EXCRETION Do Now - Give as many examples of EXCRETION as you can. And it’s not this The metabolic activities of living cells produce waste materials. EXCRETION – is the life process by which the wastes of metabolism are removed from the body. The metabolic wastes that are removed are WATER CARBON DIOXIDE MINERAL SALTS NITROGENOUS WASTES (OXYGEN) Food Waste can be converted into AMMONIA Ammonia is a toxic substance. NH3 Ammonia must be washed out of and away from organisms immediately so they aren’t poisoned. Organisms that live in a watery environment can excrete ammonia directly into the environment by diffusion. Fresh water Paramecium's can excrete a large amount of water using their CONTRACTILE VACUOLES. In humans and other mammals, ammonia is converted into UREA by the liver. It is moderately toxic. Urea is soluble in water, and can be eliminated in urine and sweat. Some organisms convert ammonia to URIC ACID. It takes a lot of energy to produce uric acid, but there’s a big payoff. URIC ACID can be excreted as a dry waste. This helps organisms like birds conserve water. Looking like bird poop can be good! caterpillar fungus moth Other waste products of plant metabolism can be stored in the plant cell VACUOLES. All the cells of the hydra are in contact with the water. Excretion takes place by diffusion through the cell membranes. Freshwater hydras excrete CO2 and the nitrogenous waste product ammonia. In the earthworm, carbon dioxide is excreted by diffusion through the thin, moist skin. CO2 Water, mineral salts, and urea are excreted by pairs of excretory organs called NEPHRIDIA. Wastes are filtered out of the body fluid by the nephridia and excreted through pores into the environment. NEPHRIDIA are found in most of an earthworm’s body segments. In the GRASSHOPPER, carbon dioxide from the body cells diffuses into the tracheal tubes. It leaves the body through the SPIRACLES. Water, salts, and uric acid crystals accumulate in the MALPIGHIAN TUBULES, which are the excretory organs. From the MALPIGHIAN TUBULES, the wastes pass into the digestive tube, where most of the water is reabsorbed. The metabolic wastes of humans include carbon dioxide, water, salts, and urea. Excretory wastes pass from the cells into the blood, and are carried to the excretory organs that expel them from the body. Brain Pop The human excretory organs include the LUNGS LIVER KIDNEYS and SWEAT GLANDS In humans, carbon dioxide and water vapor are excreted by the LUNGS when we exhale. This is what happens to your lungs when you smoke. The LIVER is a large organ that performs many functions essential to human survival. The liver is also responsible for the breakdown of red blood cells. This is what happens to your liver when you abuse alcohol. Water, salts, and UREA are excreted by the URINARY SYSTEM. Human KIDNEYS remove urea from the blood and regulate water and salts in the blood. As water is reabsorbed by the kidney, URINE is formed. The urine passes through the URETERS to the URINARY BLADDER where it is stored. Urine is eliminated from the body through the URETHRA. People who suffer kidney failure undergo DIALYSIS which filters the blood through a machine to remove the wastes. Can you drink your own urine to stay alive? click here Medicine from URINE?? click here The SWEAT GLANDS excrete wastes including water, salts, and a small amount of urea. The mixture of wastes and water excreted by the sweat glands is called sweat, or PERSPIRATION. PERSPIRATION functions primarily in the regulation of body temperature. As sweat evaporates from the skin, heat is absorbed from skin cells. The absorption of heat lowers body temperature. Temperature regulation is an example of homeostasis. The normal human body temperature is 98.6◦F. When your body temperature is out of balance, it is a sign of illness.