4. The relationship between the blood system and air pressure
we knew that there is a direct relation between the strength of blood system and the largeness of animals’ bodies. In away that, the greater the efficacy of blood system and the strength of the heart of animal, the bigger the size of its body. Because, by increase of the strength of blood system of the animal, it can over come the gravity easily and makes the blood to go higher and make its body larger.
But, there is a question. How far the increasing of the increase of heart and as a result the increase of its body’s size, can be continued? If an animal has a blood system with good efficacy and a strong heart, to what extent can get longer and enhance its body’s size?
Assume that we have a water pump, and we want to draw water from a well. The question is that: How much is the maximum depth, that we can draw water by this pump from the well?
According to Aristotle, it was possible; it was possible to draw the water by the pump from every depth. But the miners, who intended to send the out of the mine, noticed that, they couldn’t draw the water more than ten meters depth, even if they pump very hard. At the last years of his life Galileo became interested to this subject, but he couldn’t achieve a result, except for this result that the nature hates vacuity, to some extent. He thought that if he uses heavier liquid, wills this amount decrease or not? But before practicing this, he died. His student Torricelli examined this expe- rience in 1644. They conducted this examination with mercury, and they noticed that, they could lift it up to 76cm only in vacu- ity. They justified this, with air pressure and said that, the air around us have a pressure on the all the surfaces of the earth, the value of which is steady on the Earth, and this pressure causes the coming up of the water from the well through pumping, and because its strength is a clear amount, with what intensity we pump, it is not possible to draw the water more than ten meters (of course now, in deep wells float pumps are being used at the button of the wells and these pumps do not suck the water up- wards, but they push the water from down- ward).
If we suppose the heart of animals like a water pump, we can understand the importance of the air pressure around us. The heart has to pump the blood from lower parts of body. The air interference in this action, and when the heart dilates, it makes a vacuity in itself, and the air pressure, sends the blood toward the heart, by forc- ing on the surface of the body. As we knew, the force of the air pressure is a certain quantity, and the heart cannot lift up the blood from a certain amount, as the water pump was not able to lift up the water more than 10 meters.
The blood is heavier than the water, and its density is 1.6, that is, so ever strong is the heart, it is able to settle 6m above the ground. So we that the maximum size of animal’s body is interrelated with the amount of air pressure. Blood system has more efficiency in less gravity and high air pressure. So ever the strength of blood system is weaker; the animal is less able to overcome the gravity and its size become smaller. Also, if the animal has weak blood system, it has to live in a place that the air pressure is high. So the birds that have strong blood system and advanced respira- tory system can fly in high heights. Like Indian goose which flies at 9000m of sea surface where the air pressure in one third of the air pressure on the surface of sea. On earth, big mammals with strong blood system are able to live in most of earth and, they are tall and have large bodies. Reptiles, which have weaker hearts, can only lie on the ground. When amphibious are newborn and have a weak 2-chambered hearts, live in water, and when they obtain a strong and 3-chambered heart they can live on earth but with small bodies. Fish can live in water with 2-chambered heart, and it lies in the water.
The water is 800 times denser than the water and the pressure inside the water are by far more than that of the air. In different depths of water, the pressure is different, and for every 10m depth, one atmo- sphere is added to the pressure of the water. In deep areas of water, the pressure is very high, so we conclude that, the an- imals, which have weaker blood system, should be survived in depths of water. So, Coelacanth which is a primary fish, now it is able to live in very deep seas and if we bring it to less deep waters it will die within a short time.
Also the animals which have weaker blood system can be very large, only in very deep water. Like the largest crabs that live in a large deep sea. Because in it place there is so much pressure.
The above graph shows that:
The amount of air pressure, in the life time of the Sauropod, was higher than all other times.
Graph, such drawing , if air pressure does not change over time and was fixed.
The air pressure is an important factor that is setting the size of the largest animals on earth from past to now. The amount of air pressure is not constant over time. At the time of the dinosaurs, the air pressure has been much higher than now. If the air pressure be high in the now (as much as the dinosaurs time), current elephant size will be much larger.