Oxygen is used up in the body of most organisms and Carbon dioxide is released. The body uses oxygen to break down glucose to supply energy tot he body. In result of this reaction carbon dioxide and water is released into the system along with energy. The carbon dioxide is then exhaled into the air by the respiratory system of the organisms.
The above is not an example of sexual selection because sexual selection is about differential success in acquiring males.In sexual selection one biological sex chose mates of other sex to mate with. and compete with members of the same sex for access of members of opposite sex
