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

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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

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Flatworms have ____ tissue layer(s).A. 1

B. 2

C. 3

D. 4

1 2 3 4

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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!!!