Exchange surfaces

• What makes it easier for an organism to exchange substances with its environment?

  The surface area to volume ratio
• How do you find surface area?

  Length x width
• How do you find the volume?

  Length x width x height
• Why can single-celled organisms diffuse substances directly into the cell?

  Large surface area compared to their volume
• Why can gases and dissolved substances diffuse directly into or out of the cell in single-celled organisms?

  They have a large surface area
• What do multicellular organisms need in order for substances to diffuse?

  An exchange surface
• How are exchange surfaces adapted?

  They have a thin membrane, a large surface area and lots of blood vessels in animals