Question

The lungs of early bony fishes evolved into swim bladders. This change hides the primary effect of
A) Improving feeding efficiency
B) Supplementing gill respiration
C) Aiding reproduction
D) Providing buoyancy

Answer 1

Hint: In some early bony fishes swim blades or air bladders were developed. This provides buoyancy to fish in water. This swim bladder is filled with gas and prevents fishes from drowning. These fishes were called Dipnoi.

Complete answer:
Some bony fishes which have air bladders or swim bladders are called dipnoi. These were early bony fishes included in subclass sarcopterygii.
Development of the air bladder is considered beneficial for fishes because these were able to maintain its depth in water without floating upward or sinking.
Swim bladder also helps in respiration, sound production, perception of pressure fluctuation.
This organ allows fish to regulate their flooding, and maintains the present water level, without wasting resources in swimming. This organ helps fish control their flourish. The swimming bladder develops according to the lungs. In several bony fish swimming bladders are found, but not in cartilage fish.

So, the correct answer is option D) Providing buoyancy

Note:
Dipnoi fishes are also known as lung fishes. Examples are Protopterus, Lepidosiren, Neoceratodus, etc. The swimming bladder emerges in the intestine from its dorsal wall and typically gets blood supplies from the dorsal aorta while the lung's vertebrate originates from its ventric wall.
In nearly all osseous fishes, the swimming bladder normally acts as a hydrostatic organ. The swimming bloat in fish leads the entire party through an evo-lutionary channel beginning from a very negligible cellular extension.