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PHYLUM PLATYHELMINTHES
(PLAT –EE- HELL-MIN – THEEZ)
FLATWORMS
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.
Phylum Platyhelminthes
• Flat Worms –dorsoventrally (back to front) flattened
• swims by undulations of the body
• Flatworms are the simplest animals in which tissues are organized into real organs and organ systems
This Phylum’s Advance
• Bilateral symmetry
• 3 tissue layers (ectoderm, mesoderm, endoderm) = triploblastic
• Cephalization – formation of a head and “Brain”
• Nerve ladder
• Still only one opening in the gut
Flat wormCephalization
Simple yet Colorful
Just a few Examples
You can see why they are called Flatworms
The Biology of Flatworms
Cephalization refers to the formation of a
A. Head and Tail
B. Head and “Brain”
C. Anus
D. Mouth
Head an
d Tail
Head an
d “Brai
n”
Anus
Mouth
25% 25%25%25%
Platyhelmithes is the first phylum to have….
A. A nerve net
B. Cephalization
C. Tissues
D. An Anus
A nerve n
et
Cephaliza
tion
Tissu
es
An Anus
25% 25%25%25%
Flatworms have ____ tissue layer(s).A. 1
B. 2
C. 3
D. 4
1 2 3 4
25% 25%25%25%
What type of Symmetry do Flatworms have?
A. Bilateral
B. Radial
C. Asymmetry
D. Spacial
Bilate
ral
Radial
Asymm
etry
Spacia
l
25% 25%25%25%
Fastest RespondersSeconds Participant Seconds Participant
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
• HERMAPHRODITIC.
• SEXUAL ONLY• TAPEWORMS CAN
POSSIBLY SELF-FERTILIZE.
H. DIGESTIVE SYSTEM
Class Feeding Digestion
TURBELLARIANS FEED ON SMALL INVERTEBRATES
Mout h is used f or bot h ingest ion & exc r et ion.
Mout h l eads t o phar ynx and is f ol l owed by t he gut
Cest odes FEED ON HOST (INTESTINE OF A VERTEBRATE ANIMAL)
P ossess no gut or simpl e gut No mout h or digest ive t r ac t
Absor b f ood f r om envir onment Digest ion is int r acel l ul ar
Tr emat odes FEED ON HOST TISSUE THROUGH P HARYNX.
Cont ain mout h and simpl e gut Digest ion is ext r acel l ul ar and
t hen int r acel l ul ar
H. DIGESTIVE SYSTEM
1. ONE OPENING - THE MOUTH
2. PHARYNX AND INTESTINES.
3. TAPEWORMS DO NOT NEED A DIGESTIVE SYSTEM.
I. LIFE CYCLES
TAPEWORMCP 25
I. LIFE CYCLES
FLUKECP 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!!!