{ Biology 112 Arthropods and Echinoderms

 Includes animals such as crabs, spiders, and insects  Segmented bodies, a tough exoskeleton (external body covering) and jointed appendages (legs and antennae that extend from the body wall)  Fewer body segments than worms and highly specialized appendages used for feeding, movement and other functions  Most only have 2-3 segments  Appendages include walking legs, antennae, wings and mouthparts Anthropods

 Herbivores, carnivores and omnivores  Most receive gases through a network of tracheal tubes that extend throughout body  Openings are called spiracles  Others have book lungs  Aquatic organisms have gills  Eliminate wastes through structures called Malpighian tubules  internal fertilization (terrestrial) and external for aquatic Functions of Arthropods

Body Structure

Arthropods and Exoskeleton  Arthropods outgrow their skeletons and molt  The entire skeleton is shed and manufactures a larger one to take its place

Groups of Arthropods  Classification is based on number of segments and appendages – particularly mouthparts  Crustaceans (Crustacea)  Chelicerates (Chelicerata)  Uniramians (Uniramia)

Crustaceans  Crabs, shrimp, lobster, crayfish, barnacles  Two pairs of antennae, 2-3 body segments (head, thorax and abdomen), chewing mouthparts called mandibles

Chelicerates  Horseshoe crabs, spiders, ticks, and scorpions  Have mouthparts called chelicerae and 2 body segments  Four pairs of walking legs  Spiders spin webs of silk

Uniramians  Centipedes, millipeds and insects  Have jaws, one pair of antennae, unbranched appendages  Most body segments have one pair of legs each

 Three body parts – head, thorax and abdomen  Three pairs of legs attached to the thorax  Usually, a pair of antennae, a pair of compound eyes, and two pairs of wings  Can detect changes in colour and movement  Three pairs of appendages used for mouthparts  Growth usually involves metamorphosis, the process of changing shape and form  Some are harmful to humans and others helpful  The communicate using sound, chemical and other types of signals  Some are also capable of forming societies Insects

 Sea stars, sea urchins, and sand dollars  Characterized by spiny skin, a water vascular system, and suction-like structures called tube feet  Have an endoskeleton, five part radial symmetry as adults and are all deuterosomes  Contain a water vascular system that is filled with fluid that carries out much of its life functions  A maldreporite Echinoderms