The kidneys are made of small tubes, called tubules, providing an extensive area for exchanging solutes, water, and wastes. The main processing centers of this system in our body are our kidneys, compact organs located towards the back of the abdomen. The urinary system plays an important role in homeostasis, forming and excreting urine while regulating the amount of water and solutes in body fluids. Although an animal must expend more energy to excrete uric acid, this is balanced by great savings in body water. In most cases, uric acid is excreted as a semisolid paste (the white material we see in bird droppings is mostly uric acid). It is a relatively nontoxic nitrogenous waste that can be safely transported and stored in the body to be released periodically by the urinary system. Uric acid is a water-insoluble precipitate and so water isn’t used to dilute it. Insects, land snails, and many reptiles, including birds, convert ammonia to uric acid to avoid water loss completely. Some toads excrete ammonia as tadpoles but excrete urea as land-dwelling adults. Some animals can switch between excreting ammonia and urea depending on environmental conditions. An advantage to excreting urea is its very low toxicity. It is a soluble form of nitrogenous waste that is produced in the liver by a metabolic cycle that combines ammonia with carbon dioxide. Mammals, adult amphibians, sharks, and some bony fishes excrete urea as their major waste product. Image by CNX OpenStax is licensed under CC BY 4.0 The disadvantage though is that energy is needed for this to occur.Īnimal waste products. Since most terrestrial animals cannot afford to lose water in amounts needed to routinely excrete ammonia, they convert it into less toxic compounds that can be safely stored in the body.
Small soft-bodied invertebrates like jellyfish excrete ammonia while fishes excrete it through thin membranes on their gills.īecause it is so toxic, ammonia can be tolerated at very low concentrations and must be transported in dilute solutions. If an animal is surrounded by water, ammonia readily diffuses out of its cells and body. It is too toxic to be stored in the body, but it is very soluble and diffuses rapidly across cell membranes. Most aquatic animals dispose of their nitrogenous waste as ammonia ( NH 3). The type of waste products produced and how they are excreted depends on the animal’s evolutionary history and habitat. Metabolism produces a number of toxic by-products and through excretion, the process where animals dispose of metabolic wastes, they are eliminated. Osmoregulation creates waste and waste disposal is an important aspect of this process as most metabolic waste is dissolved in water to be removed from the body.
This control over concentrations of solutes in cells to prevent excess uptake or loss of water is known as osmoregulation. Freshwater and land-dwelling animals and many marine invertebrates are also osmoregulators. The second is to be an osmoregulator and have your internal solute concentrations independent from the outside environment. Most marine invertebrates are osmoconformers, balancing concentrations in relation to seawater. One is to be an osmoconformer and have body fluids with solute concentrations equal to their surroundings. They can maintain this balance in two ways. To survive, all animals need to maintain concentrations between water and solutes in their body within a certain range. It also regulates the chemical and water balance of the blood. The urinary system removes waste products from the blood and excretes urine.
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