(Taxonomy (from Ancient Greek: taxis "arrangement" and Ancient Greek: nomia "method") is the practice and science of classification.
Taxonomy uses taxonomic units, known as taxa (singular taxon). In addition, the word is also used as a count noun: a taxonomy, or taxonomic scheme, is a particular classification ("the taxonomy of ..."), arranged in a hierarchical structure. Typically this is organized by supertype-subtype relationships, also called generalization-specialization relationships, or less formally, parent-child relationships.
In such an inheritance relationship, the subtype by definition has the same properties, behaviors, and constraints as the supertype plus one or more additional properties, behaviors, or constraints. For example: car is a subtype of vehicle, so any car is also a vehicle, but not every vehicle is a car.
Therefore a type needs to satisfy more constraints to be a car than to be a vehicle. Another example: any shirt is also a piece of clothing, but not every piece of clothing is a shirt. Hence, a type must satisfy more parameters to be a shirt than to be a piece of clothing.
Taxonomists divide animals into about 33 major groups, called phyla.
What's phyla? Again from Wikipedia:
In biology, a phylum (English pronunciation: fie-la, plural: phyla) is a taxonomic rank below Kingdom and above Class. "Phylum" is equivalent to the botanical term "division." The kingdom Animalia contains approximately 40 phyla; the kingdom Plantae contains 12 divisions. Current research in phylogenetics is uncovering the relationships between phyla, which are contained in larger "clades", like Ecdysozoa and Embryophyta.
And no, I'm not going to present a definition of "clades". As you can see, oceanography, like any other profession, has a great deal of terminology to learn. I'll talk about "clades" in my next post.
To continue:
Each phylum represents a distict body plan. The difference between phyla is much greater than the difference between species within an individual phylum.
Out of all these phyla, only one has no representatives in the ocean, the little velvet worms called onychphorans.
On the other hand, there are 14 phyla that are only found in the ocean.
The large scale diversity of animals in the oceans far outshines that on land. Even though the number of identified species on land is much higherr than that in the oceans, this number is deceptive, as new ocean organisms continue to be discovered.
For example, in 1988, scientists realized that what had been viewed as just two species of commercially valuable deep-sea crabs was really 18 different species.
Every year brings similar findings. In 2001, a 23-foot long squid unlike any known species was discovered. In 2003, it was Big Red, a bloodred, two- to three-foot long jellyfish with no tentacles. In 2004, a hot-dog sized species of dragonfish was found. This was found on a trip to the relatively well-studied Bear Seamount off New England.
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Bibliography:
Ocean Science 101 by Jennifer Hoffman
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