It can’t be a coincidence that almost all of them have red blood. Why can’t it be blue? Green? Purple?
In: Biology
It’s the haemoglobin; the way in which animal life evolved requires transportation of oxygen around the body. Blood can do that, and the substance within the red blood cells that absorbs oxygen when you breathe in is a protein called haemoglobin. It has iron in it, and oxidised iron is red.
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