Decoding the logo
It wasn’t planned this way, but the Talk Science logo has become a sort of test (a fun one, we hope). Pretty much everyone can identify what’s in the first circle. Far fewer can tell at a glance what the second one contains (only one person has gotten it right the first time). And I don’t think we’ve ever had anyone name the item in the third circle right away, although occasionally someone comes close.
This is, of course, a cephalopod. An octopus, to be specific. Octopuses (that is how we pluralize it here) are a nearly endless source of weird biology facts. They have three hearts and no skeleton, and their brains are widely distributed throughout their extremely compressible bodies. And they’re smart. There’s debate about precisely how smart and in what ways, but their behaviour demonstrates remarkable adaptability and complexity.
This one is harder. My first guess was a fungus of some kind, and I gather that’s a common choice. In fact, it’s a diatom—an alga that appears in aquatic environments around the world. Diatoms are distinguished by the elegantly geometric shapes of their silica shells. Like some of their ancestors and contemporaries, they contribute more resources to the biosphere than they consume. This makes their presence or absence one indicator of the overall health of the ecosystems in which they occur.
This is the one that seems to stump everyone. The major temptation for a non-biologist is to fixate on the helical structure in the foreground and reason that this must be some kind of DNA. I got taken in that way, but as any biochem student can probably tell you, that’s not a double helix—it’s an alpha helix. And anyone who can tell that can probably also tell you that this is a protein. One person guessed it’s a heme, which is close but not quite right. Technically there’s a heme in the picture, but it’s part of a larger molecule.
The exact identity of the molecule in circle number three is cytochrome c. Like many other hemes, cytochrome c functions in organisms as an electron transport. In the case of humans, that means it’s part of the production of ATP, which carries energy in your cells. All of the energy your body will ever use is available to you because of this process.
We’re not the only organisms with cytochrome c, though. Almost all other animals on Earth have it—as do most plants; they use it in photosynthesis. Microorganisms have it too. Trace back far enough to find the origin of cytochrome c, and you’re near the beginning of life. From an evolutionary perspective, this molecule is very strong piece of evidence in support of universal common descent.
The whole thing
Why these three? For the most part, they were chosen because they’re visually evocative and scientifically notable, and because our founder is a biology geek at heart. They also form a simple series that goes down in scale, from a complex multicellular organism down to single molecule that evokes the interrelatedness of all life on Earth.