Parasitic Helminthes flat worms in order to lead parasitic life they will show a number of morphological and physiological adaptations.

I Morphological Adaptations:

In order to lead parasitic life many morphological adaptations are developed site

1) Loss of organs

2) Formation of New organs

3) Modification of existing organs.

Loss of organs : Sense organs and locomotory organs are necessary for free moving organisms but they are not useful for parasites. Hence they are lost.

1. Loss of Sense organs: The endoparasites have no sense organs.

2. Loss of Locomotory organs: The endoparasites have no locomot­ory organs. But the larval forms of some parasites may retain locomotory organs,

a) In the  life history of Fasciola hepatica-Miracidium larva   will show ciliated epidermis. So that they swim in water in search of a snail,

b) Tape worms have no locomotory organs throughout their life.

3. Loss of digestive system: Tape worms lead endoparasitic life in the body of human beings or vertebrate hosts. Their large, long flat body provides good surface area to absorb organic food from the host hence there is no need for digestive system. In all tape worms digestive system is absent.

4. Formation of New organs: In order to lead parasitic life the organisms require additional structures.

1. Development of adhesive organs : in order to attach to the host body suckers in flukes, hooks and suckers in tape worms are developed

2. Cuticle: These parasites develop thick resistant cuticle to get protec­tion from the digestive enzymes and antitoxins produced by the host.

3. Modification of existing organs : h order to lead parasitic life the existing structures are modified.

1. Flat body : The body becomes fiat and thin hence it can fit in narrow spaces of the host, it can absorb organic food and it can diffuse Co2 from its body at a faster rate.

2. Shell around eggs: The fertilized egg is covered by thick resistant shell, which will protect the embryo from desiccation, high temperature .

II. Physiological adaptations: The parasites will show certain physi­ological adaptations to lead parasitic life they are

1. Anaerobic respiration: The endoparasites like tapeworms will perform anaerobic respiration.

2. Antienzymes: The tape worms living in the intestine of the host will secrete antienzymes so that they can neutralize the enzymes of the host. Thus they can live in the intestine of host.

3. Excessive reproductive Potential: The parasites in order to continue their race during migration from one host to another will produce thousands of shelled eggs. At least few of them will reach the host and complete their life cycle.

They also show complex life cycle with many larval stages. At each and every stage the number will multiply so that the chance of continuation of the race is increased.

Thus parasitic flat worms will show parasitic adaptations.