WORMS!!!!!WORMS!!!!!Phylum Platyhelminthes

Phylum NemerteaPhylum NematodaPhylum Annelida

Bilateral SymmetryBilateral SymmetryArrangement of body parts in such a

way that there is only one way to cut the body and get two identical halves

OrientationOrientationAnterior – frontPosterior – rear

or backDorsal – backVentral - belly

Bilateral Charact.Bilateral Charact.Bilateral symmetry allows for the

following:- A head with a brain- More active pursuit of prey- Body has specialized tissues and

organs- More sophisticated behaviors

Phylum PlatyhelminthesPhylum Platyhelminthes “Flatworms” Dosrsoventrally

flattened (flat backs and bellies)

Simplest organisms whose tissues are organized into real organs and organ systems

Phylum PlatyhelminthesPhylum Platyhelminthes Has a central

nervous system with a simple brain and nerve cords along the body

There is a well developed muscular system, reproductive, and digestive system

Phylum PlatyhelminthesPhylum Platyhelminthes

a) Can be carnivorous

b) Can live inside or on the surface of organisms

c) Parasites such as flukes and tapeworms

Phylum NemerteaPhylum Nemertea“Ribbon

worms”Look like long

flat wormsOne measured

at 30m long

Phylum NemerteaPhylum NemerteaDefining characteristics:

• Complete digestive tract: mouth, gut, anus

• Presence of a circulatory system

• Most distinctive feature is a probiscus

• All predators that feed on worms and crustaceans

ProboscusProboscusA long, fleshy

tube used to entangle prey

Everted from a cavity above the mouth like a finger in a glove

Phylum NematodaPhylum Nematoda “Roundworms” or

Nematodes Live in sediments

or the tissues of other organisms (parasites)

Slender, cylindrical bodies are typically pointed at both ends

Phylum NematodaPhylum NematodaHydrostatic skeleton that

provides support and locomotion

Larva can be found in raw fish which is in turn ingested by humans

Phylum AnnelidaPhylum Annelida “Segmented

Worms” Body consists of a

series of segments (think earthworm)

Gut goes through all segments

Contain a central cavity known as a coelom

Phylum AnnelidaPhylum AnnelidaClosed circulatory system –

blood always stays in blood vessels

Typically burrowersIncludes Leeches