Reading: True / False / Not Given: Question 1

Bioluminescence, the production of light by living organisms through internal chemical reactions, occurs in a remarkable range of species, from fireflies and glow-worms to fungi and, most abundantly, marine organisms. It is estimated that more than three-quarters of deep-sea creatures collected from depths below 700 metres are capable of producing their own light, making bioluminescence one of the most common forms of communication in that lightless environment. The chemical process typically involves a light-emitting molecule called luciferin reacting with oxygen in the presence of an enzyme, luciferase; the reaction releases energy as a photon of light rather than as heat, which is why the light produced by living organisms is often described as "cold light."

Marine biologists have identified several distinct purposes for bioluminescence among ocean species. Some organisms, such as certain species of anglerfish, use a glowing lure to attract prey close enough to be captured. Others rely on a sudden burst of light as a defensive tactic: when startled, some squid release a cloud of luminous ink to disorient a predator and gain time to escape. A third function is intraspecies signalling, several species of lanternfish possess characteristic patterns of light-producing organs, or photophores, arranged along their bodies in configurations that appear to help individuals recognise members of their own species in the dark.

Despite decades of study, several aspects of bioluminescence remain poorly understood. Researchers have yet to determine, for instance, why some deep-sea species that never encounter sunlight retain vestigial eyes capable of detecting light at all, while other species in the same habitat have lost their eyes' image-forming capacity entirely and instead rely on simple light-sensitive patches. What is clear is that the ocean's midwater zone, far from being a dark and empty void, is illuminated by a constant, shifting traffic of biological signals invisible to any observer without specialised low-light equipment.

Do the following statements agree with the information given in the passage? Write TRUE, FALSE or NOT GIVEN.

1. More than three-quarters of deep-sea creatures collected from below 700 metres can produce their own light.
2. The chemical reaction responsible for bioluminescence releases most of its energy as heat.
3. Anglerfish use a glowing lure to draw prey within reach.
4. Squid release luminous ink mainly in order to hunt prey rather than to escape from predators.
5. Bioluminescence has been observed in freshwater fish species.
6. Patterns of photophores on lanternfish may help individuals identify others of the same species.
7. Scientists have identified more functions for bioluminescence in shallow-water species than in deep-sea species.
8. Researchers have fully explained why some deep-sea species retain light-detecting eyes while others have lost image-forming vision entirely.