Gas Exchange in Animals

• Gas exchange in animals is significant as it allows them to obtain oxygen and eliminate carbon dioxide
• Gas exchange facilitates the delivery of oxygen to tissues and ensures the removal of metabolic waste products
• Gas exchange is present in a wide range of animals, from simple unicellular organisms to complex multicellular organisms
• Conditions for efficient gas exchange include:

  • The environment must be moist
  • The membrane must be thin and permeable
  • There must be a large surface area in relation to the volume of the organism
  • There must be a greater concentration of required gas on one side of the membrane than the other
• Organisms will exchange gases with the environment they live in: air or water
• Challenge of multi-cellular organisms on gas exchange: some cells are too far away from the external environment to obtain gases by diffusion
• Animals have specialized structures for efficient gas exchange, with complexity depending on the size, behaviors, and activity levels of the organism
• Air breathers have internal respiratory organs known as lungs
• In air breathers, oxygen is readily available, making them sensitive to changes in carbon dioxide concentration
• The human respiratory system involves the nose, pharynx, trachea, bronchi, bronchioles, and alveoli for gas exchange
• Alveoli provide a large area for gas exchange, lined with a thin layer of flat cells and surfactant to prevent collapse
• Lung ventilation involves the expansion and contraction of the lungs by the diaphragm
• Tidal volume represents the amount of air moved in and out during each breath, while vital capacity is the maximum amount of air that can be moved in one breath
• Residual volume refers to the volume of air left in the lungs after exhalation, preventing lung collapse
• Oxygen is transported in the blood by hemoglobin, forming oxyhemoglobin when bound
• Muscles store oxygen with myoglobin, which has a higher affinity for oxygen than hemoglobin
• Carbon dioxide is carried in the blood as carbaminohaemoglobin or converted into hydrogen carbonate ions
• Ventilation in air breathers is controlled by carbon dioxide levels in the blood
• Gills in aquatic animals rely on water buoyancy to prevent collapse and require water movement for gas exchange
• Countercurrent flow in gills allows for efficient extraction of oxygen from water
• Ventilation in aquatic animals is regulated by oxygen levels in the blood