1. Unit 8 Invertebrates Ch. 28 Arthropods & Echinoderms

2. What Is an Arthropod?  Arthropods have a segmented body, a tough exoskeleton, & jointed appendages  Includes: insects, crabs, centipedes, & spiders

3. What Is an Arthropod?  Exoskeleton - tough external covering, made of chitin, it protects & supports  Chitin - a carbohydrate  Appendages - structures such as legs & antennae that extend from the body wall

4. Evolution of Arthropods  The evolution of arthropods, by natural selection & other processes, has led to fewer body segments & highly specialized appendages for feeding, movement, & other functions

5. Growth & Development in Arthropods  When they outgrow their exoskeletons, arthropods undergo periods of molting  Molting - when an organism sheds its entire exoskeleton & makes a larger one to take its place  It is controlled by the arthropod’s endocrine system, which regulates body processes by hormones

6. Groups of Arthropods  Arthropods are classified based on the # & structure of their body segments & appendages - particularly their mouth parts  The 3 major groups of arthropods are crustaceans, spiders & their relatives, & insects & their relatives

7. Groups of Arthropods  Crustaceans typically have 2 pairs of antennae, 2 or 3 body sections, & chewing mouthparts called mandibles

8. Groups of Arthropods  Spiders & their relatives have mouthparts called chelicerae & 2 body sections, & nearly all have 4 pairs of walking legs

9. Groups of Arthropods  Insects & their relatives have jaws, 1 pair of antennae, & unbranched appendages  Includes: centipedes & millipedes

10. What Is an Insect?  Insects have a body divided into 3 parts - head, thorax, & abdomen  3 pairs of legs are attached to the thorax

11. Insect Communication  Insects communicate using sound, visual, chemical, & other types of signals

12. Insect Societies  Ants, bees, termites, & some of their relatives form complex associations called societies  Society - a group of closely related animals of the same species that work together for the benefit of the whole group

13. What Is an Echinoderm?  Echinoderms are characterized by spiny skin, an internal skeleton, a water vascular system, & suction-cuplike structures called tube feet  Most adult echinoderms exhibit 5-part radial symmetry

14. Form & Function in Echinoderms  The water vascular system, which is filled with fluid, carries out many essential body functions in echinoderms, including: respiration, circulation, & movement

15. Groups of Echinoderms  Classes of echinoderms include sea urchins & sand dollars; brittle stars; sea cucumbers; sea stars; sea lilies & feather stars