excretion and homeostasis system questions and answers

 

Q:    Describe excretion in Hydra?

 

Ans:  EXCRETION IN HYDRA

                    Hydra has no structures specialized for excretion. Carbon dioxide and major nitrogenous waste, ammonia, leave the cells by diffusion. Almost every cell is either adjacent to the outside pond water or to the digestive cavity, so that there is a ready place to the wastes.

                     Hydra lives in freshwater therefore its cells have a lower concentration of water then does the surrounding pond. Water constantly enters the animals faster than it diffuses out. The mechanism by which the surplus water is removed is not fully known but it must require the expenditure of energy.

 

Q:   Describe excretion in Planarian?

 

Ans:   EXCRETION IN PLANARIAN

             In planarian excretion occurs by diffusion as well as by a specialized excretory system. This system has a series of branching tubes or ducts, the outer ends of which end up in flame bulbs.

 

FLAME CELLS

               Each flame cell has the cytoplasmic prolongations. The cytoplasm is hollowed out to form a large cavity which is continuous with that of the finer tubes. Due to this cavity the nucleus is displaced. A bunch of flagella hangs down into the cell. Due to the movement of these flagella, flame cells appear like flickering flame of a candle, so it is called flame cell. Flame cells absorb waste materials such as carbon dioxide, salts and ammonia from its surrounding tissues. The flagella keep the fluid circulating in the tubules. It is also thought that the flagella cause a sufficient suction pressure o draw the fluid into the lumen of the flame cell from the surrounding parenchyma. Due to the action of the body through excretory pores. The excretory system also acts as osmoregulatory in function and removes excess water.