Marine Biology

Why a Whale is not a Fish

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"Why a Whale is not a Fish"
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Although whales and fish both live in water, this is the only way in which they are the same. There are a multitude of features which determine the difference between a fish and a whale, which includes such details as scientific classification, biological structure and modes of communication. All of the above features, once explained, will give an idea of why a whale is not a fish.

Firstly, whales (which incidentally includes porpoises and dolphins) fall into the order of mammals called Cetacea, which is a grouping of mammals that live in water. There are two subgroups, namely Baleen whales and Toothed whales, and within these groups, one will find less than a hundred different species, 65 of which are toothed. To offer an idea of where the similarities between fish and whales end, one would have to look at the classification of the Phylum Chordata subphylum vertebrata, which is the grouping of animals with backbone. This is where whales and fish begin to become separated in terms of classification. Some fish fall into the superclass Agnatha, and others, as well as mammals, fall into the superclass Gnathostomata. After this, animals are grouped into classes. Fish, of which there are over 28 000 species, fall into four classes, whilst all mammals fall into one class. The order of cetaceans is to be found in the class mammalia. This divergence should illustrate how different whales are from fish.

The reason that fish and whales are classified so differently is entirely based on biological structure. To begin with, whales, porpoises and dolphins all give birth to live young which are gestated inside the womb of the animal from the moment of fertilisation. Fish, however, mostly lay eggs, which are fertilised and gestate outside the mother's body. There are exceptions to this, but they only serve to prove the rule. Further, whales, like all mammals, breath air. They take in air through a blowhole in the top of the head and this air travels to the lungs, which then aerate the blood. Fish cannot survive by breathing air. They absorb air out of the water they take in through their gills. These methods of respiration are quite clearly very different. Finally, although to a first-time viewer, fish and whales may appear similar, on closer inspection one will notice that the swimming motion of a whale is completely opposite to that of a fish, as is the tail movement. Whales will swim in an up-and-down motion through the water, with the horizontally-oriented fluke propelling the whale from behind. Fish swim through the water in a side-to-side motion, propelled from behind by a vertically-oriented tail fin. These variations in mode of travel should also further illustrate the difference between fish and whale.

Lastly, whales are capable of verbal communication through sounds made in the throat and head, whereas fish only communicate through body language. Whale song has been recorded to go on for as long as half an hour at a stretch, and it has been theorised that this song is a means of communication between whales for a variety of purposes. Bottle-nosed dolphins which have been kept in aquariums have been trained to recognise a limited vocabulary, and can respond as well, in a repetitive pattern of clicks and squeals. This has never been achieved in an aquarium with any kind of fish.

On the whole, when whales are examined closely in terms of biology, social structure and communication, they will be found to be remarkably different from fish. Scientific evidence supports this differentiation, and so does scientific taxonomic classification of the species. It is evident that whales are much closer to mammals in every way, other than their habitat, which is the one commonality they share with fish.       


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