Have you ever wondered how all the underwater species fit into the taxonomy biologists use to classify organisms? Back when I took high school biology, we learned it as the "tree of life". Everything was classified into seven levels of taxon (Kingdom, Phylum, Class, Order, Family, Genus, Species), and there were just plant and animal kingdoms. Of course, life is more complex than that, so there are a lot more levels now. With DNA sequencing, we're starting to figure out how things are actually related to each other. So it's a lot of fun to explore up and down and sideways. Which is what you can do here.

From any species page, you can click on the ▶ next to the scientific name for the species to see its full taxonomy from kingdom down to genus. Then you can click on any of those taxons to see what else is related. Want to try it? Here's a link to one of my favorite nudibranchs.

Some good taxons to start exploring are Pomacanthidae, the taxon for angelfishes. Or Pleocyemata, where lobsters, crabs, and shrimp all split off from each other. Or Scleractinia, hard corals.

Or you can start from the top of one of the kingdoms with species in this database:

• Animalia - Animals. This is what I have the most photos of. Remember that corals are actually animals.
• Bacteria - Bacteria. Most of these are too small to see, but some form larger structures that can look like algae.
• Chromista - Protists which have chlorophyll but aren't technically plants. Yeah, they look like plants.
• Plantae - Plants.