AP BIOLOGY

Detailed explanation-1: -Birds excrete nitrogenous wastes as uric acid in the form of pellet or paste with minimum loss of water and are called uricotelic animals.

Detailed explanation-2: -Birds produce uric acid – which is white and insoluble, rather than the soluble urea we excrete – as a water-saving measure to keep body weight lower. The faecal matter is the dark part of the dropping.

Detailed explanation-3: -Birds, unlike mammals, do not have separate exits for urine and feces. Both waste products are eliminated simultaneously through the cloaca. While mammals excrete nitrogenous wastes mostly in the form of urea, birds convert it to uric acid or guanine, which reduces water loss in comparison.

Detailed explanation-4: -Nitrogenous Waste in Birds and Reptiles: Uric Acid It is water insoluble and tends to form a white paste or powder; it is excreted by birds, insects, and reptiles. Conversion of ammonia to uric acid requires more energy and is much more complex than conversion of ammonia to urea Figure 22.13.

Detailed explanation-5: -Uric acid is excreted by the animals which conserve water, at least during parts of their life cycle, such as birds, terrestrial reptiles, insects and some snails. In this case ammonia is converted into uric acid because it is less toxic than ammonia but it is insoluble in water.