BIOL Invertebrates FINAL

Porifera

• No true tissues, asymmetrical

• Choanocytes (collar cells) for filter feeding

• Skeletal support: spicules and/or spongin

• Asexual (budding) and sexual (hermaphroditic)

• Sessile adults, motile larvae

Ctenophora (Comb jellies)

• Diploblastic, radial symmetry

• Move via 8 rows of cilia (combs)

• No cnidocytes; instead use sticky colloblasts

• Complete gut (mouth + anal pores)

• Often bioluminescent

Acoela:

• Previously grouped with flatworms, now its own phylum

• Acoelomate, triploblastic, bilateral symmetry

• Very simple nervous system

• No body cavity, no circulatory or respiratory system

• Live between sand grains or as marine flatworms

Platyhelminthes (Flatworms):

• Acoelomate, triploblastic

• Gastrovascular cavity with one opening

• Free-living (e.g., planarians) or parasitic (e.g., flukes, tapeworms)

• Show cephalization; simple nerve cords

Syndermata (includes Rotifers & Acanthocephalans):

• Pseudocoelomate, complete gut

• Rotifers have corona (cilia for feeding), jaws (trophi)

• Acanthocephalans are parasites of vertebrates

Ectoprocta & Brachiopoda (Lophophorates):

• Possess a lophophore: crown of ciliated tentacles

• Coelomates, filter feeders

• Sessile, often colonial (ectoprocts)

• Brachiopods have dorsal/ventral shell (unlike bivalves)

Mollusca:

• Body plan: muscular foot, visceral mass, mantle

• Most with radula (not in bivalves)

• Classes:

  • Gastropods (snails/slugs),

  • Bivalves (clams, oysters),

  • Cephalopods (squids, octopuses – closed circulatory system)

Nematoda (Roundworms):

• Pseudocoelom, unsegmented

• Covered by cuticle (molts)

• No circulatory system; complete gut

• Some parasitic: Trichinella, Wuchereria

Tardigrada (Water bears):

• Tiny, segmented

• Can survive extreme conditions

• Feed by piercing plant/animal cells

Arthropoda

• Segmented body, jointed appendages, chitin exoskeleton

• Must molt to grow

• Major subgroups:

  • Chelicerates (spiders, scorpions),

  • Myriapods (millipedes, centipedes),

  • Crustaceans (crabs, shrimp),

  • Hexapods (insects – tracheal gas exchange)

Hemichordata:

• Acorn worms

• Pharyngeal slits and dorsal nerve cord

• Marine, burrowing

• Sister group to echinoderms and chordates

Echinodermata:

• Pentaradial symmetry (adults), bilateral larvae

• Water vascular system with tube feet

• Endoskeleton of calcium carbonate

• Includes: sea stars, urchins, sea cucumbers

Chordata:

• 4 key traits (at some point in life):

  • Notochord

  • Dorsal hollow nerve cord

  • Pharyngeal slits

  • Post-anal tail

• Includes vertebrates and two invertebrate subphyla:

  • Cephalochordata (lancelets)

  • Urochordata (tunicates)