1. Trends in Animal Evolution Acoelomate Pseudocoelomate Body cavity endoderm mesoderm ectoderm Coelomate

2. Trends in Coelomate Evolution Cleavage Deuterostomes  Radial Cleavage Protostomes  Spiral Cleavage

3. Trends in Coelomate Evolution Coelom Formation Cells migrate from existing cell layers, forming a solid tissue layer which splits; mouth forms from opening Mesoderm forms from outpockets of endoderm; anus forms from opening Protostomes Deuterostomes Gastrula stage ectoderm endoderm coelom

4. The Coelomates Internal body cavities Skeletons (internal and external) 245 - 540 m.y.b.p. 66 - 245 m.y.b.p. 66 m.y.b.p. - present Coeloms & external skeletons

5. The Coelomates Advantages of External Shells/Skeletons Secretion of mineral shell (stores minerals) Protection from desiccation Protection from predators Muscle attachment (locomotion & strength)

6. Phylum Mollusca

7. Class Polyplacophora Class CaudofoveataClass Solenogastres Class Monoplacophora Class Scaphopoda Class Gastropoda Class Bivalvia Class Cephalopoda Subphylum Conchifera

8. protostomates mantle head foot Key Characteristics coelomates mosaic/determinant development

9. Cephalization head is well developed, with one or two pairs of antennae and, in some species, eyes Key Characteristics

10. radula

11. Key Characteristics Trocophore and Veliger Larvae

12. Class Caudofoveata Class Solenogastres (nee Class Aplacophora)

13. Class Polyplacophora The Chitons 8 shell plates mantle “girdle”

14. Class Monoplacophora

15. Class Scaphopoda

16. Class Gastropoda marine, freshwater, terrestrial well developed head with eyes and tentacles torsion

17. RESPIRATORY SYSTEM Gills Diffusion across skin “Lung”

18. TORSION BEFORE AFTER dorsal viewside view

19. FOULING PROBLEMS ASSOCIATED WITH TORSION

24. Class Bivalvia second largest class of molluscs mainly marine, with a few freshwater species no head, no radula, reduced cephalization

25. Locomotion hydraulics

26. Bivalve Gills used in feeding and oxygen uptake

28. Class Cephalopoda nautiloids squids octopus cuttlefish

29. Key Characteristics mantle surrounds viscera and forms siphon ink gland beak-like jaws large, circumoral tentacles/arms formed from foot image forming eyes & large brain shell present in all except octopods

30. Rotation of Body Axis

31. Nautiloid Shell shell is divided by a series of internal septa septa are perforated by body extension (the siphuncle) the siphuncle regulates buoyancy of the chambers septum siphuncle

32. Cephalopod Locomotion jet propulsion water is forced out of the mantle cavity through a siphon

33. Camouflage

34. http://hermes.mbl.edu/mrc/hanlon/video.html

35. mass of squid egg capsules close-up of egg capsules eggs in early stages of development

36. fertilized eggs late development- stage egg freshly hatched squidlet Direct development of the squid