Question

In aquatic organisms, the waste end product of nitrogen metabolism is (a) Urea (b) Nitrogen (c) Ammonia (d) Allantois

Short answer

The correct waste end product of nitrogen metabolism in aquatic organisms is \(\text{c) Ammonia}.\)

Step-by-step solution

Understand Metabolism

Nitrogen metabolism involves the metabolic processes by which living organisms process nitrogen compounds. In humans and some other animals, these processes convert nitrogen into waste products such as urea and uric acid, which are then excreted.

Understand Aquatic Organism Metabolism

In many aquatic organisms, including most fish, the preferred method for excreting nitrogenous waste is through ammonia, due to its very high solubility in water. These organisms can then release the waste into their environment without the bioenergetic cost of converting it into relatively safer compounds like urea or uric acid.

Identify Correct End Product

Given the understanding that aquatic organisms mostly excrete nitrogenous waste in the form of ammonia, it leads to the conclusion that the correct answer in regard to the waste end product of nitrogen metabolism in aquatic organisms is ammonia.

Key concepts

Ammonia Excretion

Aquatic organisms, especially fish, excrete ammonia directly into their surrounding water. This is because ammonia is highly soluble and can be easily disposed of without requiring a lot of energy. The process of excreting ammonia begins in the cells, where nitrogen-containing compounds like amino acids are broken down.

During this breakdown, ammonia is produced as a byproduct. Since ammonia is toxic, it must be quickly eliminated from the body. In water, ammonia diffuses rapidly due to its high solubility; thus, fish and other aquatic animals can excrete it directly into the water through their gills or skin.

In contrast to land animals that convert ammonia into less toxic substances such as urea or uric acid to conserve water, aquatic organisms take advantage of their watery habitat to dispose of ammonia efficiently. This process is known as ammonotelism and is a key aspect of the nitrogen metabolism in aquatic animals.

Nitrogenous Waste Products

The metabolism of nitrogen in living organisms results in various nitrogenous waste products. While ammonia is the primary waste form in aquatic environments, other organisms might produce urea or uric acid. The type of nitrogenous waste an organism produces is influenced by its evolutionary history and habitat.

Ammonia is the most toxic form and requires lots of water to be diluted for safe excretion. In contrast, urea is less toxic and uric acid is even less so, being almost non-toxic and insoluble in water, which makes it suitable for organisms in arid environments.

Nitrogenous wastes are the result of the breakdown of proteins and nucleic acids during metabolism. The efficient removal of these wastes is crucial for maintaining the well-being of organisms as the accumulation of these toxic wastes can impair cellular function and can even be fatal.

Aquatic Organism Metabolism

The metabolism of aquatic organisms has adapted to their environment in fascinating ways. These adaptations include the way they handle the excretion of toxic nitrogenous waste like ammonia. Because water is readily available in their environment, aquatic organisms can afford to excrete nitrogenous wastes in the most energy-efficient, albeit toxic, form — ammonia.

The process occurs mainly through diffusion, which does not require energy expenditure, thereby being a highly efficient excretion method. However, there's a balancing act involved; the surrounding water must be relatively free of ammonia to prevent toxicity and ensure the diffusion gradient allows ammonia to exit the organism.

Furthermore, the rate of ammonia excretion can be affected by several factors, including water temperature, the species of aquatic organism, and the availability of oxygen in the water, which is essential for metabolic processes. Effective nitrogen metabolism is crucial for the survival, growth, and reproduction of aquatic organisms.