

)Eu

kary

otes

(cel

ls w

ith n

ucle

us)

Arc

haeo

glob

us fu

lgid

usA

cino

nyx

juba

tus

Bact

eroi

dete

s sp

p.A

garic

us b

ispo

rus

Begg

iato

a sp

p.Ba

cilla

rioph

ycea

e (c

lass

)

Borr

elia

bur

gdor

feri

Cup

ress

ocyp

aris

leyl

andi

i

Clo

strid

ium

diffi

cile

Dic

kson

ia a

ntar

ctic

a

Cya

noba

cter

ia s

pp.

Dig

itaria

eria

ntha

Des

ulfo

vibr

io d

esul

furic

ans

Equu

s qu

agga

Ente

roco

ccus

spp

.Eu

dorc

as th

omso

nii

Geo

bact

er m

etal

lired

ucen

sG

iard

ia in

testi

nalis

Hal

ofer

ax v

olca

nii

Gyp

s af

rican

us

Hal

oqua

drat

um w

alsb

yiH

omo

sapi

ens

Lact

obac

illus

spp

.Lir

iode

ndro

n tu

lipife

ra

Met

hano

brev

ibac

ter s

mith

iiPa

nthe

ra le

o

Met

hano

sarc

ina

acet

ivor

ans

Para

mec

ium

aur

elia

Met

hylo

cocc

us s

pp.

Pyru

s co

mm

unis

Rhod

opse

udon

omas

spp

.Sa

ccha

rom

yces

cer

evis

iae

Sulfo

lobu

s is

land

icus

Thio

baci

llus

spp.

Trep

onem

a pa

llidu

m

Vibr

io s

pp.

The

Dis

cove

ry o

f Arc

haea

In th

e 19

70s,

adv

ance

s in

scie

nce

and

tech

nolo

gy a

llow

ed

scie

ntist

s to

exam

ine

gene

tic in

form

ation

foun

d in

DN

A or

RN

A to

de

term

ine

the

rela

tions

hips

bet

wee

n sp

ecie

s. U

sing

the

reas

onin

g th

at g

roup

s of o

rgan

isms w

ith a

lot o

f gen

etic

info

rmati

on in

co

mm

on a

re m

ore

clos

ely

rela

ted

to e

ach

othe

r tha

n ot

hers

that

ha

ve le

ss in

com

mon

, sci

entis

ts b

egan

to re

orga

nize

the

tree

of

life.

Usin

g th

e sim

ulat

ed D

NA

sequ

ence

s det

erm

ine

how

the

orga

nism

s ar

e re

late

d. O

bser

ve h

ow th

is ne

w in

form

ation

influ

ence

s the

tree

of

life

mod

el.

1969

A19

90 A

1758 B

AnimalsAnimals PlantsPlants

© P

roje

ct N

EURO

N, U

nive

rsity

of I

llino

is

Illustrated interpretation of Linnaeus’ model18

66 B

Ani

mal

sPr

otis

ts

Monera

Plan

ts

© P

roje

ct N

EURO

N, U

nive

rsity

of I

llino

is

Illus

trate

d in

terp

reta

tion

of H

aeck

el’s

mod

el

1969

B

Prot

ists

Mon

era

Plan

tsFu

ngi

Ani

mal

s

Euka

ryot

es

Prok

aryo

tes

© Project NEURON, University of Illinois

Illus

trate

d in

terp

reta

tion

of W

hitta

ker’s

mod

el

ArchaeaBa

cter

ia

OriginOrigin

Eukaryotes

AnimalsFungi Plants Protists

© P

roje

ct N

EURO

N, U

nive

rsity

of I

llino

is

Illustrated interpretation of Woese’s model1990 B

Publ

ic D

omai

nPu

blic

Dom

ain

Publ

ic D

omai

n

Carolus Linnaeus’ Systema Naturae

Carl Linnaeus is the founder of modern taxonomy, the naming and classification of life forms. He started using two-part names for living things, a method that is still used today. For example, he used the genus and species name of Panthera leo for the lion.

Linnaeus’ interests in biology originated with plants. Growing up, his father would show Linnaeus flowers in the garden and tell him their names. As an adult, Linnaeus continued to study plants and animals on expeditions across Europe before publishing his work in several books.

In his book Systema Naturae (Latin for “The Systems of Nature”), Linnaeus classified over 12,000 plants and animals. During his lifetime, the contents were constantly being updated and revised based on new knowledge. For instance, whales were originally classified as fish in the first edition (1735), but in the tenth and definitive edition (1758), they were reclassified as mammals.

Linnaeus arranged life into two main categories, called “kingdoms”: plants and animals. Plants were grouped into 24 classes based on their reproductive structures and included “true” plants as well as fungi, algae, and lichen. His classification of animals included subgroups of mammals, birds, amphibians, fish, insects, and “vermes,” or all other invertebrates that were not insects, such as worms, slugs and clams.

Below is a table from an earlier edition of Systema Naturae showing some groups from the kingdom “Animale.” Do you recognize any of the organism names?

1758 B

Public Domain

Public Domain

Erns

t Hae

ckel

Erns

t Hae

ckel

was

form

ally

trai

ned

as a

med

ical

doc

tor b

efor

e be

com

ing

a zo

olog

ist. D

urin

g hi

s life

, inc

ludi

ng th

e tim

e he

was

a p

rofe

ssor

at t

he

Uni

vers

ity o

f Jen

a, G

erm

any,

he st

udie

d m

any

inve

rteb

rate

gro

ups s

uch

as sp

onge

s and

radi

olar

ians

, tiny

zoop

lank

ton

with

min

eral

skel

eton

s.

Haec

kel w

as a

n ac

com

plish

ed il

lust

rato

r and

mad

e ex

tens

ive

jour

neys

ar

ound

the

wor

ld, n

amin

g th

ousa

nds o

f new

spec

ies i

n hi

s life

time.

Haec

kel’s

con

trib

ution

s to

the

disc

over

y of

new

spec

ies a

nd th

e or

gani

zatio

n of

life

pro

ved

influ

entia

l. In

his

book

Gen

erel

le M

orph

olog

ie

der O

rgan

ismen

(Ger

man

for “

Gene

ral m

orph

olog

y of

org

anism

s”)

publ

ished

in 1

866,

Hae

ckel

dep

icte

d a

tree

(see

illu

stra

tion)

with

thre

e ki

ngdo

ms:

Pla

ntae

, Ani

mal

ia, a

nd P

rotis

ta. A

t the

tim

e, P

rotis

ta in

clud

ed

all m

icro

scop

ic o

rgan

isms.

At t

he o

rigin

of t

he tr

ee h

e pu

t “M

oner

es”

or M

oner

a, a

gro

up o

f sim

ple

mic

robe

s poo

rly u

nder

stoo

d at

the

time.

Hae

ckel

thou

ght t

hese

org

anism

s wer

e sim

ilar t

o th

e fir

st li

ving

or

gani

sms f

rom

whi

ch

all l

ife e

volv

ed.

1866

B

Whi

ttake

r, R.

H. (

1969

)©

Nat

iona

l Aca

dem

y of

Sci

ence

s.

Robert H. Whittaker

In 1969, Robert Whittaker published a scientific paper in which he proposed a new five-kingdom model of the tree of life. In his model, Whittaker incorporated work of Chatton and other scientists who distinguished prokaryotes from eukaryotes. He also established a new kingdom for fungi, which had mostly been grouped with plants in the past. The separation of fungi was mostly based on the evidence that fungi consume decaying or dead matter whereas plants produce their own food.

In Whittaker’s model (shown below), there were five kingdoms: Monera (prokaryotic organisms), Protista (eukaryotic unicellular organisms), Plantae, Animalia, and Fungi (all eukaryotic multicellular organisms). As seen in his illustration, the arrangement suggested that some kingdoms, such as Monera and Protista, contained present-day species as well as the ancestors of other kingdoms. The arrows in the bottom right also indicate how he organized species based on whether they photosynthesize, absorb, or ingest food.

1969 B

Woe

se, C

.R.,

Kan

dler

, O. &

Whe

elis,

M.L

. (19

90)

Carl Woese

Carl Woese, a scientist at the University of Illinois, was one of the first to use molecular data to investigate the evolutionary relationships of organisms. The illustration below is from a 1990 publication he wrote with colleagues, titled “Towards a natural system of organisms: Proposal for domains Archaea, Bacteria, and Eucarya.” A “domain” is a taxonomic group even larger than a kingdom. There were now six kingdoms in the new model, revised from Whittaker’s five kingdom model. The Plantae, Animalia, Protista, and Fungi kingdoms were grouped in the Eukarya domain, and the Bacteria and Archaea domains contained the Bacteria and Archaea kingdoms, respectively.

In previous models of the tree of life, archaea had been classified with bacteria, and both under the category of monera. Although archaea are visually similar to bacteria, studies indicate that archaea have genes and cellular functions more similar to eukaryotes. The earliest discovered archaea were in extreme environments such as volcanic hot springs and salt lakes, but since then they have also been found in places such as soils and human intestines. Archaea species derive energy from compounds ranging from sugars to metal ions, and they have unique components in their cell membranes not found in the other domains.

1990 B

© 2

004

Don

Ham

erm

an, U

nive

rsity

of I

llino

is