Passage I

Fin whales engulf and filter massive amounts of water and prey during an event called lunge feeding. The 5 distinct stages of a lunge-feeding event are listed and described below.

Stage 1: Rapid acceleration of the whale

·Stage 2: Mouth opening and engulfment

·Stage 3: Onset of mouth closure

·Stage 4: Continued mouth closure and pre-purging

·Stage 5: Purging (filtering water from prey)

The figure below shows how a fin whale's speed and gape angle (angle between the top and the bottom of the fin whale's mouth) varied during a lunge-feeding event.

Figure adapted from J.Potvin et al., “Passive Versus Active Engulfment: Verdict from Trajectory Simulations of Lunge-Feeding Fin Whales Balaenoptera physalus."©2009 by The Royal Society.

6. Which of the following statements best explains why the speed of the fin whale decreased during Stage 2? During Stage 2, the cross-sectional area of the whale’s mouth was:

Answer and Explanation

Your Answer is

Correct Answer is G

Explanation

It can be seen from the figure that the gape angle starts to increase from stage 2, indicating that the fin whale is opening its mouth. Opening the mouth will destroy the overall streamline shape of the fish body, resulting in an increase in the cross-sectional area, thereby increasing resistance and reducing swimming speed