Exchange of materials

• What do all organisms need to survive?

  To exchange materials with their environment
• Why do organisms need to exchange substances with their environment?

  To take in necessary substances and eliminate waste
• What substances do organisms take in from the environment?

  • Oxygen
  • Water
  • Carbon dioxide
  • Food
  • Mineral ions
• What waste products do organisms get rid of?

  • Carbon dioxide (from aerobic respiration)
  • Urea (from protein breakdown in animals)
• How are substances exchanged in organisms?

  By diffusion, osmosis, and active transport
• What affects the rate of substance exchange in organisms?

  The surface area to volume ratio
• What does a surface area to volume ratio indicate?

  • Comparison of a shape's surface size to its volume
• How do you calculate the surface area of a rectangle?

  Length x Width
• What is the surface area of a 4 cm x 4 cm block's top and bottom surfaces?

  32 cm²
• How do you calculate the volume of a block?

  Length x Width x Height
• What is the volume of a block measuring 4 cm x 4 cm x 2 cm?

  32 cm³
• What is the surface area to volume ratio of the hippo?

  2 : 1
• How does the size of an organism affect its surface area to volume ratio?

  Larger organisms have smaller ratios
• Compare the surface area to volume ratios of a hippo and a mouse.

  • Hippo: 2 : 1
  • Mouse: 6 : 1
  • Mouse has a larger surface area compared to its volume
• What happens when an organism has a smaller surface area compared to its volume?

  It is harder to exchange substances
• What is the surface area to volume ratio of a cube with sides measuring 5 cm?

  6 : 5
• How can you calculate the surface area to volume ratio of a cube?

  1. Calculate surface area: 6 x (side length)^2
  2. Calculate volume: (side length)^3
  3. Ratio: Surface Area : Volume