Chapter 33Wednesday, April 6, 20161:42 PM Chapter 33 - Introduction to Invertebrates Introduction to Invertebrateso~95% of all animal specieso~35 phylaoMost are aquatic (freshwater or marine)-Big exception: arthropods have many land species-Animal form follows functionoFocus on adaptations for lifestyle and habitat;-Sensing-Locomotion-Food type, ingestion, and digestion-Internal transport (circulation)-O2/ CO2 exchange (respiration)-Getting rid of metabolic waste (excretion)-Water balance (osmoregulation)-Defense mechanisms-Reproduction*Be able to list what each animal does* Basal Animals: Porifera (Sponges)-Phylum Porifera: the SpongesoBasal animals - basal metazoansoAquatic, mostly marineoLack overall symmetry-Sessile as adults - grows attached to an organismoSponges are filter feeders-= feed by passing water across structures that trap tiny food bits Water flows through pore cells into inter chamber called spongocoelVideo: fluorescent dye passing through pores quickly-Choanocytes create currents; trap and ingest food bits (phagocytosis)Food bits get moved to main body and ingested by phagocytosis - intracellular digestion-Amoebocytes distribute foodTransferred to amoebocytesJellylike part, amoeboid movement to distribute food to other cells in the sponge-All digestion intracellularoLack true tissues-Feeding, digestion, gas exchange, waste removal all at cellular level[33.4] Learn the parts and their functions-Cell types often change rolesSpicules (secreted by amoebocytes)Choanocytes <> amoebocytes <> pore cellsoBody supported by hard spicules and protein fibers (spongin)-Made by amoebocytes in mesohyloReproduction-By fragmentation-Sexually; hermaphroditic (M or F at different times)No gonads: gametes form in mesohylFlagellated larvae disperse, then settle Basal Eumetazoans: Cnidaria-Phylum Cnidaria (refers to the way they get food)oRadial symmetryoAquatic, in two adult body forms-Sessile polyp-Drifting/free-swimming medusaoAquatic "sit and wait" carnivores:-Stinging tentacles around central mouth catch prey and cnidocytes-Video: don't reach for prey - have to make direct contact with tentacles before they can catch preyoSac-like body with gastrovascular cavity-Gastro1 opening (mouth/anus) to digestive sacExtracellular and intracellular digestion-Vascularg-v cavity distributes nutrients to entire bodyoDiploblastic with gel (mesoglea) in between layers-Direct O2/CO2 exchanging between cells and water-Metabolic waste easily diffuses outMoving with nerve cells and have muscle fibers in epidermal cells-Epidermis and gastrodermis have contractile cells, coordinated by a simple nervenetMedusa-e "swim" by contractions of their bell formoReproduction sexual and/or by budding-Many cycle through polyp form and medusa formEx. ObeliaAll diploid-Zygote through cleavage-Flagellated larvae - to get to new location-Initiate transformation of form into polyp-Gastrointestinal cavity-Medusa develops the gonads-Cnidarian DiversityoFreshwater Cnidarian - Hydrao"Portuguese man-of-war" is a colony of polyps (marine)oJellies "jellyfish" are marine and free-swimming-Bioluminescent-Ex. Corals, sea anemones, box jellies Basal Eumetazoans: Ctenophora-Phylum Ctenophorao"Comb jellies" are radially symmetric and diploblastic-Transparent, medusa-like body-Moves with cilia, fused into 8 comb-like platesoMarine "sit and wait" carnivores-Only two tentacles (or none)Cells eject a sticky thread to capture prey Lophotrochozoans: Platyhelminthes-Phylum Platyhelminthes: flatwormsoFlat, triploblastic, acoelomate with bilateral symmetry-Mesoderm-derived muscle tissuesoThin body means high SA/V ratio-O2/CO2 exchange is at cell level-Metabolic wastes removed at cell leveloMany organs:-Gastrovascular cavity with 1 openingHighly branched to distribute nutrients-Muscular pharynx - suck in food for digestion-Shows something about a nervous system, with real nerve cords-Simple nervous system:Eyespots - detect light, avoid the lightGanglia (simple brain)Ventral nerve cords-Protonephridia with flame bulbs remove excess water and some wastesoFlatworm diversity-PlanariansFree-living carnivores or scavengers-Trematodes (flukes)Parasitic on animals and with complex life cycles-To complete life cycle, they have to go through two or more hostsEx. Schistosoma (blood flukes) cause schistosomiasis-TapewormsParasitic mostly in vertebrate intestinesNo mouth or digestive system (absorptive)Anterior scolex for attachmentRepeated reproductive segments (proglottids) fill up with eggsLophotrochozoans: Rotifera-Phylum Rotifera: rotifers-"rotating" "bearing"-Free-living, aquatic-Microscopic, cylindrical body-Rotating wheel of cilia brings plankton to mouth-Uses cilia to generate a current, pulls planktonic foods-Well-developed organ systems:-Alimentary canal (mouth-tube-anus):Flow-thru food processingSpecialized digestive regions-Pseudocoelom acts as circulatory system-Food digested here…delivers nutrients to the body-No blood vessels at all-Many species only reproduce by parthenogenesis Lophotrochozoans: Ectoprocta and Brachiopoda-Two "Lophophorate" PhylaoCommon features-Aquatic, sessile suspension-feeders, using a lophophoreHorseshoe ring of mucus-coated, ciliated tentacles trap and move food bits to mouth-U-shaped alimentary tract-No head-True coelom-Phylum Ectoproctao"outside" "anus"oMouth at base of lophophore to bring mucus ino"Bryozoans" or "moss animals"-Colonial; mostly marine-Most with mineralized exoskeletonoPhylum Brachiopodao"brachiopods" or "lampshells"-Lophophore as feeding apparatus-Marine, with two shells (analogous to bivalve mollusks) and pedicle (for attachment, suspension)-Very diverse in fossil record; few species today Lophotrochozoans: Mollusca-Phylum MolluscaoCommon body plan:-Muscular foot: locomotion, digging (used for burrowing, functional equivalent tolegs)-Visceral mass: internal organsWell-developed organ systems (kidney - rid of metabolic wastes, gets fluids past through kidney)Open circulatory system (most have a heart and vessels)-Mantle: covers visceral mass; makes shell (if present) and pearlTissue layer, job is to protect visceral massForms mantle cavity with gills or lungs (O2/CO2 exchange)oOther mollusk features:-Shell present in most mollusksSecreted by mantle tissueCaCO3 in a protein matrix-Many feed with radulaScrapping up food (teeth made of chitin)Modified in some-Most with