1. Introduction to Animal Evolution
AP Biology
Crosby High School

2. Characteristics of an Animal
Multicellular, heterotrophic eukaryotes
No cell wall
Nervous tissue and muscle tissue
Life History (Sexual rep. dominated by 2n)
Fertilization creates 2n zygote
Cleavage divides into multiple cells (blastula)
Gastrulation: produces germ layers (gastrula)
Many have larval stages

3. Traditional Phylogenetic Tree
Parazoa – Eumetozoa Dichotomy
Phylum Porifera (sponges) lack true tissue
Radiata – Bilateria Dichotomy
Radiata (radial symmetry w/ oral & aboral)
Bilateria (Dorsal & ventral; Anterior & Posterior)
Usually associated w/ cephalization
Gastrulation creates concentric germ layers

4. Traditional Phylogenetic Tree (cont.)
Body Cavities
Acoelomate: no body cavity
Pseudocoelomate: cavity not completely derived from mesoderm
Coelomate: completely derived cavity
Cushions
Independent movement of organs

5. Phylogenetic Tree (cont.)
Protostome – Deuterostome Dichotomy
Cleavage
Protostome: spiral cleavage
Deuterostome: radial cleavage
Coelom
Schizocoelous
Enterocoelous
Blastopore Fate
Protostome: “Protos” (first), “Stoma” (mouth)
Deuterostome: “Deutero” (second)

6. Molecular Systematic Tree
Similarities
Parazoa – Eumetazoa
Radiata – Bilateria
Deuterostomes
Differences
Two Protostome Clades
Lophotrochozoa
Ecdysozoa
Annelid & Mollusk relationship based on trochophore larva

7. Differences Relocation of Acoelomates and Pseudocoelomates
Phylum Platyhelminthes no longer primitive “pre-coelomate”
Ecdysozoans named for ecdysis
Lophophorate Phyla
Placed under Lophotrochozoa

8. Molecular Systematics Tree

9. Proto vs. Deutero

10. Body Cavities

11. Radial vs. Bilateral

12. Phylogenetic Tree