The Oxygen Super Highway (Part 5)

There are myriads of arguments that successfully disprove evolution. There are just too many holes in the theory and it does not stand up under intense examination. It does not stand up under any examination. One of the basic assertions is that life originated in the water and proceeded onto land via a walking fish that mutated to walk and harvest oxygen from air instead of water. Just bringing up a theory like that draws suspicion.

Under normal atmospheric condition the air is made up of roughly 21% oxygen by volume and 0.03% carbon dioxide by volume. When the diaphragm contracts it moves down and draws air into the lungs by creating a vacuum within the body cavity. Air with this rich partial pressure of oxygen enters the lungs and fills tiny air sacs in the lungs called aveoli. Capillaries surround these aveoli and the thin walls of both allow the free exchange of gases. Now the blood flowing into the lungs is poor in oxygen and rich in carbon dioxide with percentage by volume of 5.3% and 5.9% respectively. With such vast differences in the partial pressure of gasses present diffusion rapidly occurs to equalize the partial pressures of gasses in the lungs and capillaries, so as the blood flows out of the lungs it has suddenly become 13.7% oxygen and 5.3% carbon dioxide by volume. So this is what is occurring - oxygen rich air flows into the lungs and comes into contact with oxygen poor blood. Due to the differences in pressure the oxygen flows into the blood and the carbon dioxide flows out of the blood which is rich in the blood and poor in the atmosphere. Oxygen rich blood is pumped out of the lungs, through the heart and out to the body tissues where it again flows through thin walled capillaries. The amount of oxygen and carbon dioxide in body tissues is 5.3% and 5.9% by volume respectively. Now diffusion occurs again and gas flows freely to equalize the differing partial pressures of gasses. The blood is returned to the 5.3% oxygen and 5.9% carbon dioxide by volume and pumped back to the lungs via the heart.

Now let us look at what happens in the gills of a fish. Water is much harder to harvest oxygen from because salt water only contains 0.4% to 0.8% oxygen by volume. Wow, what a difference from 21% by volume in the atmosphere! Water flows across fine filaments called lamellae where capillaries carry blood flowing in the opposite direction. The direction of flow is important to optimize diffusion in such an oxygen starved environment. Unfortunately I can not dazzle you with fancy numbers as with the human respiratory system, but the principle of blood flow coupled with diffusion remains the same. Newly oxygenated blood flows from the gills to body tissues that have a lower partial pressure of oxygen and a greater partial pressure of carbon dioxide and diffusion again redistributes the gasses.

One of the vital factors of a respiratory system utilizing gills is being immersed in water. Have you ever looked inside a washing machine full of clothes and water? All the clothes are suspended and separated from each other and the ventilation facilitates the removal of dirt from the clothes. When the wash cycle is finished the spun clothes hardly fill the drum, instead they are all pressed up against the sides. Gills can be likened to clothes in a washing machine. When they are fully ventilated, the water suspends and separates the gills allowing oxygen to diffuse across the membranes and oxygenate the blood in the capillaries, but when the fish is out of the water the gills look much like the clothes that have been spun - they hardly fill the cavity, instead they are all pressed together, up against the sides. That does not make for good oxygen exchange, in fact it does not make for any oxygen exchange. How about a human lung, or any mammalian lung for that matter? Water is some what detrimental to its function. Mammals are simply incapable of harvesting oxygen from fluid. Because of the nature of the oxygen demand and the content of oxygen in water, mammals will never be able to draw enough oxygen from water by the same means as from the air. Diffusion would happen in reverse of what it is supposed to!

How does a creature crawl out of the water that is dependant on water for its very life? Granted, there are such things as amphibians which take oxygen from water and from the atmosphere but we will take a closer look at that possibility after we have developed how amphibians do that. My contention is simply that no fish ever crawled out of the water and started living on land. There is a wall of separation between water and air! The mechanisms for oxygen exchange are just too different. On one hand water flows over an appendage type device and on the other hand gasses fill a sac. Could gasses ever flow over gills and oxygenate them? Then could those appendage type devices ever start to fold up into sacs? I find that very hard to believe. It is not something I am capable of taking on faith alone. Even if it did happen, it would have to be guided by something other than chance! A series of random mutations simply can not change gills into lungs. The very thing that would help a fish to survive in the atmosphere would kill it in the water and the thing that allows it to survive in the water kills it in the atmosphere. Because gills need to remain moist to function one of the developments required to allow it to begin to be used as a lung is a mucous membrane. What would the mutation have to be to create one of those out of the blue? It would never happen! Mucous glands are too complex to just appear out of no where and for no reason and DNA mutations are too simple. How can changing a few amino acids develop into brand new organs? Just bringing up a theory like that draws suspicion.