The stream-lined shape of fishes is an adaptation for

Step 1: Analyze the question The question asks about the function of the stream-lined (tapered, torpedo-like) body shape in fishes.

Step 2: Explain the concept A stream-lined body is narrow at both ends and widest in the middle. This shape reduces drag (resistance) as the fish moves through water. Water is much denser than air, so moving through it takes a lot of energy. A smooth, tapered body lets water flow over it with minimal turbulence.

Step 3: Evaluate the options

• A. Securing mates: Mating depends on courtship behaviour, colour, and chemical signals, not body shape.
• B. Easy movement: Correct. Reduced water resistance makes swimming faster and uses less energy.
• C. Obtaining food: Feeding adaptations include mouth shape, teeth, and gill rakers. Body shape only helps indirectly.
• D. Defence and attack: Defence adaptations include spines, camouflage, and scales. Streamlining helps escape only indirectly, and the main function is still movement.

Step 4: Answer The stream-lined shape is primarily an adaptation for easy movement through water.

Tip: In Biology, link the structure to its direct function. "Stream-lined" means less resistance, which means easy movement. Think of the same idea in aeroplanes, boats, and birds. Other fish adaptations to remember are fins (balance and steering), the swim bladder (buoyancy), and gills (breathing).