Active transport occurs in the secretion of substances into the nephron, the active transport of nutrients back into the and the selective reabsorption of salts required by the body. explain how the processes of filtration and reabsorption in the mammalian nephron regulate body composition Main Function: the kidneys of mammals regulate the internal water and salt concentrations in the body and excrete urea, the nitrogenous waste produced by mammals. Deamination: Proteins are made up of amino acids. They are made used and broken down by cell metabolism. However the body cannot store excess amino acids so any excess becomes nitrogenous waste to be removed. Deamination: This is the process by which excess amino acids are broken down in the liver. This process involves removing the part containing nitrogen (the amino group, -NH ) to form urea. The remainder is converted to carbohydrate which may be stored (as glycogen) or used immediately. Urea is transported by the blood to the kidneys and excreted as urine. The kidneys make It is an organ of filtration, reabsorption and secretion. Kidney Structure The kidneys are a pair of bean shaped organs found on either side of the abdomen. Kidneys produce urine. The main components of the mammalian urinary system can be seen in diagram 3 below. It is composed of two kidneys, two ureters, a bladder and the urethra. leaves the kidneys via the ureters and is stored in a muscular bag, the bladder. The bladder expands as it fills with urine. At a certain this expansion stimulated nerve endings in the bladder which send a message to the brain. The brain sends a message to the sphincter muscles surrounding the base of the bladder which relaxes so urine can pass through the urethra out of the body.
describe adaptations of a range of terrestrial Australian plants that assist in minimising water loss use available evidence to explain the relationship between the conservation of water and the production and excretion of concentrated nitrogenous wastes in a range of Australian insects and terrestrial mammals Aquatic Animals and Fish: These organisms directly release ammonia into the environment. This uses a lot of water, but they have no need to conserve it. Ammonia is very water soluble and is excreted through the gills. Terrestrial Animals: Releasing ammonia would be unfeasible due to lack of water. Instead, land-dwellers change ammonia into less toxic forms and release it periodically. Mammals change it into UREA and release it as urine. Birds: Birds change ammonia into URIC ACID, a whitish paste which uses hardly any water. This is lighter than using urea, and helps in flight. process and analyse information from secondary sources and use available evidence to discuss processes used by different plants for salt regulation in saline environments Maintaining Salt Concentrations in Plants Most plants cannot tolerate high salt concentrations in the root zone as it leads to water stress. The salt accumulates in its leaves and is toxic. Enzymes are inhibited by Na+ ions. Halophytes are plants adapted to living in environments. They are able to tolerate higher levels of salt than any other plants or they have special mechanisms to control their levels of salt. Three different mechanisms are salt exclusion, salt excretion and salt accumulation. Salt excluders – prevent the entry of salt into their root systems by filtration. This is a passive process that does not use energy and relies on the transpiration stream. It can be very successful. Example: The grey mangrove Avicenna marina can exclude 95% of their salt via the filtration system in its roots and lower stems. Other mangroves that rely on this system are the red mangrove Rhizophora stylosa and the orange mangrove Bruguiera gymnorrhiza. red mangrove Rhizophora stylosa