When Bing's homepage glows, a starlit bay or a lantern-lit deep sea, a bioluminescence quiz often follows. It's one of the more magical science topics, and the questions revolve around which creatures glow and why.
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What bioluminescence is
Bioluminescence is light produced by a living organism through a chemical reaction, typically a molecule called luciferin reacting with an enzyme, luciferase, and oxygen. Crucially it's 'cold light', almost no heat is released, which is a favourite quiz distinction from a regular bulb.
The creatures that glow
Fireflies (actually beetles) flash to attract mates. The deep-sea anglerfish dangles a glowing lure. Glow-worms line cave ceilings, New Zealand's Waitomo Caves being famous. And glowing plankton, dinoflagellates, light up breaking waves and bays in electric blue.
Why they do it
Attracting mates, luring prey, and startling or confusing predators are the three main reasons. Some squid use light as camouflage, matching the glow above to hide their silhouette, called counter-illumination, a great trick question.
Answering approach
Identify the organism from the caption, then the 'why' usually follows, mate, prey, or defence. For the chemistry question, luciferin plus luciferase and oxygen equals cold light is the reliable answer.
Frequently Asked Questions
What causes bioluminescence?
A chemical reaction between luciferin and the enzyme luciferase with oxygen, producing 'cold light' with almost no heat.
Which animals are bioluminescent?
Fireflies, deep-sea anglerfish, glow-worms and glowing plankton (dinoflagellates) are the classic examples.
Why do animals glow?
Mainly to attract mates, lure prey, or defend against predators; some squid use light as camouflage.