biology aqa aslevel question

Seals are diving mammals. They fill their lungs with air before they dive and hold their breath during the dive. Figure 3 (https://filestore.aqa.org.uk/sample-papers-and-mark-schemes/2019/june/AQA-74012-QP-JUN19.PDF pg 8) shows the dissociation curves for seal oxyhaemoglobin and seal myoglobin. Myoglobin is an oxygen-carrying protein found in muscles.
Use information in Figure 3 to explain how the seal’s myoglobin dissociation curve shows the seal is adapted for diving.

the mark scheme says "1. High(er) affinity for O2", however isn't it the opposite since the blood o2 conc is higher at a low o2 conc, so that means myoglobin loses o2 more easily?

Reply 1

0gg

The y-axis should really be "percent saturation" (of haemoglobin / myoglobin) since oxygen concentration is virtually the same thing as its partial pressure! Having "blood oxygen conc." on the y-axis makes it so much more confusing for no reason.