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Phylum Mollusca• Means “soft”…refers to their bodies• Are coelemates…three body layers
with true body cavity• Two body parts:
– Head-foot…travels on and has sensory organs
– Visceral mass…organs• Body covered by mantle (and often a
shell)• Bilateral symmetry
Phylum Mollusca• Systems:
– Complete digestive system
– Separate sexes, external fertilization (some hermaphrodites)
– Breathe through gills
– Open circulation (hemolymph)
Phylum Mollusca
Phylum Mollusca• Radula:
“tongue” structure covered with
“teeth” (made of chitin) scrape food.
Phylum Mollusca•3 Classes
–Gastropoda–Bivalvia–Cephalopoda
Class Gastropoda• “stomach-foot”… crawls on
“stomach”• Snails, slugs, conch• Visceral mass turns 180o so
organs exit out front (torsion)• All are motile
Class Gastropoda
Nudibrach
Class Bivalvia• 2 halves (valves) to the shell• Clams, mussels, oysters, scallops• Most are sessile and filter feed• No head or brain, 3 pairs of
ganglia• Separate sexes, external
fertilization (most)
Class Bivalvia
Class Cephalopoda• “head foot” travel around head
first, tentacles• Octopi, squid, cuttlefish, nautilus• Most advanced nervous system of
any mollusk…lobes, complex eyes• Closed circulatory system (more
advanced…move faster)• Separate sexes, internal fertilization• Chromatophores (change color), ink
http://www.youtube.com/watch?v=zjycOCyUZ1c
Phylum Echinodermata• “spiny skin”• Sea stars, sand dollars, sea urchins,
sea cucumbers• Radial symmetry (bilateral larva)• No cephalization• Ossicles (endoskelton)• Water-vascular system (not blood or
hemolymph)• Tube feet (water filled … suction)
Tube feet
Class Crinoidea
e.g. crinoids, sea lillies, feather stars
Class Ophiuroidea
e.g. brittle stars and basket stars
Class Echinoidea
e.g. sea urchins, sand dollars
Class Holothuroidea
e.g. sea cucumber
Class Asteroidea• “star like”• Sea stars (star fish)• Oral/aboral side (mouth/not mouth)• Uses water in tubes through body for
circulation (water-vascular system)
• 2 stomachs…one goes out of body• Nerve ring, radial nerve down each
arm, eye spot (light)• Separate sexes, external fertilization
Phylum Arthropoda• “jointed foot”• Segmented animals with
appendages (“arms/legs”)• Exoskeleton for protection and
support• Molt when they grow (shed exo.)• Highly cephalized…compound eye,
antennae, brain• Open circulatory system
(hemolymph)
Subphylum Crustacea• Very diverse … only 1 characteristic
in common … 2 pairs of antennae• Most:
– Mandible (jaws)– 1 pair of appendages per segment– Segments fused together– Some breathe with gills, some through
holes in exoskeleton– Indirect development (larval stage
naupilus)
Crayfish• Decapod … “10 feet”• 2 body parts:
– Cephalothorax (head, 5 segments, thorax)
– Abdomen
• Antennae (long … touch, taste)• Antennules (short … touch,
taste, balance)
Crayfish• Mandibles to chew
– Maxillae and maxillipeds to manipulate food
• Walking legs, pinchers, swimmerets• Complete digestive system• Gills (legs make currents)• Open circulatory system• Green gland for waste• Brain
Subphylum Crustacea
Subphylum Chelicerata and Myriapoda
• Chelicerata includes spiders, scorpions, mites, horseshoe crabs, ticks
– Have special mandibles called chelicera
– Special lungs called book lungs
• Myriapod (“many feet”)– Millipedes and centipedes
Subphylum Chelicerata
Subphylum Myriapoda
Class Insecta• Insects…technically only 1 order
(Hemiptera) are bugs• Segmented bodies (3 parts)
– Head, thorax, abdomen
• Exoskeleton (breathe through holes in exoskeleton)
• Jointed legs (3 parts)
Order Hemiptera• Bugs
• Damage crops, spread disease
Order Hemoptera
• Aphids, cicadas
• Damage crops, young trees
Order Isoptera• Termites• Damage wood in
buildings • Recycle wood in
forests
Order Odonata
• Dragonflies, damselflies
• Destroy harmful insects
• Nymphs are food
Order Orthoptera• Grasshoppers,
crickets, preying mantis
• Damage crops • Eats pests
Order Coleoptera• Weevils, beetles,
ladybugs
• Damage crops, trees
• Eat other insects
Order Diptera
• Mosquitoes, flies, gnats
• Carry disease, destroy crops
• Pollinate flowers, decompose
Order Hymenoptera• Bees, wasps,
ants
• Pollinate flowers, honey, destroy pests
• Sting
Order Lepidoptera• Butterflies,
moths
• Pollinate flowers, make silk
• Larva damage crops
Incomplete metamorphosi
s• Direct
development• Young look like
adult, except smaller and often without wings
• Young are called nymphs.
• Often several molts (shed exoskeleton) to become adult
Complete Metamorphosis
• Indirect development
• Young do not look like adult
• Often involves a cocoon (chrysalis) and inside is a larva called a pupa.
