Unit #5 Exam Review Echinoderms, Crustaceans, and Mollusks

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

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

2)Water vascular system – water flow throughout the organism that is used for movement, circulation, and diffusion 2)Tube feet – extensions from the WVS are hydraulic, used for movement, feeding, and respiration. 3)Radial Symmetry – anything round that can be evenly divided if split through a central point 4)Bilateral Symmetry – an organism that can be split on a longitudinal axis to create mirrored sides.

6)Asymmetry – an organism that cannot be evenly divided 7)Endoskeleton – calcium carbonate (CaCO 3 ) skeleton found on the inside of the body (echinoderms) 8)Radial ring & canal – located in the central ring & on each arm used to control the WVS

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

10) Ossicles – specialized bone (CaCO 3 ) cells found within the endoskeleton of echinoderms 11) Echinoderm reproduction – defined genders, not hermaphroditic, can reproduce through regeneration if part of the central disc is in the segment 12) 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 13) Sea Urchins – lack arms, but possess tube feet, and extended poisonous spines

14) Sea cucumbers – lack spines, reduced endoskeleton, expels intestines as a defense mechanism 15) Respiratory tree – primitive gill-like tissue found on the outside of a sea cucumber 16) Crustaceans – subset of arthropods that live mostly in the water (shrimp, lobsters, crabs, barnacles) 17) Arthropod – “joint foot” 18) Chitin – a carbon-based molecule that makes up the exoskeleton of crustaceans

19) Isopod – land-based crustacean such as a pill bug (rolly polly) 20) % of known species that are arthropods – 85%

30) Exoskeleton – protective armor surrounding the outside of an organism such as an arthropod. It does not grow with the organism. 31) Molting – the process of shedding an old, too small exoskeleton, and re-growing a new exoskeleton. Crustaceans are most vulnerable during this time. 32) Hemolymph pump – a heart-like organ that pumps lymph through an open circulatory system 33) Open circulatory system – no veins or arteries, a disorganized movement of blood/lymph through the body

34) Crustacean nervous system – brain, ganglia, and dorsal nerve cord Rounded eyes that can detect movement Antenna that detects chemicals in the water 35) Tactile Hairs – located on claws & walking legs to assist in the detection of water movement, sand movement, and chemicals in the water 36) Statocyst – balance receptor 37) Thigmoreceptors – pressure sensors 38) Chemoreceptors – chemical sensors 39) Photoreceptors – light sensors

40) Crustacean Reproduction – defined genders, females have hair on the swimmerets to better hold eggs 41) Gastropod anatomy – next slide 42) Decapod – 10 legged organisms such as crustaceans (barnacle is the exception) 43) HAM – hypothetical primitive ancestor that has characteristics that appear among most members of the mollusk 44) Foot – muscular organ used for grasping & locomotion 45) Visceral mass – contains internal organs 46) Mantle – secretes CaCO 3 for shell

47) Nacreous Layer – smooth inner layer of a shell that allows the gastropod to move in/out quickly without any cuts or abrasions 48) Duel function of gills – respiration & filter feeding 49) Radula – tissue covered in tooth-like protrusions that is used to scrape plant life off rocks 50) Nerve cord in mollusk – runs on the ventral side of most mollusks 51) Evolutionary innovations in gastropods – changes in shell, cephalization, torsion

52) Planospiral – ancient form of a gastropod shell in which the entire shell sits on top of the organism 53) Changes in the shell of gastropods – shells stick out to the side & shifts over so that the weight of the shell is better distributed

54) Cephalization – formation of a well-defined head region containing sensory organs, eyes, brain, mouth, etc 55) 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 56) Fouling – the end of the digestive tract is anterior, causing waste to fall on the head and gills 57) Coelom – fluid-filled sack around the heart that protects the organ from shock/trauma

58) Columella – central axis that helps guide the formation of the shell 59)Operculum – a dense plate that closes over the aperture when a gastropod retreats within its shell

63) Nutrition of gastropods – mainly scavengers & herbivores, but some are active hunters/predators 64) Bivalves – “two-shells;” clams, oysters, mussels, scallops No head, no radula 65) Adductor muscles – strong internal muscle that holds the shells of a bivalve together

66) Cephalopods – “head foot;” octopus, nautilus, squid, cuttlefish Most intelligent invert Most lack a shell Active swimmers Active predators 67) Chromatophores – color-changing cells 68) Specialization in feeding – Powerful beak & radula Tentacles & arms covered in suction cups and hooks 69) Siphon – 70) Cephalopod eyes & circulatory system –

69) Siphon – an opening near the head that draws water in & out for movement. The ink sac is located close to the siphon for defense 70) 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