A penguin foams past the biology
Jumat, 23 Oktober 2009
A penguin foams past the biology.
A penguin is any bird that belongs to the Order Sphenisciformes. That would be a strict definition. But, that doesn't mean much to an individual upon inspection. First of all, a bird is any animal that is a homeothermic vertebrate animal with a pair of modified upper limbs that support or supported flight at one time in the evolutionary development of the animal. A penguin would be any animal that belongs to the class Aves, which contains all birds, is incapable of flight due to loss of the proper machinery, is naturally restricted to the Southern Hemisphere, moves about by swiming and walking, nests on land, and shares similar morphological features -- mainly color and striping patterns -- between the sexes.
The origin of "penguin" is nebulous. Sources suggest that it comes from the Swedish alka from which the English "auk" was derived. From this term came the expression "great auk" or "penguin." However, both "great auk" and "penguin" did not describe what we know as penguins, rather great auks, another type of flightless bird (which happens to be extinct).
It is also theorized that "penguin" comes from the Welsh expression pen gwyn meaning "white head" or from the Latin pinguis, meaning "pin wing." Both these terms seem unlikely origins for the word "penguin," however. I don't think anyone knows.
The number will vary depending upon whom you ask. Some say at least 18; most say at least 17, while others admit to only 16 or as few as 13. I think there are 16, or at most 17, species. The issue of speciation is debated on whether certain populations are merely hybrids of two species or distinct species. Speciation is said to have occured when two populations of animals cease to breed and develop on their own evolutionary paths.
What is the question here is whether certain "species" of penguins are still capable of interbreeding. Two issues of contention are the Little blue penguin and White-flippered penguin whose morphologies are so similar that many will argue that they are conspecifics with subspecies differentiation. Others contest that the Fiordland and the Snares Island penguins are the same species and should be arranged into subspecies. Some say the Royal penguin is a geographically distinct race of the Macaroni penguin. Still others contest that the extent of differences in the genus Spheniscus does not merit their separation into four species (this is not a popular view).
Some biologists contest this designation of taxonomy. Others argue that penguins are so unlike other avian species that this arrangement is warranted. The biology and evolution of penguins is such that no other bird amongst the neornithes even closely resembles them. Because the penguin is unlikely to be relatives of these birds except distantly, scientists have placed them into their own order.
Basically, there is little evidence that penguins moved from any particular place to their current locations. Early fossil records date the arrival of penguins in the late Eocene - 37 million to 45 million years ago. Fossils of this period were found in Australia, New Zealand and Antarctica, all current locations of several modern day penguins. Some of these fossils suggest penguins were as tall as 6 feet! So, it is likely that a distant ancestor of penguins migrated, either by flight or by swimming, to the southern hemisphere. This common link between modern penguins and ancient flying relatives has not be found; only penguin-like fossils have been found in the southern hemisphere.
