1. Chapter 28 Arthropods and Echinoderms

2. Introduction to Arthropods
“jointed feet”
Most diverse and successful animals
Over 750,000 species identified
Segmented bodies
Tough exoskeleton
Jointed appendages

3. Body Terms
Exoskeleton- external skeleton that protects and supports the body
Made of protein and a carbohydrate called chitin
Much variation on exoskeletons
Terrestrial arthropods (Ter. Arth.) have waxy covering to prevent water loss
Appendages- structures like legs and antennae that extend from the body wall

4. Evolution has led to: Fewer body segments
The body segments fused together
Highly specialized appendages
For feeding, movement, and more
Legs became: antennae, claws, wings, flippers, tails, mouthparts and walking legs

5. Form and Function Feeding
Varied eating habits- herbivores, carnivores, omnivores
Bloodsuckers, filter feeders, detritivores, parasites
Varied mouthparts- pincers, fangs, jaws

6. Respiration
Tracheal tubes- branching, air filled tubes that are in many ter. arth.
Spiracles- small openings alongside the body that allow air to enter and leave the tracheal tubes
Book lungs- organs with layers of respiratory tissue stacked ex) spiders
Gills- used by aquatic arthropods ex) crabs
Book gills- used by horseshoe crab

8. Circulation
Open circulatory system- well developed heart pumps blood  arteries  tissues sinus  collects around the heart and re-enters to be pumped through again

9. Excretion
Malpighian tubules- saclike organs that extract wastes from blood and add them to feces to move through the gut
Used in ter. Arth.
Diffusion- moves cellular waste from the body to the water
Used in aquatic arth.

10. Response All have a brain Well developed nervous system
Two nerves around the esophagus connect brain to the central nervous cord
Connects the ganglia which coordinate movement of legs and wings

11. Movement Well developed muscles controlled by nervous system
Individual muscles cells
Muscles generate force (to fly, walk, swim) by contracting a muscle and pulling on the exoskeleton

12. Reproduction and Molting
Terrestrial
Internal fertilization
Aquatic
Internal and external fertilization
Molting
When an arthropod sheds its entire exoskeleton and makes a larger one in its place
Controlled by the endocrine system with hormones

13. Subphyla of Arthropods
Crustacea – crabs, shrimp, crayfish
Chelicerata – spiders, ticks, scorpions
Uniramia – millipedes, centipedes
Class Insecta (no subphylum)– 3 part body, 3 pairs of legs

14. 28-4 Echinoderms “spiny skin”
Endoskeleton- hardened plates of calcium carbonate
Gives bumpy, irregular surface
Only live in the sea
No cephalization
Two sided- oral (with mouth)/aboral

15. Echinoderm Characteristics
Spiny skin
Internal skeleton
Water vascular system
Suction cup structure called tube feet
5 part radial symmetry
Larvae- bilaterally symmetrical
Deuterostomes

16. Water Vascular System
Carries out essential body functions like respiration, circulation and movement
Madreporite- opening to the outside through which water passes
Connects to ring canal which extend out into radial canals along the 5 arms
Tube feet- suction cups on the underside of the body that help with movement and feeding

18. Feeding Urchins- scrape algae Sea lilies- capture floating plankton
Sea cucumbers- take in sand and detritus off sea floor
Sea stars- use tube feet to pull open bivalves, push stomach out, pour enzymes and digest mollusks, brings back stomach into body

19. Respiration and Circulation
Water vascular system
Thin walled tissues of tube feet for respiration
Skin gills gas exchange

20. Excretion Digestive wastes- feces through anus
Ammonia excreted through tube feet

21. Response and Movement Don’t have highly developed nervous system
Nerve ring around the mouth
Sensory organs that detect light
Tube feet
Endoskeleton structure/flexible joints

22. Reproduction
External fertilization
Separate sexes

23. Groups of Echinoderms Urchins Sand dollars Brittle stars Sea cucumbers
Sea stars
Sea lilies
Feather stars

24. Ecology Urchins control algae Sea stars control clams and corals
Crown of Thorns
Feeds on corals
Rows of poisonous spines on arms
Great Barrier Reef damage