Question

Uric acid is excreted by (a) Pigeon (b) Frog (c) Rabbit (d) Man

Short answer

The correct answer is (a) Pigeon.

Step-by-step solution

Understand Variations in Animal Excretion

Different animals excrete different waste products, largely determined by their metabolic activities and habitat requirements. In the context of this problem, it's necessary to understand which animals excrete uric acid.

Identify the Correct Choice

The options provided are Pigeon, Frog, Rabbit, and Man. Out of these, Pigeons are birds and are known to excrete uric acid. It is a mechanism for getting rid of nitrogenous waste and conserving water.

Confirm the Answer

By identifying the correct animal, we confirm that (a) Pigeons excrete Uric acid.

Key concepts

Uric Acid Excretion

The process of uric acid excretion is a crucial aspect of how some animals, particularly birds like pigeons, eliminate nitrogenous waste. Unlike mammals, which primarily excrete urea, birds and reptiles need an efficient method to dispose of nitrogen-containing compounds without losing too much water. Their adaptation, in evolutionary terms, has been the production and excretion of uric acid.

Uric acid is less toxic than ammonia and is excreted in a semisolid form. This significantly reduces water loss, which is especially beneficial for animals living in arid habitats or those who have limited access to water. When pigeons excrete uric acid, it's visible as a pasty white and dark mixture, quite different from the urine of mammals. Students should note that a well-hydrated human will excrete a significant amount of uric acid in urine, but this is alongside urea and is not the primary nitrogenous waste.

Nitrogenous Waste in Animals

Nitrogenous waste in animals is a byproduct of metabolizing proteins and nucleic acids. Their excretion is vital for the health of an organism. Different species have developed various waste products, such as ammonia, urea, or uric acid, based on their habitat, evolutionary history, and physiology.

Ammonia is excreted by aquatic organisms due to its high solubility and less energy-intensive production. In contrast, urea is less toxic and less soluble, suitable for mammals that have moderate access to water. Arid and terrestrial habitats have seen the emergence of uric acid excretion because it allows animals to conserve water. It is important to highlight that the form of nitrogenous waste excreted often correlates with the availability of water in the environment and the evolutionary lineage of the organism.

Metabolic Waste Products

Metabolic waste products are substances that are formed as a byproduct of the metabolic processes in living organisms. These include carbon dioxide from cellular respiration, as well as a variety of nitrogenous wastes from the breakdown of proteins and nucleic acids.

Waste removal is imperative as the accumulation of these byproducts can be toxic. Cells and systems within animals are adapted for filtering, transforming, and excreting these substances. In humans, the kidneys play a central role in filtering blood and excreting urea and uric acid, while the liver also contributes by breaking down toxins. Students studying excretion should be aware that metabolic waste also includes compounds like bile pigments and creatinine, aside from the nitrogenous wastes, illustrating the broad scope of what our body must regularly eliminate to maintain homeostasis.