Responses to the Environment Practice Test

A student observes that when a loud sound occurs near a flock of pigeons, most birds take flight within 1–2 seconds. Heart rate measured from a few trained birds increases immediately during the sound and returns near baseline several minutes after the sound stops. No changes in body size or feather structure occur. Which response best explains the rapid increase in heart rate during the loud sound?

A plant is placed near a window so light comes from one side. Over the next 24 hours, the stem bends toward the light source while the plant remains rooted in place. When the pot is rotated 180°, the stem gradually bends in the new direction of the light. No new leaves form during the observation period. Which response best explains the stem bending toward the light?