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

4.5 Fruit fly Ubx (Insect) Mouse Ubx (Mammal) C. elegans Ubx (Nematoda) Leech Ubx (Annelid) Amphioxus pb (Urochordate) Frog AbdB (Amphibian) old ems labpbDfdScrUbxAbdBeve The Zootype

4.6

Year Plasticity Fitness

4.8 Original phenotypes Phenotypic changes Changes in Structural 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 morphology Different body size Same morphology Different body size Peramorphosis D develops new stages not present in A. Paedomorphosis D adult similar to juvenile A. Predisplacement Onset of development occurs earlier in D, relative to A. Acceleration Juvenile development is accelerated in D, relative to A. Peramorphosis D develops new stages not present in A. Postdisplacement Onset of development is 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 ABC FertilizationSexual maturity BCD Predisplacement ABC ABC A Acceleration Hypermorphosis ABCD ABC FertilizationSexual maturity AB Postdisplacement ABC Neoteny AB ABC Progenesis AB (b) Peramorphosis (a) Paedomorphosis Descendant Ancestor BCD

4.12 Horn Length (mm) Basilar Length of Skull (mm)

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 Hormones Neurotransmitters Tamability Developmental program (simplified) Genes Correlated changes

4.14 Attack Frequency S1S1 S4S4 S Age (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 days of age Randomly assigned Enriched environment Impoverished environment Treatment duration (e.g., 30 days) Behavioral testing Chemical and morphological analyses of the CNS