11th Class Biology Excretory Products and their Elimination Excretory Organs Of Different Organism

(1) Protozoans : In protozoans like Amoeba and Paramecium carbon dioxide and ammonia are mostly excreted out by diffusion through general body surface. It is considered that the contractile vacuoles also play some role in the removal of excretory products.  

(2) Sponges : In sponges, the nitrogenous metabolic waste (ammonia) leaves the body in the outgoing water current by diffusion.

Most of the sponges are marine and have no problem of surplus water in their cells. A few sponges lie in hypotonic fresh water and have contractile vacuoles in most of their cells.

(3) Coelenterates : Hydra also lacks special excretory organs. The nitrogenous waste products like ammonia are removed through the general surface of the body by diffusion. Some nitrogenous waste products are also thrown along with indigestible matter through the mouth.  

(4) Platyhelminthes : Planaria, liverfluke and tapeworm possess a large number of excretory cells called the flame cells (solenocytes) or protonephridia and long excretory ducts (also called canals of vessels). The flame cells open into the ductules which in turn open into the excretory duct.

(5) Nematoda : The round worms such as Ascaris have H-shaped excretory system. It is made up of a single Renette cell. in entire length of body. It consists of two longitudinal excretory canals connected anteriorly by a network of transverse canals. A short terminal duct opens outside via excretory pore. Ascaris is excretes both ammonia and urea.

(6) Annelids (Earthworm) : In earthworm excretory system also known as nephridial system, which consist of 3 types of nephridia Pharyngeal, septal, and integumentary nephridia. All nephridia commonly called micronephridia. Earthworm excrete 40% urea, 20% ammonia, 40% amino acids. Earthworm mainly ureotelic. Chloragogen cells found in coelomic fluid also excretory in nature. Blood gland in earthworm found in 4, 5, 6 segment, serves for excretion, manufacture of blood corpuscles and Hb.

(7) Arthropods : The excretory system of the adult Prawn (crustacean) consists of a pair of antennary or green glands, a pair of lateral ducts and a single renal sac.

Insects, centipedes, millipedes and arachnids like scorpion and spider posses Malpighian tubules as their principal excretory organs. In the Malpighian tubules bicarbonates of potassium and sodium, water and uric acid are formed. A large amount of water and bicarbonates of potassium and sodium are reabsorbed by the cells of Malpighian tubules and then transferred to the blood (haemolymph). Uric acid is carried to the alimentary canal of the insect and is finally passed out through anus. Spiders and scorpions possess Malpighian tubules and coxal glands both for excretion.  

(8) Molluscs : They have one or two pairs of kidneys or organs of bojanus and keber's organ for excretion in unio. 

(9) Echinoderms : Specialized excretory organs are absent in echinoderms (e.g., Starfish). The excretory products, chiefly ammonia, urea, and creatinine are eliminated by diffusion through dermal branchiae (primitive gills) and tube feet. Amoeboid coelomocytes also excretory.

Excretory organs of different organisms