1. Invertebrates 1 Introduction, Porifera, Cnidaria

2. Lecture outline 1.Overview: Invertebrate lectures 2.What is an animal? 3.Introduction to major phyla in Kingdom Animalia 4.Basic phylogeny of Kingdom Animalia 5.Phylum Porifera 6.Phylum Cnidaria

3. 1. Overview of Invertebrate portion of course  Evolutionary relationships  Body plan  How animal meets its basic needs  Relationship of structure and function  Selected aspects of life-history and ecology

4. 2. What is an animal?  Eukaryotic  Multicellular: Multiple cell types (Not just many cells)  Heterotrophic  No cell wall  Characteristics of early development (unique!)  Blastula and gastrula stages unique to animals  Sponges, have precursors to these stages

5. Phylum Porifera: sponges

6. Phylum Cnidaria: Have Cnidocytes

7. Phylum Ctenophora: The comb jellies

8. Phylum Platyhelminthes: The flatworms

9. Phylum Nematoda: The roundworms

10. Phylum Annelida: The segmented worms

11. Phylum Mollusca: The “soft-bodied” animals

12. Phylum Arthropoda: Jointed appendages

13. Phylum Echinodermata: Spiny-skinned

14. Phylum Chordata: Animals with notochords

15. 4. Phylogenetic overview  Presumed to be monophyletic  Hypothesis assumes all animals evolve from a single common ancestor  That ancestor thought to be a sponge-like protist called a choanoflagellate  Modern choanoflagellate  Found in aquatic habitats  Some propose polyphyletic origins polyphyletic origins  Cite Cambrian explosion

17. Phylogenetic overview (“traditional”)

18. Multicellularity separates the ancestral protists from all animals  Multicellularity  Different types of cells!

19. Development of two true tissue layers  Separates Phylum Porifera from all others  Sponges All other groups (2-3 tissues)

20. Development of a third germ layer and bilateral symmetry  Cnidarians, Ctenophores All others  Radial symmetry, 2 layers Bilateral symmetry, 3 layers  (Porifera)

21. Further developments (briefly)

22. Body cavities  Acoelomate  Pseudocoelomates  Coelomates

23. Further developments (briefly)

24. 5. Phylum Porifera: The sponges

25. Evolutionary relationships  Simplest multicellular animals  Main cell type, choanocyte, resembles choanoflagellate cell  Considered "multicellular" rather than colonial, because there are different cell types.  Not much, if any cooperation between cells  No real "tissues", no "systems" of any type (no nervous system, circulatory system, etc.)

26. Sponge structure  Review key parts…

27. Water movement and feeding  Role of flagellum  Role of collar  Movement of particles  Phagocytosis

28. Protection  Sponges are sessile…  Toxins/warning coloration (this is why many sponges are brightly colored)  Painful or sharp covering (spicules)  Regenerative ability  Camouflage (if not toxic)  Bore into shells.  NOTE: Nudibranch predators co-opt sponge defenses (toxins, spicules)

29. Phylum Cnidaria

31. Evolutionary relationships  Diverge from the Porifera in the following ways:  Diploblastic: two true tissue layers  Ectoderm and endoderm  No mesoderm  Radiata: One of two phyla to exhibit radial symmetry

32. Where Cnidarians fit in…  Cnidarians, Ctenophores All others  Radial symmetry, 2 layers Bilateral symmetry, 3 layers  (Porifera)

33. Body organization  Polyps and medusae

34. Key features  Polyps and medusae  Tissue layers  Ectoderm, gastroderm (=endoderm)  Mesoglia  Secreted from the tissue layers  Gastrovascular cavity  Functions  Not a true body cavity!  Nervous system: nerve net  No other major body systems  Tentacles with cnidocytes (stinging cells)

35. Nervous system features   True neurons   Conduction can be unidirectional or bidirectional along neurons   Nerve net with no direct pathways   Have simple sensory organs

36. Cnidocytes/nematocysts How do they work?

37. Life-history strategies