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

http://24.248.120.104/caveman/scorpion.jpg

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.