Commensalism is the term you are looking for
Answer:
Moist walls - gases dissolve in the moisture helping them to pass across the gas exchange surface. Permeable walls - allow gases to pass through. Extensive blood supply - ensuring oxygen rich blood is taken away from the lungs and carbon dioxide rich blood is taken to the lungs.
I attached a picture showing how to do it
The genotype for both parents is Br. if using B= black and r = red
