What term is used for the resistance experienced by a moving organism in water?

What term is used for the resistance experienced by a moving organism in water?

• A. Countershading
• B. Chordata
• C. Chitin
• D. Drag

Answer: (D)

Drag is the resistance experienced by a moving organism in water, a force that acts opposite to the direction of motion as water flows past the body. It comes mainly from viscous friction between the water and the surface (skin friction) and from pressure differences as water is redirected around the body (form drag). The size of drag depends on speed, the body's cross‑sectional area, shape and smoothness, and the water’s density and viscosity. A useful way to think about it is that drag increases with the square of speed and scales with a drag coefficient and area. Animals reduce drag through streamlined shapes and smooth surfaces to minimize both friction and form drag. The other terms describe different concepts: a camouflage pattern, a phylum, and a structural polysaccharide, none of which capture the resistive force experienced during movement through water.

Drag is the resistance experienced by a moving organism in water, a force that acts opposite to the direction of motion as water flows past the body. It comes mainly from viscous friction between the water and the surface (skin friction) and from pressure differences as water is redirected around the body (form drag). The size of drag depends on speed, the body's cross‑sectional area, shape and smoothness, and the water’s density and viscosity. A useful way to think about it is that drag increases with the square of speed and scales with a drag coefficient and area. Animals reduce drag through streamlined shapes and smooth surfaces to minimize both friction and form drag. The other terms describe different concepts: a camouflage pattern, a phylum, and a structural polysaccharide, none of which capture the resistive force experienced during movement through water.