2. EXCRETORY SYSTEMS Excretion is the process by which metabolic wastes and excess substances are removed from the organism. The process of excretion also removes excess heat from the body, thus helping to keep the temperature of the body constant. In humans and other complex animals, the organs of excretion are; lungs skin kidney liver These organs work together with the circulatory, nervous and endocrine systems to keep the body’s internal environment constant. (homeostasis) @

3. Major Metabolic Wastes CO 2 is formed during cellular respiration Water is formed during cellular respiration and dehydration sysnthesis Nitrogen compounds - Ammonia NH 3 - Urea [CO(NH 2 ) 2 ] - Uric acid C 5 H 4 N 4 O 3 Mineral salts Sodium chloride and potassium sulphate build up during metabolism

4. Ammonia NH 3  is produced by cells  solubility of NH 3 in water is high  it is the most poisonous nitrogen compound  excretion of NH 3 requires high amount of water  most of the aquatic animals excrete NH 3  is produced by deamination of aminoacids

5. Urea [CO(NH 2 ) 2 ]  is produced by the reaction of CO 2 and NH 3  it is less poisonous than NH 3  excretion of urea requires less water than NH 3  solubility of urea in water is less than NH 3  it is the excretory material of amphibian and mammals

6. Uric Acid C 5 H 4 N 4 O 3  is synthesized from the products of ammonia metabolism  can be crystalized  is not dissolved in water  is the least poisonous  removal of uric acid requires less water than the removal of urea and NH 3  terrestrial insects, reptiles, and birds excrete uric acid

7. EXCRETION IN PROTISTS  Metabolic wastes are CO 2, mineral salts and ammonia. They are diffused out of the cell through the cell membrane into the surrounding medium.  Freshwater protist (ameba and paramecium) pumps out excess water with their contractile vacuole by active transport.

8. EXCRETION IN HYDRA  Metabolic wastes (CO 2, mineral salts, ammonia) are diffused out of the cell through the cell membrane to the surrounding medium.

9. EXCRETION IN PLANARIAN

10.  A series of tubules that run the length of the body make up the excretory system of the planaria. Side branches of the tubules have cells called flame cells.  These cells remove excess water and liquid wastes from the body and pass them into ducts. The contents of the ducts pass out of the worm through small excretory pores on the dorsal surface.  CO 2 and NH 3 are excreted from cell surface to the surrounding medium by diffusion. flame cells excretory pore

11.  CO 2 and NH 3 are excreted from cell surface to the surrounding medium by diffusion.  H 2 O is excreted from protonephridium to the surrounding medium (osmoregulation). Protonephridium = flame cells + excretory + excretory tubes pore  Flame cells receive H 2 O from the body spaces and by beating of cilia on their structure force H 2 O to move into the excretory tubes. H 2 O is then excreted from excretory pores (nephridiopore).  A little amount of CO 2 and NH 3 excreted with H 2 O.

12. EXCRETION IN EARTHWORMS  In earthworm most of the cells are not in contact with the surrounding environment, so they need special excretory organs to remove the metabolic wastes.  The excretory organs of the earthworm are nephridia. These structures are found in pairs in most segments of the earthworm’s body. They excrete dilute urine.  Urine includes water, mineral salts, ammonia and urea.

13. EXCRETION IN EARTHWORMS

14. EXCRETION IN INSECTS

15.  The excretory organs of insects are the malpighian tubes. The slender excretory tubes are bathed directly by blood. Substances from the blood enter the tubules by diffusion and active transport.  From the tubules, these materials pass into the intestine.  Water, nutrients and other useful substances are reabsorbed from the tubules and the digestive tract. Then they are returned to the body fluids.  The dry nitrogenous waste product is uric acid, it passes out of the body with the feces through the anus.

16. EXCRETION IN BIRDS

17.  Nitrogenous wastes in the form of uric acid are removed from the blood by the kidneys.  Since there is no urinary bladder, these wastes pass through the ureters to the cloaca. They combine with the fecal matter in the cloaca to form a whitish, semisolid material.

18. OSMOREGULATION IN BONY FISH