Electron microscope image of plankton
“What we’re looking at is just a shell, made mostly of calcium carbonate (just like a snail’s shell, except that it’s made up of a number of separate plates). Inside, there’s a relatively ordinary single-celled alga called a coccolithophore. Most coccolithophore species are not quite as regular.The weird bit is that, despite being hugely successful, found in great numbers in every ocean on earth, nobody knows exactly why they go to the trouble of making complicated exoskeletons.”
“Fun fact: chalk is made almost entirely of coccoliths (I’m talking about the stuff the White Cliffs of Dover are made of; the stuff used on chalkboards not usually real chalk these days).“