- Water-based animals have plenty of available water and can dilute their nitrogenous waste easily. In this case, they produce ❌
- Those that are land based but live near water produce ❌
- Those that go long periods of time without water produce ❌

- If the animal lives in the ocean they will have to deal with high levels of salt outside their body - which would create an osmotic gradient causing water to want to rush out of the body.
- If the animal lives in fresh water they will have to deal with very low levels of solutes - which would create an osmotic gradient causing solutes to want to rush ❌ the body.

- Osmo regulators must be able to get rid of (or take up) any excess ❌. In humans, we get rid of excess salt via our ❌ and uptake more salt through ❌
- Osmo regulators also use up a considerable amount of energy maintaining the osmotic gradient via ❌ transport. If this didn't happen, water would come rushing out of the body and the organism would die quickly.

Animals in freshwater are continually faced with water moving ❌ their bodies (the water is hypotonic to their internal environment).
As such, an impermeable barrier-like fish scales ❌ water intake to permeable areas (thus reducing water gain and solute loss).
Usually have a ❌ uptake of salts through their gills in order to keep the necessary solute concentrations high inside the organism.
Freshwater organisms have a very high ❌ filtration rate and produce a large volume of of dilute urine. Due to the release of this volume of water, toxic ❌ can be safely washed from the body and no further energy is required to convert the ammonia to a less toxic form.

❌ Skin, scales, or skeleton

❌ Lower filtration rate causes less water loss. Kidneys also reabsorb a large amount of water from urine.

❌ Such as burrowing during the day and going into aestivation during drought (less heat, less water loss).

❌ Produced in Cellular Respiration: Water is released in cellular respiration more from fat than carbohydrates. Some animals store fat to produce more water this way.

❌ In the camel, for example, the fat stored in the hump allows a high level of production of metabolic water. The camel can survive long periods without water because its tissues can withstand higher levels of dehydration than other animals.

❌ ADH will then travel via the blood to the ❌ where it will stimulate the distil proximal tubes and collecting ducts of the nephron to become ❌ permeable to water. The result of which is more water being absorbed from the urine and being kept in the body.

❌ In this way, a hormone, ❌ controls the water balance in a mammal.

❌ Retaining this water helps to ❌ the balance of water within the organism. After which, the receptor cells in the hypothalamus will slow (or switch off) ADH production in the ❌.

❌ When an animal has lost a lot of water, the amount of intercellular and extracellular fluid ❌. This also causes the animal to have low blood pressure. This drop in blood pressure is detected by cells in the hypothalamus which causes the pituitary gland to release ADH.