English practice 9

Light Bright, Light Bright: Turn on the Magic of Colored Light As a child, I used to catch fireflies at dusk when I was young.₁ I remember feeling a strange excitement which,₂ looking into my cupped hands, I would see the light grow brighter then dimmer as the fly flitted from one side to the other, trying to find an escape. What I should have felt, however, was amazement at the biological wonder I saw before me: bioluminescence.

Bioluminescence literally means "living light," and it refers₃ to a strange adaptation found in some organisms. It allows these organisms to create a chemical reaction that generates and emits light. Even though scientists know₄ that this light is not intended to be a heat source, they're not totally certain what it is intended to do, either. Theorists hypothesize that organisms use their self-manufactured light for camouflaging themselves, illuminate₅ their surroundings, attract mates and prey, repulse predators, and communicate.₆ This bioluminescence shines through in everything from Star Wars Anakin Skywalker, to X-Men's Wolverine, to Twilight's brooding vampire Edward Cullen.

The number of terrestrial or land-based, organisms₇ that exhibit bioluminescence is rather small, and many, such as fireflies and spiders, are fairly small in stature. In fact, the vast majority are single-cell organisms that cannot be seen with the naked eye. Unlike these smaller organisms, researchers are puzzled as to why most animals and humans did₈ not evolve this unique trait. Apparently the adaptation was not universally necessary, given the bright rays of the sun that bathed the surface year-round.₉

In the ocean, bioluminescence becomes far more prevalent. The deeper an organism lives in the ocean, the more likely it is to produce light. Many organisms glow green but₁₀ some produce red or yellow light. Its₁₁ purpose might be to light the way below the surface thanks of these organism's lights, even though₁₂ almost no visible light can penetrate to that level.

The extreme depth at which most of these organisms exist represents the biggest obstacle researchers face in determining the primary function of bioluminescence. Undoubtedly, this will slow the pace of exploration more then₁₃ lack of money. For that reason, it may be some time before this mysterious adaptation is clarified.₁₄₁₅

In America, we take many things for granted. If we don't feel well, we see a doctor. If we're hungry, we eat something. If we're thirsty, we drink some water. These very basic actions can be amazingly difficult, if not impossible, in some parts of the world.