Question

5. Describe the excretory (osmoregulatory) system found in the members of Phylum Platyhelminthes. Explain the structure and function of flame cells.

6. Name the four classes found in Phylum Platyhelminthes. What group of animals does each include? 7. What sense organs are found on the head of Planaria? What are their functions?

Answer 1

5.

Excretory (Osmoregulatory ) system of Phylum Platyhelminthes

Phylum Platyhelminthes or flat worms are a group of unsegmented invertebrates. Members of the Phylum Platyhelmimthes have an excretory system . This system removes excess water from the organism's body and also removes waste products.The excretory syetem is made up of network of tubules throughout the body. The excretory system have Protonephridia and Flame cells. Flame cells in flatforms which functions as a kidney in waste removal.

Flame cells

Flame cells are the excretory organs in Platyhelminthes. They are cup shaped structures. Bundles of flame cells are known as protonephridia. Flame cells have a nucleus, cilia, tube cell. The inner surface of tube cell is also covered by cilia. Cilia help in the movement of the liquid.

Function of Flame cells

* Removal of waste products

* Maintaining Ionic balance

* Osmotic pressure balance

6.

Four claases of phylum Platyhelminthes

* Turbelleria

* Monogenea

* Trematoda

* Cestoda

Turbelleria

- Freeliving, aquatic organisms

- presence of Rhabdites

- example : Planaria, Geoplana, Dugesia

Trematoda

- Mostly parasites

- Rhabdites absent.

- Unciliated body.

-Presence of suckers.

- Example : Cotylapsis, stichocotyle

Monogenea

- Seen as ectoparasites on aquatic vertebrates.

- presence of suckers.

- Presence of haptors.

- Example : Diplozoon, Polystoma

Cestoda

- seen as gut parasites in vertebrates.

- Known as tape worms.

- Example: Archegetes, Taenia, Echinococcus.

7.

Sense organs in head of Planaria and Functions

The sense organs present in the head of planaria are,

* Eyes

* Sensory lobes

Eyespots or ocelli help to detect the presence and intensity of light .It is made of simple nerve cells- ganglion. They cannot form images. Eyespots act as Photoreceptors.

Sensory lobes or auricles sensitive to touch, moisture and chemicals. They are chemoreceptors.