Question

Excretion of nitrogenous waste product mainly as uric acid by birds is helpful in (a) Conserving body heat (b) Conserving water (c) Eliminating excess water (d) Eliminating excess body heat

Short answer

The answer is (b) Conserving water. The excretion of nitrogenous waste as uric acid by birds helps them to conserve water.

Step-by-step solution

Understand the Excretion Process in Birds

Birds excrete their nitrogenous wastes as uric acid in the form of a semi-solid paste instead of urea or ammonia. This is because uric acid is much less toxic than urea or ammonia. Therefore, it does not need to be stored in water and can be lost with minimal water loss.

Identify the Advantages of Uric Acid Excretion

The main biological benefit of excreting nitrogenous wastes as uric acid is that it is less costly in terms of water lost. Because uric acid is not water soluble, it can be excreted with very little water. This is particularly beneficial for birds as it minimizes their need for water.

Answer the Multiple Choice Question

Given this information about uric acid and its excretion, the most relevant answer out of the four options provided in the question is (b) Conserving water, as excreting uric acid helps to minimize water loss in birds.

Key concepts

Uric Acid

Birds excrete nitrogenous waste primarily as uric acid. This is quite different from many mammals, which excrete waste in the form of urea. Uric acid has a major characteristic that makes it beneficial for birds: it is not very soluble in water. This means it can be excreted as a paste with very little moisture.
This semi-solid form is crucial for birds because they cannot afford to lose a lot of water, especially those living in dry environments. By converting waste into uric acid, birds can conserve water effectively, which is vital for their survival in various habitats.
Additionally, since uric acid is less toxic than other nitrogenous waste products like urea or ammonia, it does not require diluting in large volumes of water to be stored safely in the body. This makes uric acid a much more efficient waste product for birds.

Nitrogenous Waste

Nitrogenous waste is a byproduct of the metabolism of proteins and nucleic acids. In many animals, these wastes are excreted mainly in the form of ammonia, urea, or uric acid. Among these, uric acid is the least toxic.
This low toxicity level allows birds to store the waste without needing to dilute it, unlike ammonia which needs to be excreted quickly and in a diluted solution due to its toxicity. Birds have adapted to excrete uric acid to suit their physiology and environmental needs, a process which enables them to maintain a balance in their internal water content.
Therefore, the way birds convert nitrogenous waste plays a significant role not only in managing toxicity but also in their hydration strategy.

Water Conservation

One of the key benefits of birds excreting uric acid is water conservation. Birds need to manage their water levels carefully. Many birds live in environments where water is scarce, like arid regions or during long flights over oceans.
By excreting uric acid, birds reduce their water loss significantly. Uric acid's semi-solid form helps in minimizing the volume of water required for excretion. This adaptation is essential for birds to thrive in environments where access to water is limited.
As such, the physiological mechanism of using uric acid helps birds conserve water, allowing them to survive and maintain their hydration status.

Bird Physiology

Bird physiology is uniquely adapted to manage nitrogenous waste and water levels efficiently. Birds possess kidneys that are structured to concentrate uric acid into a paste-like consistency, enabling them to excrete it with minimal water loss.
This adaptation is crucial to a bird's survival, as efficient water management is necessary for maintaining metabolic processes and overall health. Furthermore, the ability to conserve water by excreting uric acid allows birds the flexibility to inhabit a wide range of environments, from lush forests to dry deserts.
Understanding bird physiology, especially their excretory adaptations, reveals the intricate ways in which birds cope with the challenges of their diverse habitats and ecological niches.