exchange surfaces

• small organism like flatworms can exchange substances through their body surface through diffusion, larger organisms need a circulatory system
• example : villi cover small intestine wall increasing surface area so more nutrients can be absorbed into the blood
• alveoli

  function substances exchanged adaptations

  put oxygen air very thin alveolus

  in and CO2 out walls, spherical

  shape
• villi

  function substances exchanged adaptations

  absorb nutrients glucose diffuses into very thin walls

  blood stream increase sa

  of small intestine
• leaf

  function substances exchanged adaptations

  photosynthesis take in CO2 and release green, lots of

  oxygen produced chlorophyll to

  absorb sunlight

  large SA, moist

  cells