Chapter 33 Invertebrates About 95 of all animal species are invertebrates Composed of about 35 phyla Most are aquatic marine the big exception to this are the arthropods Porifera Closest group to the earliest animals Aquatic mostly marine Lake overall symmetry o Sessile as adults Lack true tissues 33 4 o Digestion gas exchange waste removal all occur at the cellular level o Cell types often change roles Body supported by hard spicules and or protein fibers called spongin Suspension feeders o Feed by passing water across a stick structure that catches tiny food bits o Choanocytes create currents that trap food Reproduction o By fragmentation o Sexually hermaphroditic o Flagellated larva disperses then settles Cnidaria Radial symmetry and diploblastic oral and aboral sides in attaches species 2 body forms in the life cycle o Sessile polyp o Planktonic free swimming medusa Body is sac like o 2 tissue layers with gel mesoglea in between Direct gas exchange between cells and water o Have a gastro vascular cavity 1 opening digestive sac mouth and anus as one hole Extracellular and intracellular digestion Gastro vascular cavity distributes nutrients to the entire body Aquatic sit and wait carnivores o Catch prey with stinging tentacles with cnidocytes Reproduction is sexual or asexual budding o Many cycle through polyp and medusa forms Hydrozoans o Ex Hydra is freshwater o All other classes are strictly marine o Most alternate between polyp and medusa 33 8 o Many are colonial polyps Obelia o Unusual body forms Portuguese Man of War Scyphozoans o Jellies medusa form predominately o Bioluminescent florescent o Nematocyst Cubazoans o Box shaped medusa with eyes o Very toxic sting ex Sea Wasp o Eyes why No brain to process images but can sense Anthozoans o Polyp form only o Anemones are solitary o Corals mostly colonial reef builders Ctenophores Comb jellies radial symmetry and diploblastic o Transparent medusa like body o Moves by 8 comb like plates of fused cilia Marine sit and wait carnivores o Usually two tentacles Cells eject a sticky thread to capture prey Lophotrochozoans Platyhelminthes Flat triploblastic solid body with bilateral symmetry Acoelomate Many organs o Gastro vascular cavity with 1 opening Highly branched to distribute nutrients o Nerve cords and ganglia and eyespots Gas exchange at the cellular level Turbellaria o 33 9 10 o Free living carnivores scavengers o Ex Planarian Trematoda o All are flukes parasites in animals o Ex liver flukes o Ex schist soma blood flukes cause schostosomiasis dysentery anemia complex life cycle Cestoidea o Parasitic tapeworm 33 12 Mostly in vertebrate intestines o No mouth or digestive system absorptive o Scolex attaches to intestinal wall o Repeated reproductive segments proglottids filled with eggs Rotifera Free living fresh water marine microscopic Rotating wheel of cilia feeding on plankton Well developed organ systems o Alimentary canal mouth tube anus o Cerebral ganglia o Muscles Pseudo coelom acts as a circulatory system Many species reproduce by parthenogenesis o Development of a female from an egg without fertilization Ectoprocta and Brachiopoda 2 lophophorate phyla common features o Aquatic sessile suspension feeders using a lophophore o U shaped alimentary canal o No head o Coelomate true coelom Ectoprocta o Bryozoans or moss animals marine Colonial making exoskeleton Brachiopods o Brachiopods or Lampshells Resemble bivalve mollusks Much more diverse in the fossil record than today o Pedicle attaches to some surface o Anterior posterior left and right Mollusca Common body plan 33 15 o Muscular foot used for locomotion or digging o Visceral mass internal organs Well developed organ systems Most have an open circulatory system o Mantle Covers visceral mass makes shell and pearls Forms mantle cavity with gills or lungs for gas exchange o May feed with a radula Scrapes up food o Most with separate sexes except snails Most aquatic species have trochophore larva Polyplacophora Chitons o 8 dorsal plates from shell o No distinct heat but do have anterior and posterior o Marine intertidal grazers o Basic and primitive mollusk Gastropoda o Largest class land fresh water marine o Single shell or no shell use a radula to feed o Torsion moves the mantle cavity over the head 33 18 Gives the animal a space to retract into the shell o Some eat plants and algae o Some are predators o Some are land adapted snails and slugs o Many are freshwater Schistosomiasis host snail o Marine environment Include shell less sea slugs and nudibranchs Bivalvia o Two part shell jointed by a hinge o No distinct head o Freshwater or marine suspension feeders burrowing sessile o Filter with gills no radula 33 20 Cephalopoda o Active marine predators 33 21 Foot modified into grasping arms and tentacles Beak like jaws often with poison Well developed eyes and brain especially in the octopus o Water jet propulsion excurrent siphon and mantle cavity o Protective ink and color changes o Ammonites dominant and diverse shelled cephalopods during the Mesozoic o Nautilus only living cephalopod with and external shell Closest to ammonites Uses shell to help float and move up or down in the water column o Squids and cuttlefish have a reduced internal shell o Octopi have no shell Annelida Segmented worms Common features 33 24 o Segmentation external and internal features are repeated Reduced in leeches o Closed circulatory system Blood and tissue separate Gas and nutrient exchange across capillary beds o Other well developed organ systems Digestive Excretory Nervous o True coelom acts as a hydrostatic skeleton 50 35 Polycheata o Fleshy appendages parapodia and many bristles 33 23 o All are marine o Bristle worms are active predators with jaws o Fan worms are sessile suspension feeders Oligochaeta o With few bristles and no parapodia o Reduced head o Terrestrial or freshwater o Earth worms eat dirt and aerate the soil o Leeches freshwater blood sucking parasites Suckers at both ends Anti coagulant in saliva Some on land Ecdysozoans Nematoda Colorless round body with tapered ends Thick flexible cuticle outer coat that is shed as it grows ecdysis primarily made of collagen C elegan used as an important research animal due to its simplicity can track every cell Dell developed digestive tract nerve cords gonads No circulatory system o Pseudo coelom distributes nutrients absorbed by the gut Pseudocoelm acts as a hydrostatic skeleton o Only have longitudinal muscles o Distinctive