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Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about a fascinating phenomenon known as bioluminescence, the ability of living organisms to produce light. While most of us think of fireflies, bioluminescence is actually far more common in the deep ocean. Over 90% of creatures living below 700 meters generate their own light. Why? Well, there are several purposes. Some species use it to attract prey, like the anglerfish, which dangles a glowing lure. Others use it for defense, such as squid that release a cloud of glowing particles to confuse predators. But perhaps the most intriguing use is for communication. For example, some shrimp produce light in specific patterns to signal mates or warn rivals. Interestingly, scientists have discovered that bioluminescence is not just a chemical reaction; it's highly efficient, converting nearly 100% of energy into light, unlike an incandescent bulb, which wastes most energy as heat. This efficiency has inspired research in medical imaging and sustainable lighting. So, next time you see a firefly, remember that it shares a deep ocean secret.