2.1 Need for gas exchange surfaces

Why do we need gas exchange systems to be efficient?

• supply O2 for respiration

• remove waste CO2 from respiration

• Gas exchange occurs by diffusion

Why do larger organisms need specialised gas exchange surfaces?

• smaller SA:V ratio

• greater demand for oxygen

• longer diffusion distances

Why can't diffusion alone meet the demands of large organisms?

• A low SA:V ratio.

• A high total demand for oxygen because they have many respiring cells.

• Cells deep inside the body, creating long diffusion distances.

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