CHAPTER 13 p. 360 Mollusks, Echinoderms, and Arthropods Mollusks PHYLUM MOLLUSCA means “soft”. second largest phylum. Ex. Snails, clams, squids all have bilateral symmetry. SOME LIVE ON LAND MOST LIVE IN WATER MOLLUSK BODY PLAN FOUR BASIC PARTS 1) MANTLE - creates the shell. 2) VISCERAL MASS - internal organs. 3) SHELL - for protection. 4) FOOT (or headfoot) - for movement. - most have an open circulatory system. (the blood is not contained in vessels). CLASSIFYING MOLLUSKS 1)Bivalves - ex. clam, oyster, scallops. Class Bivalvia “ “ - also known as Class Pelycepoda “ “ -have a two-part shell linked by a hinge. - have a strong muscular foot for movement. Bivalves are filter feeders. MORE BIVALVES Scallops Oyster Scallop Giant Clam Bivalve Body Plan Gills Visceral mass Foot Mantle Shell 2) Univalves “ Ex. snails, conches, slugs. - in Class Gastropoda “ “ because they walk on their stomach. - have only one shell. “ Univalves are the largest class of mollusks. Triton Murex Slug Gastropods obtain food by scraping material off ‘rocks’. - they have a tongue-like organ called a radula. MORE GASTROPODS Land Snails Slug Edible Snail Conch SNAILS • Crawl on a layer of slime. • Land snails breathe with lungs. Water snails have gills • Snails cannot hear. • Snails are hermaphrodites. • Most travel about 23 inches per hour! 3) CLASS CEPHALOPODA • means “headfoot”. • includes octopus and squid. Squid Octopus Cephalopods are the most complex class. - have a closed circulatory system. - their ‘foot’ is their tentacles. MOVEMENT: JET PROPULSION CEPHALOPODS Chambered Nautilus - an “ancient” cephalopod. Octopus - eight tentacles. Squid - ten tentacles CEPHALOPOD FACTS • A cepholopod eye is somewhat similar to ours and is the animal kingdom’s largest. • The Giant Squid is over 65 feet in length. • Octopus swim ‘backwards’. • Squid and octopus do not have shells. • Some can release an “ink” to escape predators. • Most have a “beak” which can tear apart their prey. Importance of Mollusks 1) Food - clams, oysters, snails, calamari, octopus, etc. 2) Pearls • Created by the mantle. • It secretes nacre over an irritant (like a grain of sand). • Nacre is also called “mother of pearl”. • It takes many layers of nacre to make a pearl. REVIEW THE THREE MAJOR CLASSES < CLASS GASTROPODA CLASS BIVALVIA > < CLASS CEPHALOPODA ECHINODERMS (p. 380) Phylum Echinodermata ex. starfish, sea urchin - have radial symmetry. ‘ ‘ - some seastars have the ability to regenerate. - starfish have tubefeet on their tentacles which act like suction cups. - for movement and feeding. Starfish can ‘extend’ their stomachs to digest their prey. More echinoderms Crown of thorns seastar Sea Cucumber Pacific Seastar Sand Dollar ASSIGNMENT: WORKSHEET “MOLLUSCA” PHYLUM ARTHROPODA “ p. 370 - largest phylum of animals - more than all of the other phylums put together. - an estimated 10 million species. “ Arthropods are more complex. - they have respiratory circulatory nervous systems. - all have an open circulatory system. Respiratory System - water arthropods have “gills”. - land arthropods have air sacs/trachea. - air enters the book lungs thru holes called spiracles. Arthropods can have several pairs of appendages. Ex. legs, wings, pincers. Their bodies have a hard outer covering called an exoskeleton The exoskeleton does not grow. It must be molted or shed. - the new exoskelet on is soft and takes time to harden. ARTHROPOD CLASSES 1) Class insecta - largest class of arthropods. Ex. ants, grasshoppers, beetles, etc. Insects have three body regions. - all have six legs. - the only class able to fly. Insects have a compound eye (many lenses) and a pair of antennae (to sense) Insects are classified into orders according to its mouth parts (or how it eats). * chewing - grasshopper * piercing - mosquito * sucking - fly ASSIGNMENT: WORKSHEET “CLASS INSECTA” INSECT DEVELOPMENT Metamorphosis (p.372) - a change in form that an organism goes thru to become an adult. A) Complete metamorphosis Ex. butterfly 1) egg 2) larva (caterpillar) 3) pupa -inactive stage - forms a chrysalis (cocoon) 4) Adult Monarch larvae Chrysalis Complete Metamorphosis B) Incomplete metamorphosis Ex. grasshopper 1) egg 2) nymph - small adult - no wings - many molts to 3) Adult No real ‘change’ - it just grows larger. Which type of metamorphosis? Incomplete Complete 2) Class Arachnae “Arachnids” p. 374 Ex. spiders, ticks, scorpions. - have eight legs. - no antennae. Spiders have book lungs - air moves over structures that look like pages of an open book. - openings are called _____. Arachnids have two body parts. 1) cephalothorax - head and chest area. 2) abdomen - internal organs - arachnids have simple eyes - they can sense light/dark but cannot see images. Arachnids have more appendages than insects. stingers - at the end of the abdomen. Ex. scorpion fangs - inject poison - a paralyzer. - it also liquifies the prey’s inner parts. - the spider sucks it out. spinnerets - are tubes which ‘spit out’ material make webs and capture food. ASSIGNMENT: WORKSHEET “METAMORPHOSIS” 3) Class Myriapoda ‘myriapods’ “ p. 375 “ Centipede - “hundred legged” - many body segments. - eats other insects - has poison fangs. Millipede - “thousand legged” - many body segments. - eats dead plants. - one pair of legs per segment. - can move only one side at a time. - ‘wriggle’. - two pair of legs per segment. - can move both sides at a time. - smooth movement - stink glands if threatened. - slower. ASSIGNMENT: WORKSHEET ‘ARTHROPODS’ 4) Class Crustacea Ex. crab, lobster, shrimp - similar characteristics to arachnids. - two body parts “Crustaceans” p. 377 - but has many more appendages. - two pair of antennae to sense info about their environment. - claws - used to capture or hold prey. - also the first pair of legs. - four pairs of walking legs. - five pairs of swimmerets. - uropod - the fan shaped part of the tail. - used for swimming. - some can regenerate appendages. - have mandibles - jaws for chewing. - they also molt. - have compound eyes usually located on long stalks - more than one lense - can see movement better. - see over a wider area. -most live in water… not pill bugs - a huge source of food for people. More crustaceans… Crayfish Blue Crab Fiddler Crab Shrimp ASSIGNMENT: WORKSHEET “CRUSTACEANS” What are these structures? 3. 2. 1.