Phylum Platyhelminthes“Flat Worms”

By Mrs. Farkhandah Shareef

TriploblasticHaving a body derived from three embryonic cell layers (ectoderm, mesoderm, and endoderm), as in all multicellular animals except sponges and coelenterates.

Triploblastic Acoelomate Body Plana:

EVOLUTIONARY PERSPECTIVE

Members of the phyla are:

(a) Phylum Platyhelminthes:(b) Phylum Nemertea:(c) Phylum Gastrotricha:

Platyhelminthes

Platy = flat

Helminthes = worm

Flat Worms

There are four classes of flatworms, three of which are important to us…

Platyhelminthes

Class: Turbellaria – planaria

Class: Cestoda – tapeworms

Class: Trematoda – flukes

Size range:

Their size ranges from few millimeters (10 mm in case of planaria) to several meters (tapeworm).

Digestive system

Excretory system

There are two types of reproduction; asexual reproduction

sexual reproduction

Reproductive System

and Reproduction

Example of Platyhelminthes Animals

Characteristics

1. Triploblastic

a) Ectoderm (epidermis)b) Mesodermc) Endoderm

Flatworms 3 cell layers:

2. Linear nervous system with a ganglion (brain)

Characteristics

3. Dorsoventrally flat, bilaterally symmetrical body

Characteristics

4. Cephalization – the development of an anterior end

Characteristics

5. Incomplete digestive system (one opening)6. An excretory system for removing cellular wastes

Adaptations from parasitic mode of life

1. Epidermis is absent2. Developed adhesive organs3. Degeneration of muscular system and

nervous system.4. Digestive system has become

simplified5. Reproductive systems are

complicated6. Complexity of life cycle

Infestation:

Disinfestation:

difficult to remove it completely. care should be taken Complete removal is necessary give anema to the patient

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