Invertebrates vs. Vertebrates Chapters 33 &34
Invertebrate Diversity Invertebrates are animals that lack a backbone Evolved first Earliest invertebrates were sponges (lack tissue and organs, suspensions feeders through pores, lack symmetry) Sponges have “choanocytes” (a.k.a. collar cells) or flagellated cells that ingest food
Cnidarians (Jelly Fish) Radial Symmetry Marine carnivores Stinging structures known as Cnidae Gastrovascular cavity (single opening digestion)
Bilateral Symmetry Central longitudinal plane that divides the body into two equal but opposite halves Flatworms were the first to develop bilateral symmetry Do not have gastrovascular cavity (no digestive tract) No segmentation
Molluscs Muscular foot Visceral Mass (contains internal organs) Mantle (fold of tissue that secretes a shell) Most molluscs have separate sexes
Annelids (segmented worms) Coelomates with segmented body wall and internal organs digestive tract is not segmented
Nematodes
nonsegmented covered by a tough cuticle
Arthropods Specialized segments and appendages Exoskeleton made of chitin Exoskeleton undergoes regular molting (ecdysis)
Echinoderms Tube feet used for locomotion and feeding radial anatomy evolved from bilateral symmetry skin covers endoskeleton
Vertebrates Bilateral symmetry Notochord (long, flexible rod located between digestive tract and nerve cord) has fluid-filled cells that if kept, turn into discs of spinal column Dorsal, hollow nerve cord Muscular, post-anal tail
