Compare and contrast mammals and fish breathing?

Mammals breathe air using lungs, extracting oxygen from the atmosphere through inhalation and expelling carbon dioxide during exhalation. In contrast, fish breathe underwater using gills, which absorb oxygen dissolved in water as it flows over them. While both systems are designed for gas exchange, mammals rely on a diaphragm and rib cage to facilitate lung expansion, whereas fish use the movement of water to ensure oxygen flow over their gills. Additionally, mammals are generally adapted for a terrestrial environment, while fish are specialized for aquatic living.