Unit #5 Exam Review

1. Unit #5 Exam Review Echinoderms, Crustaceans, and Mollusks

2. Sea star, brittle star, Sea urchin, sand dollar Crustacean Gastropod, Bivalve, Cephalopod Echinoderm Arthropod Mollusk Shrimp, crabs, lobsters, barnacles, pill bugs, etc. Unique Features: Water vascular system Tube Feet Radial SymmetryBilateral Symmetry Unique Features: Jointed Limbs, chitin exoskeleton, Isopods make up 85% of all known species

3. Gastropod, Bivalve, Cephalopod Bivalve Examples: Oyster, mussels, clams, scallops, etc. Mollusk Cephalopod Examples: Squid, nautilus, octopus, cuttlefish Gastropod Examples: Snail, conch, sea hair, etc. Unique Features: No head, no radula Unique Features: Highly intelligent, nektonic, chromatophores, extremely well developed eye Unique Features: Changes in shell, advanced cephalization, torsion

4. Water vascular system – water flow throughout the organism that is used for movement, circulation, and diffusion • Tube feet – extensions from the WVS are hydraulic, used for movement, feeding, and respiration. • Radial Symmetry – anything round that can be evenly divided if split through a central point • Bilateral Symmetry – an organism that can be split on a longitudinal axis to create mirrored sides.

7. Asymmetry – an organism that cannot be evenly divided • Endoskeleton – calcium carbonate (CaCO3) skeleton found on the inside of the body (echinoderms) • Radial ring & canal – located in the central ring & on each arm used to control the WVS

8. Ambulacral groove – a groove in each arm of a sea star in which other anatomical parts can be found.

9. Ossicles– specialized bone (CaCO3) cells found within the endoskeleton of echinoderms • Echinoderm reproduction – defined genders, not hermaphroditic, can reproduce through regeneration if part of the central disc is in the segment • Sea Star vs. Brittle star movement – sea stars (much stronger) move slowly using all of the their feet. Brittle stars move in a serpentine fashion by dragging themselves behind a lead arm • Sea Urchins – lack arms, but possess tube feet, and extended poisonous spines

10. Sea cucumbers – lack spines, reduced endoskeleton, expels intestines as a defense mechanism • Respiratory tree – primitive gill-like tissue found on the outside of a sea cucumber • Crustaceans – subset of arthropods that live mostly in the water (shrimp, lobsters, crabs, barnacles) • Arthropod – “joint foot” • Chitin – a carbon-based molecule that makes up the exoskeleton of crustaceans

11. Isopod – land-based crustacean such as a pill bug (rolly polly) • % of known species that are arthropods – 85%

13. Exoskeleton – protective armor surrounding the outside of an organism such as an arthropod. It does not grow with the organism. • Molting – the process of shedding an old, too small exoskeleton, and re-growing a new exoskeleton. Crustaceans are most vulnerable during this time. • Hemolymph pump – a heart-like organ that pumps lymph through an open circulatory system • Open circulatory system – no veins or arteries, a disorganized movement of blood/lymph through the body

14. Crustacean nervous system – brain, ganglia, and dorsal nerve cord • Rounded eyes that can detect movement • Antenna that detects chemicals in the water • Tactile Hairs – located on claws & walking legs to assist in the detection of water movement, sand movement, and chemicals in the water • Statocyst – balance receptor • Thigmoreceptors – pressure sensors • Chemoreceptors – chemical sensors • Photoreceptors – light sensors

15. Crustacean Reproduction – defined genders, females have hair on the swimmerets to better hold eggs • Gastropod anatomy – next slide • Decapod – 10 legged organisms such as crustaceans (barnacle is the exception) • HAM – hypothetical primitive ancestor that has characteristics that appear among most members of the mollusk • Foot – muscular organ used for grasping & locomotion • Visceral mass – contains internal organs • Mantle – secretes CaCO3 for shell

17. Nacreous Layer – smooth inner layer of a shell that allows the gastropod to move in/out quickly without any cuts or abrasions • Duel function of gills – respiration & filter feeding • Radula – tissue covered in tooth-like protrusions that is used to scrape plant life off rocks • Nerve cord in mollusk – runs on the ventral side of most mollusks • Evolutionary innovations in gastropods – changes in shell, cephalization, torsion

18. Planospiral– ancient form of a gastropod shell in which the entire shell sits on top of the organism • Changes in the shell of gastropods – shells stick out to the side & shifts over so that the weight of the shell is better distributed

20. Cephalization – formation of a well-defined head region containing sensory organs, eyes, brain, mouth, etc • Torsion – embryonic process in which the shell of a gastropod spins 180 degrees • Advantages – head retracts first, gills are anterior, olfactory sensors & other sensory organs are anterior • Disadvantage - fouling • Fouling – the end of the digestive tract is anterior, causing waste to fall on the head and gills • Coelom – fluid-filled sack around the heart that protects the organ from shock/trauma

21. Columella – central axis that helps guide the formation of the shell • Operculum – a dense plate that closes over the aperture when a gastropod retreats within its shell

24. Nutrition of gastropods – mainly scavengers & herbivores, but some are active hunters/predators • Bivalves – “two-shells;” clams, oysters, mussels, scallops • No head, no radula • Adductor muscles – strong internal muscle that holds the shells of a bivalve together

26. Cephalopods – “head foot;” octopus, nautilus, squid, cuttlefish • Most intelligent invert • Most lack a shell • Active swimmers • Active predators • Chromatophores – color-changing cells • Specialization in feeding – • Powerful beak & radula • Tentacles & arms covered in suction cups and hooks • Siphon – • Cephalopod eyes & circulatory system –

27. Siphon – an opening near the head that draws water in & out for movement. The ink sac is located close to the siphon for defense • Cephalopod eyes & circulatory system – • Camera-type eye able to focus at multiple distances • The eye can quickly take in information and send it to the brain so that the chromatophores can quickly respond to a changing background • Closed circulatory system