Oxygen compromises about 47 percentby weight of earth's continental crust. Another important element is silicon. Continental crusts are older and less dense when compared to the oceanic crust.
The most important way that the pH of the blood is kept relatively constant is by buffers dissolved in the blood. Other organs help enhance the homeostatic function of the buffers.
el niño tendría síndrome de downEl síndrome de Down es causado por un error aleatorio en la división de las células que tiene como resultado la presencia de una copia extra del cromosoma 21.