Mollusks, Arthropods & Echinoderms

Life Science - Middle School

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Arthropods Arthropods are the most advanced invertebrates. They have external skeletons, segmented bodies, and jointed attachments called appendages. Most arthropods have bilateral symmetry, an open circulatory system, a digestive system with two openings, and reproduce sexually. Spiders, grasshoppers, crabs, lobsters, centipedes and scorpions are examples of arthropods. Mollusk Mollusks are invertebrate animals with soft bodies. They are usually protected by an outer hard shell. Mollusks have a mantle, a thin layer of tissue covering their internal organs. They move using a thick muscular organ called a foot. Snails, octopuses, clams, and oysters are examples of mollusks. Body Structure Mollusks have bilateral symmetry and internal organs that are located in one area. Some of the internal organs include a stomach, heart, reproductive organs, and a pair of kidneys. Most mollusks have an open circulatory system. Mollusks that live in water use gills to obtain oxygen from the water. Echinoderms Echinoderms are invertebrates with an internal skeleton, called the endoskeleton. All echinoderms live in the ocean and most have spiny skins. The water-vascular system of fluid-filled tubes helps echinoderms move and catch food. Adult echinoderms have radial symmetry in which the body parts, usually in multiples of five, are arranged like spokes on a wheel. Examples of echinoderms include sea stars, sea urchins, sand dollars, and sea cucumbers. legs mantle mantle mantle anus anus anus crop gill gill gut gill coelom eye eye mouth mouth mouth adductor muscle siphon ink sac foot foot siphon nerve cord stomach stomach heart heart clam snail Sea star Sea urchin Sea cucumber Comparison of Arthropod Groups Crustaceans 2 or 3 2 2 3 5 or more 4 many 3 2 none 1 1 Characteristic Number of body sections Pairs of legs Pairs of antennae Arachnids Insects © Copyright NewPath Learning. All Rights Reserved. 94-4708 www.newpathlearning.com Mollusks, Arthropods & Echinoderms squid stomach ring canal tube feet
Arthropods Arthropods are the most advanced ________________. They have ________________ skeletons, ________________ bodies, and jointed attachments called ________________. Most arthropods have ________________ symmetry an ________________ circulatory system, a digestive system with ______________ openings and reproduce ________________. Examples of arthropods include __________ _____________________________________. Mollusk Mollusks are ________________ animals with ________________ bodies. They are usually protected by an outer ________________. Mollusks have a ________________, a thin layer of tissue covering their internal organs. They move using a thick muscular organ called a ________________. Examples of mollusks include ______________________________________________. Body Structure Mollusks have _________________ symmetry and internal organs that are located in one area. Some of the internal organs include a stomach, heart, reproductive organs, and a pair of kidneys. Most mollusks have an ______________ circulatory system. Mollusks that live in water use ______________ to obtain oxygen from the water. Echinoderms Echinoderms are ________________ with an internal skeleton, called the ________________. All echinoderms live in the ________________ and most have ________________ skins. ______________________________ of fluid-filled tubes helps echinoderms move and catch food. Adult echinoderms have ________________ symmetry in which the body parts, usually in multiples of five, are arranged like spokes on a wheel. Examples of echinoderms include ____________________________________ ____________________________________. legs mantle mantle anus anus anus crop gill gut coelom eye eye mouth mouth adductor muscle siphon ink sac foot nerve cord stomach stomach heart clam snail Comparison of Arthropod Groups Crustaceans Characteristic Number of body sections Pairs of legs Pairs of antennae Arachnids Insects © Copyright NewPath Learning. All Rights Reserved. 94-4708 www.newpathlearning.com Mollusks, Arthropods & Echinoderms squid Key Vocabulary Terms appendages mantle arthropods mollusks bilateral symmetry open circulatory system echinoderm radial symmetry endoskeleton sea star external skeleton sea urchin gills segmented body invertebrate water-vascular system \|xiBAHBDy01761lz[