Unit #5 Exam Review
Echinoderms, Crustaceans, and
Mollusks
Echinoderm
Sea star, brittle star,
Sea urchin, sand dollar
Unique Features:
Water vascular system
Tube Feet
Radial Symmetry
Bilateral Symmetry
Arthropod
Crustacean
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
Mollusk
Bivalve Examples:
Oyster, mussels,
clams, scallops, etc.
Unique Features:
No head, no radula
Gastropod,
Bivalve,
Cephalopod
Gastropod Examples:
Snail, conch, sea
hair, etc.
Unique Features:
Changes in shell,
advanced cephalization,
torsion
Cephalopod Examples:
Squid, nautilus, octopus,
cuttlefish
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 (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 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 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
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