Introduction to Introduction to Animal EvolutionAnimal Evolution

Def: an•i•mal (n)Def: an•i•mal (n)Unique characteristics:Unique characteristics:

Heterotrophic eukaryotes; ingestionHeterotrophic eukaryotes; ingestion

Lack cell walls; collagenLack cell walls; collagen

Nervous & muscular tissueNervous & muscular tissue

Sexual; diploid; cleavage; blastula; Sexual; diploid; cleavage; blastula; gastrulation; larvae; metamorphosisgastrulation; larvae; metamorphosis

Regulatory genes: Regulatory genes: HoxHox genes genes

Animal phylogeny & diversity, IAnimal phylogeny & diversity, IMonophyletic; colonial flagellated protist Monophyletic; colonial flagellated protist ancestorancestor

1- 1- Parazoa-Eumetazoa dichotomyParazoa-Eumetazoa dichotomy: : sponges (Parazoa)~ no true tissues; sponges (Parazoa)~ no true tissues; all other animals (Eumetazoa)~ true tissuesall other animals (Eumetazoa)~ true tissues

2- 2- Radiata-Bilateria dichotomyRadiata-Bilateria dichotomy: : Cnidaria (hydra; ‘jellyfish’; anemones) Cnidaria (hydra; ‘jellyfish’; anemones) ~ radial body symmetry; ~ radial body symmetry; all other animals ~ bilateral body symmetryall other animals ~ bilateral body symmetry (allows cephalization)(allows cephalization)

Animal phylogeny & diversity, IIAnimal phylogeny & diversity, II

3- 3- GastrulationGastrulation: germ layer development; : germ layer development; ectoderm ectoderm (outer), (outer), mesodermmesoderm (middle), (middle), endodermendoderm (inner); radiata (inner); radiata are are diploblasticdiploblastic-2 layers; no mesoderm; bilateria are -2 layers; no mesoderm; bilateria are triploblastictriploblastic-all 3 layer-all 3 layer

4- 4- Acoelomate, Pseudocoelomate, and Coelomate Acoelomate, Pseudocoelomate, and Coelomate GradesGrades: triploblastic animals~ solid body, no body : triploblastic animals~ solid body, no body cavity called cavity called acoelomatesacoelomates (Platyhelminthes-flatworms); (Platyhelminthes-flatworms); body cavity, but not lined with mesoderm called body cavity, but not lined with mesoderm called pseudocoelomatespseudocoelomates (Rotifers); true coelom (body cavity) (Rotifers); true coelom (body cavity) lined with mesoderm called lined with mesoderm called coelomatecoelomate

Side view of blastula and developing Side view of blastula and developing layers.layers.

Blue = ectoderm, Red = endoderm, White = mesoderm

Animal phylogeny & diversity, IIIAnimal phylogeny & diversity, III5- 5- Protostome-Deuterostome dichotomy among Protostome-Deuterostome dichotomy among coelomatescoelomates: protostomes (mollusks, annelids, : protostomes (mollusks, annelids, arthropods); deuterostomes (echinoderms, arthropods); deuterostomes (echinoderms, chordates) chordates)

a) cleavage: protostomes~ spiral and a) cleavage: protostomes~ spiral and determinate; deuterotomes~ radial and determinate; deuterotomes~ radial and indeterminate indeterminate

b) coelom formation: protostomes~ b) coelom formation: protostomes~ schizocoelous; deuterostomes~ enterocoelousschizocoelous; deuterostomes~ enterocoelous

c) blastopore fate: protostomes~ mouth from c) blastopore fate: protostomes~ mouth from blastopore; deuterostomes~ anus from blastoporeblastopore; deuterostomes~ anus from blastopore

AcoelomateAcoelomate-- no no cavitycavity

PseudocoelomPseudocoelom-- cavitity between cavitity between

endoderm and endoderm and mesodermmesoderm

CoelomateCoelomate- cavity - cavity located within the located within the

mesoderm.mesoderm.

Coelomate developmentCoelomate development