2015 unit 1, as biology exam question ocrWatch this thread
I managed to scramble an answer together that said something like: the baby gets oxygen from the mothers placenta, so doesn't need the lungs(pulmonary system), so that's why the hole went through the atria...
Dunno if it's right
Wondering what everyone else got
Yes I got something similar, they don't use their lungs so there is no need for a double circulatory system. By having a hole from one atria to another created a single circulatory system, as the blood isn't pumped to the lungs, just the body.