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