Have you ever looked at an animal and tried to figure out what it is? What group it belongs to? Which animals you already know that are most like it? What animals would be descendants from the same ancestors? When you think of a group of animals, take birds for example, what characteristics make them "birds"? Is it Flight? If so, then are flying squirrels or flying fish, birds? How about insects? Are they birds? OK, here's another question. Penguins? They can't fly, but they are birds. Gets tricky, doesn't it.
Well scientists have been arguing over how to classify plants and animals for centuries. What they have come up with is a pretty good system for placing living things in groups, based on their similarities. The more similar their features, the smaller the group. Their struggles over the simple question of how to classify plants and animals have led them to all sorts of discoveries about the plants and animals they have studied.
The system they came up with is called the taxonomic system or "taxonomy". Think of it like this: individual life-forms (species) that are very similar are classified in small groups (genus). These small groups have similar characteristics to other genuses, which belong to the same family. Families belong to orders, orders to classes, and classes to phylums. And, finally, phylums belong to a kingdom. The two main kingdoms are plants and animals. Here's the way this looks, when you look at it from the top, down - like an outline. Imagine under each of the two kingdoms, multiple phylums and under each phylum, multiple classes, etc.
Now, lets give some names to some of the more popular groups and lets see if you recognize them. Remember, scientist like to use Latin, so some of these names might sound a little strange, but most of the large groups have common English names that sound very similar. First, animals belong to the kingdom, "Animalia". OK, thats not too hard - it sounds a lot like "Animal". Now, how about some of the more common phylums:Phylum Examples
The phylum Chordata contains most of the land animals that you know, as well
as some well known (and not so well known) marine animals. First it has two
interesting subphyla: Urochordata (Tunicates: sea grapes, sea squirts, etc.)
and Vertebrata. These are some examples of classes in the subphylum
Chrondricthyes (Rays and Sharks)
Osteichthyes (Bony Fish)
Reptilia (Sea Turtles, Alligators)
Mammals (Marine mammals: whales, dolphins, porpoise, manatees)
There are many other phyla and classes that aren't mentioned here. But this will give you an introduction to the study of marine biology. As you spend more time around the water, you will appreciate more and more the infinite variety of life and the commonalities that connect it all together.