Question

The animal that mostly depends on ‘Metabolic water’ to survive for long periods without drinking water
A. Didelphis
B. Ornythorhynehus
C. Macropus
D. Dipodomys

Answer 1

Hint: Water is an essential requirement for all the organisms to survive. In certain cases such as extreme environmental conditions where there is water scarcity, the animals adapt to the conditions by conserving water in the body. Animals also save water through the changes in their diets and metabolic changes.

Complete answer:
The water created by the metabolic activities in a living organism is known as metabolic water. The water is produced through the oxidizing energy containing substances in the food material of the organism. The different constituents of food are fat, protein and carbohydrates and these constituents upon metabolism produce water which is known as metabolic water. The organisms that are exposed to extreme habitats such as xerophytic habitats and scanty water, are dependent on the availability of the metabolic water produced from their diet.
Didelphis is the koala that is found in the Australian continent. They inhabit the eucalyptus trees and depend on the tree leaves for food. The animal depends upon the metabolic water that is formed during the digestion of the leaves. The water requirement is achieved by the water produced through metabolism. They pass off extremely dry pellets like fecal matter and thereby conserving water.
Ornithorhynchus is commonly known as the duck billed platypus. It is semiaquatic in habitat and is an egg laying animal. It belongs to the monotremes which is the only mammal that lays eggs rather than giving birth to young ones. It inhabits small streams and rivers of eastern Australia.
Macropus is the marsupial genus which contains the kangaroos and are found in Australia. Kangaroos have a strict herbivores diet and need very little water to survive.
The genus Dipodomys includes the kangaroo rats which are small, nocturnal rodents that survive in hot, arid and semi-arid conditions. They are sensitive to temperature changes and reduce loss of water by reducing metabolic rate. The rate of evaporation is also very much reduced.

Hence, the correct answer is option (A).

Note: Metabolic water is the water formed by the metabolic processes occurring during the digestion of food. The water produced is conserved by minimal loss through evaporation and excretion. Koala or Didelphis is an animal that depends on the metabolic water for water requirements and surviving long periods in absence of water.