Magoosh Toefl — Reading Practice __exclusive__

A) It attracts prey by mimicking smaller organisms. B) It produces sudden bright flashes to startle attackers. C) It helps them match light from above to avoid detection from below. D) It allows them to signal potential mates across long distances. C Explanation: The passage states that hatchetfish use photophores along their undersides to match downwelling light, erasing their silhouette from below and hiding from predators.

Bioluminescence in the deep sea serves several adaptive functions. One of the most common is counter-illumination camouflage. Many species, such as the hatchetfish, possess light organs called photophores along their undersides. By matching the dim downwelling light from the surface, these fish effectively erase their silhouette when viewed from below, hiding from predators. Conversely, some predators use bioluminescence as a lure. The anglerfish, for example, dangles a glowing appendage in front of its mouth to attract small prey. In other species, sudden flashes of light startle or temporarily blind attackers, providing a critical escape window. magoosh toefl reading practice

The deep ocean, defined as depths below 200 meters, exists in perpetual darkness. Sunlight cannot penetrate this far, yet the region teems with life. To navigate, hunt, and mate in this lightless environment, many species have evolved bioluminescence—the production and emission of light by a living organism. Unlike the bioluminescence seen in fireflies, which occurs on land, deep-sea bioluminescence is almost exclusively blue-green in color, because these wavelengths travel farthest in seawater. A) It attracts prey by mimicking smaller organisms

Perhaps the most intriguing use of bioluminescence is in communication. Research conducted in the 1990s aboard submersible vehicles revealed that many deep-sea organisms produce species-specific flash patterns. These patterns help individuals recognize members of their own species for mating, avoid hybridization, and even coordinate group movements. Squid, shrimp, and certain jellyfish have all demonstrated the ability to alter the duration, frequency, and intensity of their light pulses. D) It allows them to signal potential mates

However, this form of communication carries risks. Predators may eavesdrop on these light signals, detecting prey that flash too frequently or brightly. In response, some species have evolved “private channels” by producing light outside the visual range of common predators or by using extremely brief flashes that are difficult to locate. As one marine biologist noted, “In the deep sea, every light signal is a gamble between being understood by a friend and being eaten by an enemy.” 1. According to paragraph 2, how does counter-illumination camouflage benefit hatchetfish?