Osmoregulation Field Assignment
Osmoregulation is the process in which an organism balances the uptake and loss of water and solutes, on a cellular level, in an attempt to maintain homeostasis (Campbell and Reece, 2009). In osmoregulation, the regulation of osmotic pressure is the way in which organisms prevent their fluid from becoming to concentrated or diluted. The osmotic pressure, generated by the net movement of water across a selectively permeable membrane, driven by differences in solute concentrations on each side of the membrane, is critical in the maintenance of homeostasis. During osmosis, water flows from the solution with the lower concentration of solute to the higher concentration of solute. If the solution outside the cell has a higher solute concentration than inside the cell, it is a hypertonic solution and water will leave the cell. A hypotonic solution occurs when the cell has a higher solute concentration than out side the cell, and water will enter the cell. If the concentrations on both sides of the membrane are equal to each other, then the solution is known to be isotonic which results in no net flow of water.
Throughout evolution, many species have derived different mechanisms to deal with the ever-present problem of maintaining homeostasis of water and solutes in their given environment. The osmoregulatory strategies of freshwater and saltwater fish provide an example in which similar species are able to adapt to their environment and maintain homeostasis. Although freshwater and saltwater fish are similar in morphology, they nonetheless have vastly different types of osmoregulation as freshwater fish have to adapt to prevent excess dilution of fluid and saltwater fish must conserve as much water as possible to avoid dehydration.
The high solute concentration of seawater presents the risk for dehydration for many marine animals. Therefore, the success of saltwater fish relies in their ability to conserve water while eliminating excess salts. Most fish that live in saltwater are osmoconformers in which they alter their physiology to be isotonic to the environment. Because these fish constantly lose water from osmosis, they balance osmotic pressure by consuming vast amounts of seawater and expelling the salt ions from their gills and kidneys (Campbell and Reece, 2009). In the gills, marine fish have specialized cells that actively transport sodium chlorides out of the cell, resulting in the passive transport of sodium ions to follow. The kidneys excrete excess magnesium, calcium and sulfate ions that only permit the loss of small amounts of water. These features allow marine fish to conserve the maximum water possible (Campbell and Reece, 2009).
Chondrichthyes have unique...