What is oxygen measured in in oxygen dissociation curves?

At low concentrations of oxygen, why is it harder for the molecule to load oxygen?

Once the first molecule of O2 is loaded..

If haemoglobin has a lot of oxygen it is called..
Similarly for when it doesn't have a lot of oxygen it's called..

What causes the shape of different haemoglobin molecules change?

The further to the left the dissociation curve...

The further to the right the dissociation curve...

What effect does the presence of carbon dioxide have on the affinity for oxygen?

In the lungs what is the dissociation for oxygen?

In the tissues what is the oxygen dissociation curve like?

What pH is dissolved carbon dioxide therefore what effect does this have on haemoglobin?

Therefore, if low pH changes the shape of the molecule so it releases oxygen more readily, what's the effect of high pH (low concentration of CO2) on the dissociation curve?

Describe the statement 'the more active the tissue, the more readily oxygen is unloaded'.

In a pregnant woman, where would the babies oxygen dissociation curve be?

What is the oxygen dissociation curve of a rat in comparison to a Plaice (that lives on the bottom of the sea).