Intro

• What is the importance of surface area to volume ratio in organisms?

  It affects the efficiency of exchange processes
• How does the size of an organism affect its surface area to volume ratio?

  As size increases, the ratio decreases
• How would you calculate the surface area to volume ratio for a cell with a radius of 1µm?

  Use the formula: SA:Vol = Surface area / Volume
• What does Fick's Law state about the rate of diffusion?

  It is proportional to surface area and concentration gradient
• What are the key components of Fick's Law?

  • Surface area
  • Concentration gradient
  • Length of diffusion pathway
• What shape is useful for modeling cells or organisms?

  A sphere
• How do you calculate the surface area and volume for a sphere?

  • Surface area: $4\pi r^2$
  • Volume: $\frac{4}{3}\pi r^3$
• What is the surface area to volume ratio for a cell with a radius of 1µm?

  3:1
• What is the surface area to volume ratio for a cell with a radius of 3µm?

  1:1
• What is the surface area to volume ratio for a cell with a radius of 5µm?

  0.75:1
• Why do single-celled organisms not need specialized exchange surfaces?

  • They are small
  • High surface area to volume ratio
  • Gases can easily exchange across body surface
• What are the main features of efficient exchange surfaces?

  • Large surface area
  • Thin layers
  • Selectively permeable
  • Transport system for internal medium
• How do the SA:Vol ratios of organisms with different radii compare?

  Smaller organisms have higher SA:Vol ratios
• Why do larger organisms need specialized exchange surfaces?

  They have a low surface area to volume ratio
• What is one reason multicellular organisms need specialized exchange systems?

  Some cells are deep within the body
• What features have evolved in multicellular organisms for exchange?

  • Flattened shape
  • Specialised exchange surfaces
  • Mass transport systems
• What is a waste product from the breakdown of amino acids?

  Urea
• What substances need to be exchanged between organisms and their environment?

  Oxygen, carbon dioxide, water, nutrients, urea, heat
• What are the features of specialized exchange surfaces in multicellular organisms?

  1. Large surface area to volume ratio
  2. Thin layers for rapid diffusion
  3. Transport systems for internal medium
  4. Movement of environmental medium
• What is the role of the skin in exchange processes?

  It acts as a barrier and regulates exchange
• Why is diffusion too slow for multicellular organisms?

  They would not survive without specialized systems
• How does the complexity of organisms relate to their exchange systems?

  • More complex organisms have lower SA:Vol ratios
  • They require specialized exchange surfaces
  • They have higher metabolic rates