Lecture 2 Porifera & Cnidaria

Phylum Porifera: The sponges

Evolutionary relationships  Why or Porifera considered animals rather than Protists?  How do they differ from other animals (3 ways…)?

Sponge structure  Review key parts…  No tissues, organs or body systems!

Water movement and feeding [choanocyte, Fig. 33.4]  Role of flagellum  Role of collar  Movement of particles  Phagocytosis

Amoebocytes  Move in amoeboid fashion through mesohyle  Secrete spicules and/or spongin  finish digestion  “Garbage-collector cells”  Transport waste to excurrent pore  Can develop into other cell types  Somewhat like stem cells!

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

Nudibranch (Phylum Mollusca, Class Gastropoda)

Phylum Cnidaria Hydrozoa Scyphozoa Cubozoa Anthozoa

Phylum Cnidaria

Evolutionary relationships

Radiata vs. Bilateria

Body organization

Key features  Polyps and medusae  Two germ tissue layers (called..?)  Mesoglia  Gastrovascular cavity (functions?)  Nervous system: nerve net  Neurons? Brain? Nerve cords (bundles of axons)?  Tentacles with cnidocytes (stinging cells)

Cnidocytes/nematocysts How do they work?

Life-history strategies