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Kingdom: Animalia Phylum Mollusca Body Plan: Two Main Regions *Head *Foot mouth Large muscle used sensory organs for locomotion *Visceral mass contains heart, organs of digestion, excretion, and reproduction *Mantle - layer of epidermis covering the visceral mass Phylum: Mollusca Class: Gastropoda • • • • Stomach Foot Conch, snails, abalones (single shell) Slugs and nudibranchs (no shell) Open Circulatory System – no blood vessels – Organs are bathed in blood Torsion: during larval development the visceral mass twists around 180 degrees *allows animal to withdraw inside shell as an adult • mantle secretes calcium carbonate shell • Protects gills • Ganglia - paired clusters of nerve cells • Radula - flexible, tongue-like strip of tissue covered with tough, abrasive teeth • • • • • • Phylum: Mollusca Class: Pelecypoda Hatchet Foot Clams, oysters, and scallops Bivalves (two shells) Adductor muscles that open and close the shell Open Circulatory Filter feeders Shell (consists of three layers) 1. Outer layer protects against acidity of water 2. Middle layer of calcium carbonate strengthens the shell 3. Inner prismatic layer protects the animals soft body *Pearl - grain of sand between the mantle it gets coated with the inner layer • Cilia on gills create water current – incurrent siphon – excurrent siphon • • • • • • • • • Hinge Umbo Muscle Scars Mantle Scar Foot Visceral Mass - organs Gills Digestive Gland - green Pedipalps-reproductive organ Clam Phylum: Mollusca Class: Cephalopoda •Head Foot •Octopuses, squids, cuttlefish, and chambered nautilus • Free swimming, predatory existence • Circle of tentacles with powerful suction cups • Beak • Brain-largest of all invertebrates • Closed Circulatory System • Chromatophores-pigment cells Class: Cephalopoda (Squid) • Ten tentacles - longest two used for capturing prey • Muscular mantle propels squid with jet propulsion • The giant squid: Architeuthis may reach 43 feet Worlds 2nd largest invertebrate • Ink Sac • Siphon • Male/Female • Pen (internal skeleton-remnant of shell) • Beak Class: Cephalopoda Octopus and Chambered Nautilus • Octopus eight tentacles jet propulsion more likely to crawl along bottom no shell • Chambered Nautilus only cephalopod with external shell shell with gas-filled chambers for buoyancy Kingdom: Animalia Phylum: Annelida Earthworms, leeches, etc. Characteristics and Classification • Bilaterally symmetrical • Segmented worms – allows for efficient movement (shortening & lengthening of the body) • Setae – external bristles • Parapodia – fleshy protrusions • # of setae and presence or absence of parapodia divide the phylum into 3 classes Class Oligochaeta “few bristles” • • • • Live in soil or in fresh water No parapodia Few setae on each segment Ex: earthworm Earthworm: Lumbricus terrestris • Nocturnal Structure and Movement • More than 100 segments • Circular and longitudinal muscles • Setae grip the ground Feeding & Digestion • Pharynx esophagus crop gizzard long intestine anus • Crop – temporarily stores food • Gizzard – grinds soil up to remove nutrients • Maintain fertility of soil • Aerate soil and loosen soil • Closed circulatory system • Ventral & Dorsal blood vessel • Aortic arches – five pairs of muscular tubes Respiration • Oxygen and carbon dioxide diffuse directly through the skin (moist) Excretion • Nephridia – excretory tubules in each segment except first 3 and the last one • Chain of ganglia connected by a ventral nerve cord • Several ganglia are fused in the anterior segments to form the cerebral ganglia (brain) • process simple senses – light, touch, chemicals, moisture, T, and vibrations Reproduction • Hermaphrodites (can’t fertilize own eggs) • Clitellum – thickened region secretes mucus • Sperm is secreted into the mucus and travels to the Seminal receptacles (stored) Class Polychaeta “many bristles” • • • • • • Numerous setae & parapodia Parapodia function in gas exchange Antennae and specialized mouthparts Most live in marine habitats Some are free-swimming predators Others feed on sediment as they burrow for food Class: Hirudinea (leeches) • Live in calm bodies of fresh water or moist vegetation • No setae; no parapodia • Sucker at each end of their bodies used to attach to surfaces • Some are parasitic – can secrete an anesthetic and an anticoagulant so they can feed on blood • Can ingest 10X their own body weight