4.1

Protozoa

Metazoa

4.2

Fertilized egg

Two-cell stage(cleavage begins)

Four-cell stage

Eight-cell stage

Radial Cleavage Spiral Cleavage

4.3

Cnidaria: Aurelia

Annelida: Eupomatus

Cephalochordata: Brachiostoma

4.4

1 2 3 4 5 6 7 8 9 10 11 12 13

Anterior Medial Posterior

a-1 a-13

b-1 b-9

c-4 c-13

d-1 d-13

Vertebrates

1 10Branchiostoma floridae(Chordata)

lab pb Dfd SerAntpUbx AbdA

AbdB

Drosophila melanogaster(Arthropoda)

Drosophila pseudoobscura(Arthropoda)

mxp Dfd Cx Ptl Utx A Extra urogomphiTribolium castaneum(Arthropoda)

AfDfdAfSer

AfAntpAfUbx

AfabdAArtemia(Arthropoda)

1 8Ctenodrilus serratus(Annelida)

lin-39(ceg-15)

egl-5(ceg-11)

ceh-13 mab-5Caenorhabditis elegans(Nemertina)

lab ?pb Dfd AntpSchistosoma mansoni(Platyhelminthes)

Cnox1 Cnox2 antpCChlorohydra viridissima(Cnidaria)

4.5

Fruit fly Ubx(Insect)

Mouse Ubx(Mammal)

C. elegans Ubx(Nematoda)

Leech Ubx(Annelid)

Amphioxus pb(Urochordate)

Frog AbdB(Amphibian)

old

emslab pb Dfd Scr Ubx AbdB eve

The Zootype

4.6

Strain: Ork

0

20

40

60

80

100

120

140

0 2 4 6 8

Added Salt (%)

Perc

enta

ge S

urvi

val

Area

of A

nal P

apilla

e

Strain: sp2bs2

0

20

40

60

80

100

120

140

0 2 4 6 8

Added Salt (%)

Strain: al b c sp2

0

20

40

60

80

100

120

140

0 2 4 6 8

Added Salt (%)

4.7

2.00

1.75

1.50

1.25

1.00

0.75

1973

1983

1993

Year 2003 0.

2 0.1 0.0

-0.1 -0.2

Plasticity

Fitn

ess

4.8

Original phenotypes

Phenotypicchanges

Changes inStructural genes

New environments

are entered

Natural selection acts on new

phenotypic traits

Changes in diet, daily patterns of activity, social interactions, etc.

Reproductive isolation

4.9

HETEROCHRONY

Different morphologyDifferent body size

Same morphologyDifferent body size

Peramorphosis

D develops new stages not present

in A.

Paedomorphosis

D adult similar to juvenile A.

Predisplacement

Onset of developmentoccurs earlier in D,

relative to A.

Acceleration

Juvenile developmentis accelerated in D,

relative to A.

Peramorphosis

D develops new stages not present

in A.

Postdisplacement

Onset of developmentis delayed in D,

relative to A.

Neoteny

Juvenile development is retarded in D,

relative to A.

Progenesis

Sexual maturity occurs earlier in D than in A.

Gigantism

D larger than A in body size.

Dwarfism

D smaller than A in body size.

4.10

(a) (b)

4.11

A B C

Fertilization Sexual maturity

B C DPredisplacement

A B C

A B C

AAcceleration

HypermorphosisA B C D

A B C

Fertilization Sexual maturity

A BPostdisplacement

A B C

Neoteny

A B

A B C

Progenesis

A B

(b) Peramorphosis(a) Paedomorphosis

Descendant

Descendant

Descendant

Ancestor

Ancestor

Ancestor

B C D

4.12

Hor

n Le

ngth

(mm

)

Basilar Length of Skull (mm)

600

400

200

100

60

40

20

10 8 6

4

400 1000

4.13

• Early response to external stimuli• Delayed sensitive period for socialization

Behavior

• Early sexual maturation• Longer breeding season• Larger litter size

Physiology

• Floppy ears• Shorter or rolled tail• Short legs• Depigmentation

Morphology

Artificial selection target

HormonesNeurotransmitters

Tamability

Developmental program (simplified)

Genes

Correlated changes

4.14

Atta

ck F

requ

ency

S1

S4

S13

20

30

10

0

20

30

10

0

20

30

10

0

40 80 160 180 220 260Age (Days)

4.15

(a) (b)

(c) (d)

(e)

4.16

Telencephalon

Procencephalon Diencephalon

Mesencephalon

Rhombencephalon

A4 A3 A2 A1

Hox A Genes

4.17

(a) (b)

4.18

Pairs of littermates

Weaned at about 21-24 days of age

Randomly assigned

Enriched environment

Impoverished environment

Treatment duration(e.g., 30 days)

Behavioraltesting

Chemical and morphological

analyses of the CNS