PHYLUM
PLATYHELMINTHES
(PLAT –EE- HELL-MIN – THEEZ)
FLATWORMS
PLEASE PREPARE TO TAKE
NOTES.
A. THE MAJORITY OF FLATWORMS ARE PARASITES.
B. THE GATEWAY PHYLUM TO
THE REST OF THE ANIMAL
KINGDOM.
CNIDARIANS:
• RADIAL
SYMMETRY
• TWO LAYERS
• LACKING MOST
ORGAN SYSTEMS.
FLATWORMS:
• BILATERAL SYMMETRY
• THREE LAYERS
• CENTRALIZED NERVOUS
SYSTEM
• SIMPLE EXCRETORY
SYSTEM.
• COMPLEX REPRODUCTIVE
SYSTEM.
• SIMPLE DIGESTIVE
SYSTEM.
C. THREE CLASSES
C. THREE CLASSES
1. TURBELLARIA MADE UP OF MOSTLY
FREE LIVING
FLATWORMS. CAN
LIVE IN MARINE,
FRESHWATER, AND
DAMP TROPICAL
ENV.
• EXAMPLES:
PLANARIA
AND
POLYCLADIDS.
C. THREE CLASSES
2. TREMATODA –
KNOWN AS
FLUKES. ALL
ARE PARASITIC
AND VERY
DAMAGING.
• EXAMPLES:
ASIAN LIVER
FLUKE AND
SCHISTOSOMES.
C. THREE CLASSES
3. CESTODA –
KNOWN AS
TAPEWORMS.
ALL ARE
PARASITIC.
• EXAMPLES:
PORK, BEEF,
FISH, & DOG
TAPEWORMS.
D. THREE LAYERS
1. EPIDERMIS –
TOUGH (Outer
Layer)
2. MUSCLE –
CIRCULAR
AND
LONGITUDINAL
3. MESENCHYME
(Connective
Tissue)
E. NERVOUS SYSTEM
• SIMPLE BRAIN
FOUND AT THE
HEAD END.
• TWO NERVE
CORDS THAT
LOOK LADDER
LIKE.
F. EXCRETORY SYSTEM
• CONTAINS
FLAME CELLS.
(THE CILIA LOOKS
LIKE A
FLICKERING
FLAME)
G. REPRODUCTIVE
SYSTEM
• HERMAPHRODI
TIC.
• SEXUAL ONLY
• TAPEWORMS
CAN POSSIBLY
SELFFERTILIZE.
H. DIGESTIVE SYSTEM
C la s s
F e e d in g
D ig e s tio n
T U R B E L L A R IA N S
FEED ON SM ALL
IN V E R T E B R A T E S
 M o u t h is u s e d f o r b o t h in g e s t io n
& e x c r e t io n .
 M o u t h l e a d s t o p h a r y n x a n d is
follow ed by th e g ut
C estodes
FEED ON HOST
(IN T E S T IN E O F A
VERTEBRATE
A N IM A L )
 P o s s e s s n o g u t o r s im p l e g u t
 N o m o u t h o r d ig e s t iv e t r a c t
 A b s o r b f o o d f r o m e n v ir o n m e n t
 D ig e s t io n is in t r a c e l l u l a r
Trem atodes
FEED ON HOST
T IS S U E T H R O U G H
PHARYNX.
 C o n t a in m o u t h a n d s im p l e g u t
 D ig e s t io n is e x t r a c e l l u l a r a n d
t h e n in t r a c e l l u l a r
H. DIGESTIVE SYSTEM
1. ONE OPENING THE MOUTH
2. PHARYNX AND
INTESTINES.
3. TAPEWORMS DO
NOT NEED A
DIGESTIVE
SYSTEM.
I. LIFE CYCLES
TAPEWORM
CP 25
I. LIFE CYCLES
FLUKE
CP 23
J. MISC.
1. THEY DO NOT
HAVE A
CIRCULATORY
SYSTEM OR A
RESPIRATORY
SYSTEM. USE
DIFFUSION.
J. MISC.
2. CONSIDERED ACOELOMATES
BECAUSE THEY LACK A BODY
CAVITY.
3. HAVE A HYDROSTATIC
SKELETON.
4. THEY ARE REALLY FLAT!!!
ANY QUESTIONS???