Adaptions of effective gas exchange

• Most animals and plants consist of different types of cells organised as tissues, organs and systems.
• The human respiratory system is a body system adapted for efficient gas exchange.
• In multicellular organisms, surfaces and body organs are specialised for exchanging materials.
• The effectiveness of exchange surfaces in plants and animals is increased by having a large surface area, a short distance required for diffusion, and an efficient blood supply to transport molecules to and from the exchange surface.
• Examples of this include the flattened shape of structures such as leaves, the walls of blood capillaries, and the villi in the small intestine.
• Animals have additional adaptations for effective exchange surfaces.
• Breathing, or ventilation, brings air to, and removes air from the exchange surface – the alveoli.
• The moving blood and ventilated surfaces mean that a steep concentration gradient can be maintained, increasing effective exchange.