Compare and contrast osmotic challenges faced by animals in freshwater, marine, and terrestrial environments, and the adaptations used to address them.

Explanation:

FRESH WATER OSMOREGULATION

The salt concentration in salt water fish is higher than the concentration found in its environment (fresh water). This causes water to enter into the body of the fish through osmosis and without regulating processes, the fish is bound to swell and likely burst.To compensate for this challenge, the kidney in fresh water fish produces a large amount of urine, causing them to lose salt. To ensure too salt is not lost beyond the basic requirement, chloride cells in the gills take up ions from the water which are transported into the blood.

MARINE OSMOREGULATION

In marine fishes, the challenge opposes that of fresh water fishes since salt content in this case is lower in their blood than in their environment. To address this challenge, marine fishes lose water constantly while retaining salts to lead to a build up. The water lost, is then made up for and replenished by continual drinking of seawater. The chloride cells in marine fishes works in a manner opposing that of fresh water fish, functioning to compliment the excretion of salts by the kidney.

TERRESTRIAL OSMOREGULATION

The major challenge of osmoregulation in  terrestrial organisms is water regulation in the body owing to their contact with the atmosphere.

Terrestrial organisms possess effective kidneys which enable osmoregulation. A series of processes including filtration, re-absorption and tubular secretion, enable regulation of fluids and water conservation.

Water passes out of the descending limb of the loop of Henle, leaving a more concentrated filtrate inside. Salt diffuses out from the lower, thin part of the ascending limb. In the upper, thick part of the ascending limb, salt is then actively transported into the interstitial fluid. The amount of salt in the interstitial fluid, determines how much water moves out of the descending limb i.e the saltier it gets, the more water moves out of the descending limb. This process leaves a concentrated filtrate inside, so more salt passes out. Water from the collecting ducts moves out by osmosis into this hypertonic interstitial fluid and is carried away by capillaries, achieving osmoregulation.

Challenges to

Aquatic Animals -

Fresh Water - Fresh water organisms live in hypotonic medium.

Marine Water - The marine organisms live in a hypertonic environment.

Terrestrial - Organisms which live on land have a common challenge of regulating water in the body due to their contact with the atmosphere.

Explanations:

In order to answer the question of comparing of osmotic challenges & adaptation of Aquatic & Terrestrial animals in their environment  

Comparing & Contrasting Challenges of Animals in -

Aquatic Animals ( Marine & Fresh water Environments)

Fresh water organisms live in hypotonic medium. This depicts that these organisms have a lower water potential than the surrounding environment. As a result, there a constant tendency for water to enter the cells by osmosis through the cell surface membrane which poses a constant threat of organisms becoming water logged.

The marine organisms live in a hypertonic environment, meaning that their inner water content is higher than the surrounding environment, hence they lose water by osmosis and then they gain salts from the seawater they drink by diffusion.

Terreestrial Animals Challenges _

Organisms which live on land have a common challenge of regulating water in the body due to their contact with the atmosphere.

The adaptations used to address them:

Aquatic Animals:

Freshwater:  Organisms which live in fresh water are able to regulate the concentration of water and salts in their bodies through the pattern of gaining water and losing salts. Fresh water organisms such as fishes undertake Osmoregulation through the release of excess water through the gills and through the excreting of large amounts of dilute urine.

Marine:

Another pattern of Osmoregulation in aquatic organisms occurs in marine species which involves the losing of water and gaining of salts to maintain a favourable and constant internal environment as exhibited by marine cartilaginous fishes i.e. sharks and rays .

For Terrestrial Animals

Terrestrial animals such as insects contain almost impermeable waxy layer which covers their exoskeletons to reduce loss of water from the body surface.

Moreover, Other terrestrial organisms i.e. invertebrates such as flateworms consists of nephridial organs with branching tubes called nephridiopores excess fluid leaves the body thereby osmoregulating the internal fluid content, and also protonephridia composed of tubes with flame cells. They also have complex nephridial organs known as metanephridia whose end opens into a coelom and the fluid from the coelom passes into the tubule bringing with it whatever it contains i.e. glucose, salts or even wastes. As the fluid moves through the tubule, needed substances like water and glucose are removed from the fluid by tubules are reabsorbed back in blood capillaries, hence carrying out Osmoregulation.

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