|Consider The Penguin |
Information compiled from various web sites
By Ed Decker
Amidst all the recent talk about Evolution versus Intelligent Design and Creationism, a movie about the lives of the Antarctic Penguins hit the theatres and found great success and wide audience with families across the nation. It certainly has been a breather from the sex, violence and gore of the rest of the field.
However, I could not help but reflect on the absolute impossibility of any Penguin specie evolving from its embryonic shell to become the creature it is today. Here are some facts I gleaned from the web about this strange creature.
Penguins are flightless birds belonging to the family Spheniscidae. World-wide there are 17 species of penguin, all of which breed in the Southern hemisphere.
Penguins differ from birds which are able to fly, by having a much heavier and more robust skeleton. Birds that fly must have a skeleton which is as light as possible, in order to make flight possible. This is achieved through bones that are paper-thin or hollow, often with internal honeycombing that combines adequate strength with low weight.
For penguins, such light weight skeletons hold no advantage, and they therefore have bones which are considerably denser, giving greater strength and reduced buoyancy. This is not something they evolve into over thousands of generations.
Penguins' bones are solid and heavy, which help them to remain submerged and reduce the energy needed for pursuit diving. Some species can reach depths of 1000 feet or more and stay submerged for up to 25 minutes, though most prefer shorter, shallower dives. They would never have survived without their food source and they could never have reached their food source without their heavy bones.
Penguins also have a counter-current heat exchange system in the nasal passages, whereby air from inhalation and expiration are mixed in a common chamber. This allows recovery of much of the heat lost from the blood capillaries during respiration. This process can also be reversed to aid heat loss during periods of hot weather.
They mostly have blackish upperparts and whitish underparts on both the abdomen and flippers. This helps to camouflage the penguin against the lighter sky when viewed from below, and the darker waters when viewed from above, making them harder to spot by both predators and prey. Again, this had to be there at the ‘start.’
The feathers are waterproof and interlocking, providing an effective barrier to water. Each feather has small muscles which allow them to be held tightly down against the body whilst swimming, to form a thin water proof layer. Little air is therefore trapped in the plumage when swimming, preventing excessive buoyancy which would hinder diving. When on land, these muscles hold the feathers erect, thereby trapping a thick layer of warm air to provide the best insulation against cold wind.
The insulation provided by the plumage is further aided by thick fat deposits beneath the skin, and a counter-current blood supply to the exposed legs and feet. The blood vessels supplying warm blood to the legs and feet are surrounded by the vessels returning cooler blood back to the body, enabling much of the heat lost from the warm blood to be recovered.
This vascular system is also able to severely restrict the amount of blood flowing to the flippers and feet, which may be kept as low as 6 Celsius despite a body core temperature of 39 Celsius. This considerably reduces the amount of heat lost during cold weather, but the process can also be reversed so as to aid heat loss during hot weather.
Penguins dive in search of prey, and then having located it they chase it, and swallow it whole under water. To locate and capture prey therefore requires good underwater vision, but the differing refractive indexes of water and air require different shaped lenses. Penguins therefore are able to alter the shape of the lens considerably, enabling them to compensate for the differences in refractive index, and allowing good vision in air and water.
The penguins face the problem of being unable to breathe underwater. Having a relatively small body size compared to seals and cetaceans, penguins are more restricted in the amount of oxygen that they can store to sustain them during underwater dives. The underwater pressure compresses the air held in the lungs and air-sacs, and consequently these airways only provide about a third of the oxygen requirements needed for each dive.
The haemoglobin in red blood cells holds a certain amount of oxygen in all animals, in order to circulate oxygen from the lungs to all parts of the body. In penguins, the blood has a much higher concentration of haem oglobin than is necessary solely for circulatory needs, and this is used as an oxygen store during underwater dives. In addition the muscle tissues have high concentrations of myoglobin, which also stores oxygen in the very place that it is most needed for underwater swimming.
As oxygen is used up during respiration, carbohydrates and fats are burned off to provide energy, and the by-product of this process is carbon dioxide. During underwater dives this carbon dioxide builds up in the blood stream due to the lack of fresh air entering the lungs and air-sacs. Under normal circumstances this excess carbon dioxide would combine with the blood to become carbonic acid, raising the acidity of the blood. Even small increases in the acidity of the blood can be metabolically damaging, and penguins therefore have an ability to buffer the blood, preventing it from becoming too acidic in the presence of increased levels of carbon dioxide.
The Penguin beak has a osseous system, built up from the jawbone. It has several tight horn-plates from keratin, like our nails and hair. And then many species have at the end a pine grosbeak and the cutting edge is sharp. This allows a penguin to hold and kill a slimy fish. On their tongue and palate, you can see backwards pointed protuberances, acting like barbed hooks to prevent the escaping of a prey.
By comparison to adults, chicks have very different types of plumage, which serve completely different purposes. Newly hatched chicks have a protoptile plumage, which is very sparse, and provides inadequate insulation from the cold. However, at this period of development chicks do not require insulation, because they are brooded by the adult, and the sparse plumage enables rapid transfer of heat from the adult brood patch to the chick. Only when chicks near the end of the brood period, do they need a plumage with greater insulative properties.
When the chicks reach about two weeks of age, the original protoptile plumage, which is thin and readily transmits warmth from the parent bird, is replaced by a thicker mesoptile plumage. This provides good insulation, and in association with metabolic changes, it allows the chick to maintain its own body temperature.
As chicks grow larger, and demand more food, it is necessary for both adults to go to sea to forage. Prior to being left by both adults, chicks grow a thick, fluffy plumage called the mesoptile plumage, which traps a thick layer of air and provides excellent insulation. This plumage provides better insulation against cold wind than the adult plumage, however it is not waterproof and is only effective when dry.
Normally this is not a problem, since chicks do not enter the water at this stage. The insulation properties of the mesoptile plumage can be seen in breeding colonies during periods of hot weather when chicks often suffer from heat stress. By contrast, the breakdown of this insulation when wet is evident during periods of heavy rain, when some chicks can become saturated, and die from hypothermia.
When the chick becomes fully developed, further physiological changes occur, and the mesoptile plumage is shed and replaced by a waterproof plumage similar to that of the adults. This plumage needs to be kept waterproof in order to maintain an adequate level of insulation at sea, and in order to retain these properties, the plumage must be renewed regularly throughout adult life. This is usually performed during an annual moult, when birds come ashore for a period of 2 - 4 weeks, while old feathers are pushed out by the new ones growing from underneath.
The waterproofing qualities of the adult plumage is maintained by constant preening. A waxy substance is produced from the uropygial gland at the base of the tail, and this is spread onto the feathers during preening to maintain their waterproofing qualities. Preening also realigns the feathers, which interlock through microscopic hooks.
Even despite these adaptations, penguins are often unable to hold sufficient oxygen to sustain the deepest dives, and they have therefore evolved physiological adaptations that enable them to use anaerobic respiration (the production of energy in the absence of oxygen). In humans, when muscles become overworked and lack sufficient oxygen to sustain their energy requirements, the build up of lactic acid resulting from anaerobic respiration quickly causes pain and muscle fatigue. In penguins however, the muscle tissues contain high levels of an enzyme called lactate dehydrogenase which allows muscles to continue working anaerobically, by neutralising the build up of lactic acid. This lactic acid is later expelled from the body when normal breathing is resumed, during periods of surface rest or shallow diving.
Finally, we need to consider the weather in which this 3 million to 15 million years, [depending on who you ask] eons-long process would have taken place. We are talking cold here, cold enough to freeze anything that sat out in it for more than a few minutes.
The Penguin, no matter how well into evolution it could ever be, could not have survived the first winter without ALL the above things working perfectly.
Winter: -40 to -94°F (-40 to -70°C) ************************************
Summer: -5 to -31°F (-15 to 35°C)
(c) copyright 2005, 2009 Ed Decker, all rights reserved