A seal is a mammal that lives mainly in the sea. Its breathing and respiration are very much like those of a human, but when it dives to chase and catch fish, it can remain underwater for as long as 20 minutes.
The graph shows how the percentage concentrations of oxygen and carbon dioxide, together with the concentration of lactic acid, change in a seal’s blood over a 40 minute period while it dives to hunt and catch fish.
(a)[2]
State which chemical process is occurring in the seal’s muscles before it dives.
(b(i))[1]
State how much time has passed from the start of the period when the seal starts diving.
(b(ii))[1]
State the percentage of oxygen present in the seal’s blood after 40 minutes from the start of the period.
(c)[3]
Name the chemical process that begins in the seal’s muscles during the dive and explain how the graph provides evidence for your answer.
(d)[3]
Suggest and explain what happens to the concentration of lactic acid in the seal’s blood once it returns to the sea surface after the dive.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “aerobic respiration” …