BIOL Invertebrates FINAL

Porifera (Sponges):

  • 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)

Annelida:

  • Segmented, true coelom

  • Closed circulatory system

  • Includes earthworms, polychaetes, leeches

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)