Whales Essay

Intraspecific Evolution in Whales
Whales are notable for being mammals which are fully adapted to oceanic life. These are three groups of Whales in their phylogenetic tree; Archaeocetes, Mysticeti and Odontoceti. The first group are known from their fossils and are seen to be a transitionary form as they retained a number of features associated with land mammals e.g. hind limbs with feet and limbs. The two other groups diverged around the start of the Oligocene; when the ice caps started to grow in the poles of the earth. It has been suggested that this may be due to the rise of seasonal planktonic production which could have led to specialisation (Houben, 2013); this ties in nicely with other summarisations which link the diversions of Whales in this time period. Mysticeti and Odontoceti differ on two counts; Mysticeti possess baleen making them filter feeders of plankton, in comparison Odontoceti possess a single set of teeth and have the ability to echolocate.
I am going to concentrate on Killer Whales, showing their evolution within the species. Research in this area began in 1970 in the area of British Columbia, Washington and Alaska which set out a formula for which all other studies have followed. There are three types of Orcas; Resident, Transient and Off-shore (Bigg, 1982). They differ in terms of acoustic receptors, diet, behaviour, dorsal fin shapes, geographic range, reproduction and social organisation. The resident and transient are very well understood, with the off shore not that well studied. There are various differences between populations of Orcas around the world who have various adaptions to their particular environment.
In terms of studies of orcas it must be noted that most of the data has been gathered fr...

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...9. Orca reasearch trust.
Please note I have referenced Bigg 1982 in the second paragraph; the paper is not available online nor on anything off the university library. I had contacted the Centre for Whale Research who had copies of the paper but I had to contact them and they would send it onto me which they didn’t. but it is well established that in the paper it was outlined the three types of killer whale, their feeding habits, social orgainisation, movement patterns which were later confirmed by later research. I have referenced a number of papers by John K.B. Ford who is from the same organisation. I would have referenced 3 other papers from 1986, 1987 and 1990 also by Bigg had I received the PDF’s.
The name of the paper is; An assessment of killer whale (Orcinus orca) stocks off Vancouver Island, British Columbia. Rep. Int. Whal. Commn. 32:655-666, M.A. Bigg.