Respiratory system of fish
Although sharks, like all fish, breathe through gills, some need to swim continuously for oxygen-rich water to enter their mouths while others can take in the oxygen they need simply through gulping water and passing it through their gills!
Respiratory system of plants
Plants undergo gaseous exchange through the stomata. In the day, stomata open wide to take in both oxygen (for respiration) and carbon dioxide (for photosynthesis). However, this also means that more water vapour can be lost through the stomata! As a result, they close up in the night when they no longer have to take in carbon dioxide for photosynthesis. This allows them to reduce the amount of water lost.
As its name suggests, gaseous exchange simply involves the exchange of gases! The gases involved are oxygen, which is needed for respiration, and carbon dioxide, which is produced as waste during respiration. The exchange takes place between air in the air sacs, or alveoli, and the bloodstream in the blood vessels surrounding the air sacs.
Breathing refers to the physical process of inhalation, taking in air, and exhalation, expelling air. It involves the collaboration of the respiratory system (lungs), muscular system (diaphragm) and the skeletal system (ribcage)! Observe how these three parts move during inhalation and exhalation to allow air to enter and exit our lungs.