Fishes that have swim bladders can regulate their density and, thus, their buoyancy. There are two types of swim bladder: physostomus and physoclistus. The ancestral version is the physostomus version, in which the swim bladder is connected to the esophagus via a short tube (see the figure above). The fish fills this version by swimming to the surface, taking gulps of air, and directing them into the swim bladder. Air is removed from this version by "belching." The physoclistus version is more derived, and has lost its connection to the esophagus. Instead, gas enters and leaves the swim bladder via special circulatory mechanisms within the wall of the swim bladder.
-The presence of a swim bladder allows the typical ray-finned fish to stop swimming and still
A)effectively circulate its blood.
B)be highly manoeuvrable.
C)use its lateral line system.
D)use its swim bladder as a respiratory organ.
E)not sink.

Question

Fishes that have swim bladders can regulate their density and, thus, their buoyancy. There are two types of swim bladder: physostomus and physoclistus. The ancestral version is the physostomus version, in which the swim bladder is connected to the esophagus via a short tube (see the figure above). The fish fills this version by swimming to the surface, taking gulps of air, and directing them into the swim bladder. Air is removed from this version by "belching." The physoclistus version is more derived, and has lost its connection to the esophagus. Instead, gas enters and leaves the swim bladder via special circulatory mechanisms within the wall of the swim bladder.
-The presence of a swim bladder allows the typical ray-finned fish to stop swimming and still
A)effectively circulate its blood. 
B)be highly manoeuvrable. 
C)use its lateral line system. 
D)use its swim bladder as a respiratory organ. 
E)not sink.

Quizplus · Accepted Answer

The swim bladder allows the fish to regulate its density and buoyancy, preventing it from sinking.

Fishes That Have Swim Bladders Can Regulate Their Density And