Porifera
Platyhelminthes
Annelida
Major Classes
Hexactinellida, Demospongia, Calcarea
Tuberellaria – planarians carnivores, prey on
smaller animals/dead animals
Monogenea, Trematoda, Cestoidea
Species Examples
Sponge (Callyspongia plicifera), Sycon coactum,
ascute ascanoides
n/a
n/a
 No true tissues
 2 layers of cells separated by mesohyl
No
No
 Regeneration/replacement of body parts
Dugesia; Planaria; tapeworm; flukes
Oligochaeta (reduced head, no parapodia:
earthworms, eats soil & extracts nutrients),
Polychaeta (pair of parapodia on each segment,
mostly marine), Hirudinea (suckers at ends, no
tentacles, parapodia: leeches, fresh water, blood
sucking parasites)
Earthworm, Lumbrious terrestris, Hirudo
medicinaiis
 Some free living; parasitic w/ complex life
cycles
Movement
 Filter feeder
 Home for small marine plants
 Recycle Ca by digesting reefs & mollusks
 Mostly marine, some freshwater
Porocytes – cells that allow water to enter the
spongocoel
Spongocoel – central cavity
Mesohyl – gelatinous matrix, separates the two
layers of cells
Osculum – larger opening at top of spongocoel
Choanocyte – cells with flagella that propel the
water; ingest food particles by phagocytosis
Amoebocyte – wandering cells with pseudopodia
that take up food from water, digest it, transport
neutrients
Spicules – skeletal fibers; structure & support
 Most hermaphrodites
 Fertilization & development in mesophyl
 Reproduce asexually by broken fragments
Sessile
Related Diagrams
Figure 33.3
Symmetry Type
# of germ layers
Body Plan
Cephalization
Coelom
Developmental
Characteristics
Nutrition/
Ecological Role
General Habitat
Unique Anatomical
Features
Reproduction
Bilateral
Triploblastic
 Some cephalization
 Gastrovascular cavity
Eyespots; central ganglion
No
 Protostome
Marine, fresh water; damp terrestrial
Pharynx – muscle that sucks food into the
gastrovascular cavity
Gastrovascular cavity –central digestive
compartment
Scolex – distributes food throughout
Proglottids – sex organ sacs
 Sexual hermaphrodites
 Asexual regeneration
 Internal fertilization/development
 Use cilia to glide on secreted mucus
 Muscles can be used
Figure 33.10, 33.11; Table 33.2
Bilateral
Triploblastic
 series of fused rings
Yes
Yes
 Protostome
 Digestive system w/ pharynx, esophagus, crop,
gizzard, intestine
 Coelom used for storage/complex organ dev.
 Hirudina can be parasite, predators, scavengers
 Earthworms improve soil conditions
 Leeches used to treat bruised tissues
Sea, freshwater, damp soil
 metanephridia – pair of excretory tubes
 cerebral ganglia – brain like structure
 Segmentation – specialization of body regions;
coelom partitioned by septa
 Peristalsis: contracting of muscles that allows
food to move through digestive tract
 Sexual hermaphrodites
 Internal fertilization; external development
motile
Figure 33.23; Table 33.4
Major Classes
Species Examples
Mollusca
Echinodermata
Polyplacophora, Gastropoda –spiral shell, torsion(
visceral mass rotates up 180°, anus & mantle
cavity above head) Bivalvia –shell w/ 2 halves,
reduced head, paired gills, filter feeder,
cephalopoda –head surrounded by tentacles,
speedy, closed circulatory sys., complex nervous
sys, brain, sensory organs
Snails, slugs, oysters, clams, octopuses, squid
Tridacna maxima, Helix aspersa, Enteroctopus dotleini
Asteroidea, Ophiuroidea, Echinoidea, Crinoidea,
Holothuroidea
Symmetry Type
Bilateral
# of germ layers
Body Plan
Triploblastic
See unique anatomical features
Cephalization
Coelom
Developmental
Characteristics
Nutrition/
Ecological Role
General Habitat
Unique Anatomical
Features
Yes, in some classes
Yes
 Trochophore – ciliated larva stage
 Mostly soft bodied w/ hard shell
 Cephalopoda are carnivores
Reproduction
 Sexual
 Fertilize: water/female’s mantle cavity
 Develop: water/seafloor
Muscular foot, cephalopoda use jet propulsion
(water drawn by mantle cavity)
Figure 33.16, 33.18, 33.21; Table 33.3
Movement
Related Diagrams
Marine; some fresh water; some land
 Muscular foot – movement & stability
 Visceral mass – contains int. organs
 Mantle – fold of tissue over visceral mass;
secretes shell
 Mantle Cavity – houses gills, filled w/ water
 Radula – near mouth; used to scrape up food
Sea star, sea urchin, sea cucumber, sea lily
Oritireaster linckii, caulerpa racemosa, echincthrix
calamaris
Bilateral (adult radial appearance is 2nd adaptation
to sessile lifestyle)
Triploblastic
 Thin skin covers endoskeleton
 Water vascular system

No
Yes
 Deuterostome
 Metamorphosis from bilateral larvae
Some carnivores,
Marine
 Water vascular system
 hydraulic canals branch into tube feet; used for
movement, feeding, gas exchange
 pedicellaria – keeps debris off boyd surface,
protects skin gills
 skin gills
 dermal papillae
 open circulatory system
 Sexual
 External fertilization/development
 Asexual Regeneration
Some are sessile
Figure 33.38
Nematoda
Caenorhabitis elegans; hookworms, pinworms
Trichinella spiralis
Bilateral
Triploblastic
 Cuticle covering epidermal cells
 Longitudinal muscle cells
Yes
Pseudocoelom
Protostome
Decomposers, nutrient cycling, parasite,
grow/reproduce in humans
Aquatic, wet soil, moist tissues of plants
 Fine tip at posterior end; blunt tip at head
 Sexual
 internal fertilization; external development
longitudinal muscles = whip like motion
Major Classes
Species Examples
Symmetry Type
# of germ layers
Body Plan
Cephalization
Coelom
Developmental
Characteristics
Nutrition/
Ecological Role
General Habitat
Unique Anatomical
Features
Arthropoda
Cnidaria
Aracnida (6 pairs of appendages, chelicerae, pedipalps,walking legs,
usesilk) Crustacea (19 appendage pairs, 2 antennae pairs) Insecta (flies,
tracheal system, incomplete metamorphasis), Chilopoda (pair of antannea,
3 pairs of mouth parts, poison claws), Diplopoda (many legs)
Apis mellifica, Aculepeira cerapegia, Trigoniulus corallinus
Bilateral
Triploblastic
 segmentation, hard exoskeleton, jointed appendages
 completely covered by cuticle (exoskeleton)
Yes
Yes
 molting – sheds old exoskeleton to grow a new one; vulnerable during
this time
 metamorphosis – complete change of form (insects, ex. Caterpillar →
butterfly)
 incomplete metamorphosis – young resemble adults (ex. Grasshopper)
 Some parasites, some carnivores, some decomposers
 Centipedes – carnivores
Mainly land, some water, under your couch
Proglottids – flattened segments, important for repro.
Mandibles – jawlike structure
Sensory antennae
Compound eyes – many eyes w/ separate focuses
Book lungs (spiders) – stacks of plates for gas exchange
Malpighian tubules – removes metabolic wastes in insects
Tracheal system – gas exchange in insects
Hydrozoa – alternate polyp/medusa form; alternate (a)sexual w/ budding
Scyphozoa – medusa primary; live as jellies
Anthozoa – only polyps; each polyp built on remains of previous
Reproduction
 Asexual & sexual (usually sexual)
 Internal fertilization; external development
Movement
Related Diagrams
Legs, wings,
Figure 33.26, 33.30, 33.33; Table 33.5
Related source: www.geocities.com/mrsfranksbiology/invertanimalanswers.doc
Anemone; jellyfish; coral; hydra
Radial
Diploblastic
 Have true tissues
 Gastrovascular cavity
No
No
 Polyp or medusa
 Carnivore; uses cnidcytes to capture prey & for defense
Mostly marine
 Polyps – cylindrical form, adheres to substratum; tentacles that
capture/push prey into mouth
--Or—
 Medusa – upside down motile polyp
Gastrovascular cavity –central digestive compartment
 Nematocysts: cnidocytes that sting & release venom
 Sac with gastrovascular cavity
 Epidermis – outer cell layer; provides protection
 Gastrodermis – inner cell layer; used for digestion
 Cnidocytes – cells on tentacles used for defense & prey
 Mesoglea – jelly substance that makes up body; structural support
 Nematocytes – stinging capsule organelle
 Nerve net – simple nervous system; enables organisms to respond to
physical contact
 Sexual hermaphrodites
 External fertilization/development
 Asexual budding
Polyps = sessile; medusa = motile
Figure 33.4, 33.5; Table 33.1
Related Diagrams/Tables
Phylum Porifera
33-03-SpongeAnatomy-L
33-05-HydraCnidocyte-L
Phylum Cnidaria
Table 33-1. Classes of Phylum Cnidaria
Class and Examples
Hydrozoa (Portuguese man-of-war,
hydras, Obelia , some corals) (see
FIGURES 33.6a and 33.7)
Scyphozoa (jellies, sea wasp, sea nettle)
(see FIGURE 33.6b)
Anthozoa (sea anemones, most corals, sea
fans) (see FIGURE 33.6c and d)
33-04-CnidarianForms-L
Main Characteristics
Most marine, a few freshwater; both
polyp and medusa stages in; most species;
polyp stage often colonial
All marine; polyp stage reduced; freeswimming; medusas up to 2 m in
diameter
All marine; medusa stage completely
absent; sessile, many colonial
Phylum Plathelminthes
Table 33-2. Classes of Phylum Platyhelminthes
Class and Examples
Turbellaria (mostly free-living
flatworms; e.g., Dugesia ) (see
FIGURE 33.9 and 33.10)
Monogenea (monogeneans)
Trematoda (trematodes, also
called flukes) (see FIGURE
33.11)
Cestoidea (tapeworms) (see
FIGURE 33.12)
33-10-PlanarianAnatomy-L
Main Characteristics
Most marine, some freshwater, a
few terrestrial, predators and
scavengers; body surface ciliated
Marine and freshwater parasites;
most infect external surfaces of
fishes; life history simple; a
ciliated larva starts an infection
on a host
Parasites, almost always of
vertebrates; two suckers attach to
host; most life histories include
intermediate hosts
Parasites of vertebrates; scolex
attaches to host; proglottids
produce eggs and break off after
fertilization; no head or digestive
system; life history with one or
more intermediate hosts
33-11-BloodFlukeLifeHist-L
Phylum Mollusca
Table 33-3. Major Classes of Phylum Mollusca
Class and Examples
Polyplacophora
(chitons)(see FIGURE
33.17)
Gastropoda (snails,
slugs) (see FIGURES
33.18 and 33.19)
33-16-MolluskBodyPlan-L
33-18-GastropodTorsion-L
Bivalvia (clams, mussels,
scallops, oysters) (see
FIGURES 33.20 and
33.21)
Cephalopoda (squids,
octopuses, chambered
nautiluses) (see FIGURE
33.22)
Main Characteristics
Marine; shell with eight plates; foot used for
locomotion; head reduced
Marine, freshwater, or terrestrial; asymmetric
body, usually with a coiled shell; shell reduced
or absent in some; foot for locomotion; radula
present
Marine and freshwater, flattened shell with two
valves; head reduced; paired gills; most are
filter-feeders; mantle forms siphons
Marine; head surrounded by grasping tentacles,
usually with suckers; shell external, internal, or
absent; mouth with or without radula;
locomotion by jet propulsion using siphon made
from mantle
Phylum Mollusca cont’d
Phylum Echinodermata
33-21-ClamAnatomy-L
33-38-SeaStarAnatomy-L
Phylum Annelida
Table 33-4. Classes of Phylum Annelida
Class and Examples
Oligochaeta (terrestrial and freshwater
segmented worms; e.g., earthworms) (see
FIGURES 33.23 and 33.24a)
Polychaeta (mostly marine segmented
worms) (see FIGURE 33.24b and c)
Hirudinea (leeches) (see FIGURE 33.24d)
Main Characteristics
Reduced head; no parapodia, but setae present
Well-developed head; each segment usually has
parapodia with setae; tube-dwelling and freeliving
Body usually flattened, with reduced coelom
and segmentation; setae absent; suckers at
anterior and posterior ends; parasites,
predators, and scavengers
33-23-EarthwormAnatomy-L
Phylum Atrhropoda
33-26-ArthropodExtAnatom-L
33-33-InsectAnatomy-L
33-30b-SpiderAnatomy-L
Table 33-5. Some Major Arthropod Classes (based on a traditional taxonomy that places all
arthropods in a single phylum, Arthropoda)
Class and Examples
Main Characteristics
Arachnida (spiders, scorpions, Body having one or two main parts; six pairs of
ticks, mites)
appendages (chelicerae, pedipalps, and four pairs of
walking legs); mostly terrestrial
Diplopoda (millipedes)
Body with distinct head bearing antennae and
chewing mouthparts, segmented body with two pairs
of walking legs per segment; terrestrial; herbivorous
Chilopoda (centipedes)
Body with distinct head bearing large antennae and
three pairs of mouthparts; appendages of first body
segment modified as poison claws; trunk segments
bear one pair of walking legs each; terrestrial;
carnivorous
Insecta (insects)
Body divided into head, thorax, and abdomen;
antennae present; mouthparts modified for chewing,
sucking, or lapping; usually with two pairs of wings
and three pairs of legs; mostly terrestrial
Crustacea (crabs, lobsters,
Body of two or three parts; antennae present; chewing
crayfish, shrimp)
mouthparts; three or more pairs of legs; mostly
marine
Other Invertebrate Diagrams
33-07-HydrozoanLifeCycle-L3
33-36-SegmentationOrigin-L