Unit #5 Exam Review

Echinoderms, Crustaceans, and Mollusks

Echinoderm ArthropodMollusk

Sea star, brittle star,Sea urchin, sand dollar

Crustacean Gastropod, Bivalve, Cephalopod

Unique Features:Water vascular systemTube Feet

Radial SymmetryBilateral 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

3) Tube feet – extensions from the WVS are hydraulic, used for movement, feeding, and respiration.

4) Radial Symmetry – anything round that can be evenly divided if split through a central point

5) 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 (CaCO3) 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 (CaCO3) 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 receptor37) Thigmoreceptors – pressure sensors38) Chemoreceptors – chemical sensors39) Photoreceptors – light sensors

40) Crustacean Reproduction – defined genders, females have hair on the swimmerets to better hold eggs

41) Gastropod anatomy – next slide42) 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 organs46) Mantle – secretes CaCO3 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 feeding49) Radula – tissue covered in tooth-like protrusions

that is used to scrape plant life off rocks50) Nerve cord in mollusk – runs on the ventral side

of most mollusks51) 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 cells68) 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