Question

What is common between bat, whale, and rat?
A. Absence of neck
B. The muscular diaphragm between the thorax
C. Testes, outside the abdominal cavity
D. External ear pinna

Answer 1

Bat, whale, and rat, are all mammals. Mammals belong to the phylum Chordata. Moreover, the distinguishing feature of mammals is the presence of a muscular flap that separates the abdominal and the thoracic cavities.

Complete answer: Let us analyze all the enlisted options one by one to figure out the correct answer.
-Absence of neck: All mammals have seven neck bones. And the neck bones are present in the neck. Thus, all of these animals have a neck. In the case of the whale, the seven neck bones fuse to form the one. The necks of whales are stiff to keep them in one place while swimming. While the neck of the land-dwelling animals is loose so that they can easily check out their environment.
-The muscular diaphragm between thorax: The characteristic feature of mammals is the presence of the muscular flap that separates the abdominal and the thoracic cavities. This is known as the diaphragm. It also plays an important role during respiration.
-Testes, outside the abdominal cavity: Mammals can have intra abdominal and extra-abdominal, both kinds of testes. The testes that are present outside the abdominal cavity in a sac called the scrotum are the extra-abdominal testes. The testes within the abdominal cavity are intraabdominal. The rat has extra-abdominal tests. Bats, and Whales both have intra abdominal testes.
-External ear pinna: Almost all mammals have external ear pinna leaving a few exceptions. One such exception is the whale. It does not possess an external ear pinna. It is an aquatic adaptation. Bats and rats have external ear pinnae around their ears.
Thus, based on the above information, the similarity between Bat, Whale, and Rat is the presence of a muscular diaphragm between thorax.
Hence, the correct answer is option (B).

Note: The diaphragm plays a very important role during the process of respiration. It helps in the processes of inspiration and expiration. The diaphragm contracts to decrease the pressure on the lungs to inhale air. It relaxes to increase the pressure on the lungs to inhale out air. This is an involuntary process.