Question

Which of the following sets of animals produce the same substances as their chief excretory product? (a) Fish, pigeon and frog (b) Camel, housefly and snake (c) Frog, monkey and dog (d) Amoeba, ant and antelope

Short answer

The set of animals which all have the same chief excretory product is (c) Frog, monkey, and dog. They all excrete urea.

Step-by-step solution

Recognize Each Animal's Excretory Product

Start by gathering information about the excretory products of each animal. Fish excrete ammonia. Pigeons and snakes are birds and reptiles respectively, known to excrete uric acid. The frog, being amphibian, excrete urea. Similarly, Camel and antelope, being mammals excrete urea, while housefly and ants, being insects, excrete uric acid. Amoebas, being protozoans, excrete ammonia. Monkeys and dogs, all being mammals, excrete urea.

Identify Sets with Same Excretory Product

Next, compare the excretory product of each animal in the provided sets, looking for a set where all animals excrete the same substance. In option (a), fish excrete ammonia while pigeon and frog excrete uric acid and urea respectively. Thus, they do not have the same excretory product. Similarly, in option (b), camel excretes urea while housefly and snake excrete uric acid. Hence, they do not match. For option (c), frog, monkey and dog all excrete urea, so they have the same chief excretory product. Finally, In option (d), amoeba excretes ammonia while ant and antelope excrete uric acid and urea respectively. Consequently, they also do not have the same chief excretory product.

Confirm the Answer

Finally, confirm that (c) Frog, monkey and dog is the correct answer because they all excrete urea. All other options have a mix of animals excreting different products.

Key concepts

Ammonia Excretion

Ammonia is a nitrogenous waste that is highly toxic to cells. In animals, efficient removal of this waste is crucial for survival. Aquatic organisms, like fish and some amphibians, excrete ammonia directly into the water through their gills. This process, called ammonotelism, is possible because ammonia is water-soluble and can easily disperse in aqueous environments. However, the high water toxicity of ammonia means that it can only be accumulated at very low concentrations, which necessitates a constant water flow for its removal.

In the context of the given exercise, fishes were noted for excreting ammonia as their chief excretory product. This is because their aquatic habitat provides abundant water to dilute and remove the ammonia, helping to avoid ammonia's toxicity to the organism itself.

Uric Acid Excretion

Uric acid is another form of nitrogenous waste, typically found in organisms that must conserve water, such as birds, reptiles, and many terrestrial arthropods like insects. This excretion method is called uricotelism. Uric acid has a low solubility in water, which is advantageous in arid environments because it can be excreted as a paste or powder, conserving vital water in the organism. Compared to ammonia, uric acid is less toxic and can be stored in the body at higher concentrations before being eliminated, which is beneficial for animals that do not have immediate access to water.

In the textbook exercise, pigeons, houseflies, and snakes are examples of animals that excrete uric acid. This allows them to survive in environments where water is not plentiful.

Urea Excretion

Urea is the main nitrogenous waste in mammals and some amphibians, and this method of excretion is called ureotelism. Urea formation is a more energy-intensive process than that of ammonia or uric acid, but it has the advantage of being less toxic and requiring less water for excretion compared to ammonia. It is produced in the liver via the urea cycle and is excreted through the kidneys and urine. Because urea can be concentrated, it minimizes water loss, which is especially crucial for terrestrial animals that do not have constant access to water.

In the given exercise, frogs, monkeys, dogs, camels, and antelopes are classified as urea excretors. Notably, the frog is a particularly interesting case as it excretes urea while living on land and ammonia while in water, demonstrating the organism's adaptability to different environments.