When they breathe out. Also after they die, during decomposition.
Plants take in carbon dioxide and give off oxygen Animals take in oxygen and give off carbon dioxide
Carbon dioxide
carbon dioxide
carbon dioxide
Plants must have carbon dioxide from animals. Animals give off carbon dioxide when they breathe and plants give off oxygen so it's a fair exchange.
Methane and carbon dioxide.
respiration
CaRbon dioxide.
Oxygen is actually breathed in by animals. It is carbon dioxide which is exhaled by animals. Plants take in carbon dioxide and give off oxygen.
Animals give off CO2 [carbon dioxide] and they reward us with O2 [oxygen].
Respiration
carbon dioxide gas