I am not sure because there may be more context, but here is what I am guessing the answer is.
As Bryson pedaled uphill both his heartbeat and breathing rate increased. His breathing rate increases to provide the body (more specifically, exercising muscles) with oxygen at a higher rate and his heart rate increases to deliver the oxygen (and glucose) to the respiring muscles more efficiently.
Turtles can either breath through their back end or through their mouth if they choose to.
Broken down by the acids in your stomach
The biosphere is everything. the whole planet. so all of the above is right
