Invertebrates Vocab Quiz Study Guide
(Definitions of all bold words from targets I and II)
By Matt Micucci, Vincent Fiorentini, and Anjali Pasupathy
Target I Words
Bilateral symmetry – The balanced distribution of duplicate body parts or shapes
Radial symmetry – Resemble a pie where several cutting planes produce roughly identical
pieces. Have only dorsal and ventral surfaces (top and bottom)
Protostome – Mouth to anus embryonic development from blastopore (arthropods,
nematodes, platyhelminthes, rotifers, mollusks, annelids)
Deuterostome – Anus to mouth embryonic development from blastopore (chordate,
echinoderms)
Acoelomate – No body cavity (Platyhelminthes: flatworms)
Pseudocoelomate – Full functional body cavity but is not nearly as organized as true
coelomates. Literally means “false cavity” (All pseudocoelomates are
protostomes but not all protostomes are pseudocoelomates. Ex:
Roundworm)
Coelomate – Fluid filled body cavity called a coelom with a complete lining derived from
mesoderm tissue (all vertabrates are coelomates)
Dipoblastic – 2 primary layers: ectoderm and endoderm. NO MESODERM.
Triploblastic – 3 primary layers: ectoderm, mesoderm, and endoderm
Ecdysozoans – arthropods, nematodes, and several smaller phyla (based on genetics)
Lophotrochozoans – a large group of Protostome animals (based on genetics)
Lophophore – a feeding organ in some aquatic organisms; a ring of ciliated tentacles around
mouth
Gas exchange – it’s different breathing in air than in water!
Gills – extract dissolved oxygen from water and then excrete carbon dioxide
Lungs – take in oxygen from the atmosphere and release carbon dioxide from the bloodstream
Dehydration – a very significant problem for land animals; adaptations to conserve water
Trochophore larva – free-swimming marine larva with several bands of cilia
Endoskeleton – an internal support structure composed of notochord and cartilage
Exoskeleton – an external support structure composed of chitin
Amniotic egg – an egg like the ones we studied in our last unit; amniotes are a group of
tetrapod vertebrates
Large body size – maybe reptile-like organisms had to stay small to conserve moisture (dunno)
Open circulatory system – No difference between blood and interstitial fluid: blood bathes the
organs directly
Closed circulatory system – Blood never leaves the network of blood vessel
Internal/external fertilization/development – review from previous units; hard to externally
fertilize (and somewhat develop) on land because it’s not covered in water
Jointed appendages – appendages that have joints, usually for walking.. yeah.
Target II Words
Sponges (Porifera)
Suspension feeders – “filter feeders”; feed by straining food particles from water. (porifera,
some cnidarians)
Spongocoel – The large, central cavity of a sponge.
Osculum – Opening through which water exits after passing through the spongocoel
Choanocyte –“Collar cells” that line the interior of the spongocoel. Help filter nutrients/food
from the water taken in from the collar of the sponge. Use phagocytosis to take in
food.
Mesohyl – Fills the space between the external and internal tissues of the sponge.
Amoebocyte – Mobile cell in echinoderms, mollusks and sponges etc. Defense against
pathogens. Equivalent to white blood cells in vertebrates.
Hermaphroditic – Containing both male and female reproductive organs
No distinct tissues – sponges have no distinct tissues
All words up to this point defined by Matt Micucci. 
Cnidarians
Gastrovascular cavity – the cavity in cnidaria and platyhelminthes for digestion and
nutrient distribution
Polyp – the plant-like stage of cnidarians, with the mouth/anus on top
Medusa – the jellyfish-like stage of cnidarians, with the mouth/anus on bottom
Cnidocyte – a cell with a coiled, barbed, poisonous thread to pwn stuff with
Nematocyst – the organelle that shoots the thing.
Marine – living in saltwater (oceans)
Freshwater – living in freshwater (lakes, streams, rivers, etc.)
Anemones – Finding Nemo predatory animals; pretty much only have a polyp stage
Jellies – jellyfish; when you picture them, that’s the medusa stage
Corals – the small, living polyps on a bunch of coral skeletons; mainly symbiotic relations
with photosynthetic unicellular algae
Flatworms (Platyhelminthes)
Protonephridia – remove metabolic wastes; dead-end tubules; like kidneys
Planarians – non-parasitic flatworms
Flatworms – no body cavity, no specialized circulatory or respiratory organs
Flukes – parasitic flatworms; eww. Don’t eat my liver.
Tapeworms – parasitic flatworms; lives in the digestive tract; does not have a gut
Roundworms (Nematoda)
Parasitic – inside organisms, like being heartworm
Free-living – often on the sea floor, eating detritus and stuff
Ecdysis – molting (shedding) the exoskeleton; think arthropods
Mollusks (Mollusca)
Muscular foot – remember that video with the mollusk running from the sea star? It had a muscular foot
Visceral mass – the body inside the mantle cavity; digestive, circulatory, excretory, and reproductive
Mantle – the (possibly shell-like) covering around the visceral mass; the fleshy stuff
Radula – the scary tongue-like thing used for feeding; schleeerrchhh
Gastropods (snails) – often have shells; univalves
Bivalves (clams, oysters, mussels, scallops) – shells are symmetrical on both sides; they filter feed
Cephalopods (squid, octopus) – have arms/tentacles and a prominent head
Siphon – the squid uses it to expel water (sucked into the mantle cavity) for super speed (locomotion)
Pen – the remnants of a shell in squids; made of chitin and functions like a backbone
Words from Cnidarians to here defined by Vincent Fiorentini :D
Segmented worms (Annelida)
Oligochaetes – A class of Annelida; name means few bristles; inhabit damp soil and fresh water;
includes earthworms
Segmented – Characteristic of Annelids; describes a body plan divided into distinct rings
Metanephridium – An excretory organ found in many invertebrates (including Annelida) that
typically consists of tubules connecting ciliated internal openings to external openings
Coelom – A body cavity lined by tissue derived of only mesoderm
Chaetae – Bristles made of chitin used for traction for locomotion and gas exchange; also called
setae
Arthropods (Arthropoda)
Hemolymph – Characteristic of an open circulatory system; a fluid that is propelled by a heart through
short arteries and into sinuses (spaces surrounding tissues and organs); the equivalent of blood
in a closed circulatory system
Spiders – A type of arachnid, of the subphylum Cheliceroformes, a part of Arthropoda; have clawlike
feeding appendages called chelicerae equipped with poison glands to attack prey; gas exchange
carried out by book lungs, stacked platelike structures in an internal chamber; construct webs of
silk to catch insects, escape quickly, cover eggs, courtship, and ballooning
Scorpions – type of arachnid, of the subphylum Cheliceroformes, a part of Arthropoda; have pedipalps
specialized for defense and capturing food; tip of tail bears poisonous stinger
Crabs – Of the subphylum Crustacea of the phylum Arthropoda; live in marine and freshwater
environments; is of a group of large crustaceans called decapods; some of these organisms that
live in the tropics also live on land
Lobsters – Of the subphylum Crustacea of the phylum Arthropoda; live in marine and freshwater
environments; is of a group of large crustaceans called decapods; have 19 pairs of appendages;
males use a specialized pair of abdominal appendages to transfer sperm to the female’s
reproductive pore
Chitin – A structural polysaccharide, consisting of amino sugar monomers, found in the exoskeletons of
all arthropods
Echinoderms
Water vascular system – In Echinoderms, a network of hydraulic canals branching into
extensions called tube feet
Tube feet – Numerous extensions of an Echinoderm’s water vascular system functioning in
locomotion, feeding, and gas exchange
Madreporite – A part of the water vascular system in Echinoderms; aids in communication
between the internal tubes with the exterior; regulates the amount of water in the
system
Ring canal – A part of the water vascular system in Echinoderms; in a sea star, a hard ring
around the mouth from which the radial canals extend
Gonads – In sea star, a pair of these are located in each ray, beneath the digestive glands; are
usually a deep brownish-red and tend to be smaller than the digestive glands
Ampulla – A part of a tube foot; bulb-like in shape; when this structure squeezes, it forces water
into the podium, expanding the podium and allowing it to make contact with the
substrate; water is forced back into this structure when the podium contracts
Radial canal – A part of the water vascular system of a sea star; runs in a groove down the down
the length of an arm; hundreds of tube feet branch from this structure
Digestive glands – These secrete digestive juices and help the organism to absorb and store
nutrients
Central disk – The structure within a sea star that contains a nerve ring and nerve cord
extending from the ring into the arms of the sea star
Deuterostomes – Animals characterized by a development in which the blastopore becomes the
anus, cleavage is radial, and the body cavity forms as outpockets of mesodermal tissue
Sea stars – Echinoderms that are part of the class Asteroidea; have arms radiating from a central
disk; the underside has tube feet used for movement, clinging to surfaces, and grasping
prey; consumes food by ejecting a part of its stomach and digesting its prey, such as
bivalves, where they are; some can regenerate lost arms or even entire organisms when
fractured
Sea urchins – Echinoderms that are part of the class Echinoidea; have five rows of tube feet used
for slow movement; have muscles that pivot their spines for protection and
movement; have a complex, jawlike structure to eat seawed; are roughly spherical
Sea cucumbers – Echinoderms that are part of the class Holothuroidea; have elongated in their
oral-aboral axis, lack spines, and have a reduced endoskeleton; have five rows of tube
feet used in locomotion; the tube feet around the mouth may act as feeding tentacles
Words from Annelida to here defined by Anjali Pasupathy