exchange surfaces

• how does the size of an organism affect its surface area to volume ratio?

  the larger an organism is the smaller its surface area to volume ratio.
• true or false? single celled organisms with a large surface area to volume ratio can easily exchange substances with the environment, without adaptations.

  true, enough substances can be exchanged across their cell membrane to supply the needs of the cell.
• outline the transport of gases in and out of cells in gas exchange.

  oxygen diffuses into cells and carbon dioxide diffuses out of cells.
• how have exchange surfaces adapted to maximise effectiveness?

  • thin membrane-substances have a short distance to diffuse.
  • large surface-lots of substances can diffuse at once
  • es in animals have lots of blood vessels
  • ges in animals are often ventilated too (air moves in and out)
• how does gas exchange happen in the lungs?

  the lungs contain millions of little air sacs called alveoli where gas exchange takes place.
• how are alveoli specialised to maximise the diffusion of oxygen?

  • an enormous surface surface
  • moist lining for dissolving gases
  • thin walls
  • good blood supply
• name two exchange surfaces in humans.

  alveoli and villi