Blue blood

The phrase (or 'term'?? not too sure what you mean) "blue blood" is about an aristocratic man. Scientists say that the human blood is red in colour, because the blood has hemoglobin in which contains ions of iron. Some mollusks and arthropods has have hemocyanin in their blood. Hemocyanin has ions of copper, which gives them their blue colour.

Very advanced piece of writing- great work! Only thing I'm not sure about is the first sentence... depending on what you mean, you may be better off saying;

'The term 'blue blood' is used when talking about an aristocratic man'

But I'll leave that up to you :)