Chapter 28: Arthropods and Echinoderms

What is an Arthropod? Segmented body Segmented body Tough exoskeleton of chitin Tough exoskeleton of chitin Jointed appendages Jointed appendages Largest animal phylum Largest animal phylum Insects, crabs, spiders, and centipedes Insects, crabs, spiders, and centipedes

Other characteristics of arthropods: Evolution: fewer segments and more specialized appendages Evolution: fewer segments and more specialized appendages Feeding: herbivores, carnivores or omnivores with specialized mouthparts Feeding: herbivores, carnivores or omnivores with specialized mouthparts Respiration: air enters through spiracles and branch out through tracheal tubes. Spiders use book lungs and aquatic species use gills Respiration: air enters through spiracles and branch out through tracheal tubes. Spiders use book lungs and aquatic species use gills book lungs book lungs Circulation: most have a heart and an open circulatory system Circulation: most have a heart and an open circulatory system

More characteristics of arthropods: Excretion: terrestrial species have Malpighian tubules while some aquatic species excrete wastes by diffusion. Crayfish have green glands. Excretion: terrestrial species have Malpighian tubules while some aquatic species excrete wastes by diffusion. Crayfish have green glands. Response: all have brains and ventral nerve cords with ganglia Response: all have brains and ventral nerve cords with ganglia Movement: muscle cells that can contract and expand Movement: muscle cells that can contract and expand Reproduction: separate sexes with internal fertilization with terrestrial species. Reproduction: separate sexes with internal fertilization with terrestrial species.

How do arthropods grow? Molting: hormones trigger the process in which arthropods shed their old exoskeleton and secrete a larger one. Molting: hormones trigger the process in which arthropods shed their old exoskeleton and secrete a larger one. Molting The new exoskeleton is soft at the start leaving the animal vulnerable until it hardens, The new exoskeleton is soft at the start leaving the animal vulnerable until it hardens,

What are the different subphyla of arthropods? Crustaceans: crabs, shrimp, lobster, barnacles Crustaceans: crabs, shrimp, lobster, barnacles Chelicerates: spiders, ticks, horseshoe crab, and scorpions Chelicerates: spiders, ticks, horseshoe crab, and scorpions Chelicerateshorseshoe crab Chelicerateshorseshoe crab Uniramia: insects (largest class of animals), centipedes, and millipedes Uniramia: insects (largest class of animals), centipedes, and millipedesmillipedes

What are insects? 3 body parts: head, thorax, abdomen 3 body parts: head, thorax, abdomen 3 body parts 3 body parts 3 pairs of legs attached to thorax 3 pairs of legs attached to thorax Antennae and compound eyes Antennae and compound eyes

Special adaptations of insects: Response: compound eyes, chemical receptors and pheromones, developed ears Response: compound eyes, chemical receptors and pheromones, developed ears Feeding: 3 pairs of mouthparts (mandibles) Feeding: 3 pairs of mouthparts (mandibles) Feeding Metamorphosis: some insects change shape and form as they grow Metamorphosis: some insects change shape and form as they grow Metamorphosis Complete: egg, larva, pupa, adult Complete: egg, larva, pupa, adult Incomplete: egg, nymph, adult Incomplete: egg, nymph, adult Insect societies Insect societies Insect societies Insect societies

What is an echinoderm? Spiny skin Spiny skin Endoskeleton Endoskeleton Water-vascular system with tube feet Water-vascular system with tube feet Most adults have 5 part radial symmetry Most adults have 5 part radial symmetry Include sea stars, sea cucumbers, sea urchins and brittle stars Include sea stars, sea cucumbers, sea urchins and brittle stars

Echinoderm form and function Water vascular system: madreporite is connected to the ring canal which is then connected to the radial canals through which water travels for movement (along with tube feet), circulation and respiration Water vascular system: madreporite is connected to the ring canal which is then connected to the radial canals through which water travels for movement (along with tube feet), circulation and respiration Water vascular system Water vascular system Response: eyespot, nerve ring and radial nerves Response: eyespot, nerve ring and radial nerves Feeding: pushes stomach out over prey and digests the prey, wastes exit the anus Feeding: pushes stomach out over prey and digests the prey, wastes exit the anus Reproduction: separate sexes with external fertilization Reproduction: separate sexes with external fertilization