On The Existence of Fish


‘There is no such thing as a fish.’

– The Encyclopaedia of Underwater Life


The Encyclopaedia of Underwater Life, edited by Andrew Campbell and John Dawes, published by Oxford University Press in 2005.

Taxonomic Hierarchy


In biology, every organism has several taxonomic classifications; these classifications are taken from the taxonomic hierarchy. This hierarchical tree displays how all Earth organisms are related to each other.

Biological ClassificationTo illustrate this hierarchical tree, imagine a daffodil, ladybug, goldfish, human, cat, fox, jackal and dog.

Regio
Out of the three Domains that make up Life on Earth, the Eukarya is the most diverse domain. (The other two Domains are that of the Archaea, a group of single-celled organisms, and that of the Bacteria, very small organisms whose cells do not have a nucleus.)

This Eukarya Domain includes all organisms with complex cells, or a single cell with a complex structure; in these cells the genetic material is organized into chromosomes in the cell nucleus. Obviously, this includes the life forms listed above.

Regnum
The Eukarya Domain is made up of Kingdoms; the Animal Kingdom being the most well known. This Kingdom includes all the animals listed above, from ladybug to dog, but excludes a plant like the daffodil.

Phylum
The Animal Kingdom is made up of Phyla; the Phylum Chordata is one of the most interesting Phyla because it includes all vertebrates. That is to say, all mammals, fish, amphibians, reptiles, birds – to name a few – are part of this Phylum. Note that the ladybug is not part of this Phylum.

Classis
The Chordata Phylum is made up of Classes; the Mammal Class being the most dominant on Earth. Humans, cats, foxes, jackals, dogs and all other animals who suckle their young are part of this Class. This excludes the goldfish.

“If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man.”
– Mark Twain

Ordo
The Class of Mammals is made up of Orders; if we take the Order of Carnivora, the carnivores, we would exclude human beings (who are the story telling member of the Order Primates, in the Family of the Hominidae, of the Genus Homo). This leaves us with the cat, fox, jackal and dog.

Familia
The Order of Carnivora is made up of Families; the fox, jackal and dog are part of the Family Canidae. That is, all dog-like animals. This excludes the cat.

Genus
The Family Canidae is made up of Genera. (The term comes from the Latin genus meaning “descent, family, type, gender”; from the Ancient Greek: γένος, “race, stock, kin”.) In our example, the fox is part of a different Genus than the jackal and the dog.

Species
The Genus Canis is made up of Species; the most widely accepted definition of a species is ‘the largest group of organisms capable of interbreeding and producing fertile offspring’. That brings us to the difference between a jackal (canis aureus) and a dog (canis lupus), who are part of the same genus, but are different species.

“Outside of a dog, a book is man’s best friend. Inside of a dog it’s too dark to read.”
– Groucho Marx