Topic 3

• What topics are covered in these notes?

  Surface area to volume ratio, gas exchange, digestion
• How do thin, flat, folded, or elongated structures affect the SA:V ratio?

  They increase SA:V
• What happens to the SA:V ratio as size increases?

  SA:V tends to decrease
• How do you calculate SA:V?

  Divide surface area by volume
• How do you calculate surface area?

  Size length x side width x number of sides
• How do you calculate volume?

  Length x width x depth
• What is a reason for calculating SA:mass instead of SA:V?

  Easier to find because irregular shapes
• What is the definition of metabolic rate?

  Energy used by an organism within a time
• How is metabolic rate often measured?

  By oxygen uptake
• Why is oxygen uptake used to measure metabolic rate?

  Used in aerobic respiration to make ATP
• Why does metabolic rate increase as SA:V increases?

  Rate of heat loss per unit mass increases
• What do organisms with higher SA:V need to do to maintain body temperature?

  Higher rate of respiration
• Why do smaller organisms need a higher rate of respiration?

  To release enough heat to maintain temperature
• How do changes to body shape facilitate exchange as SA:V reduces?

  Increases SA:V and reduces diffusion distance
• How do specialized surfaces maintain a concentration gradient?

  By ventilation or good blood supply
• What happens to the rate that volume increases compared to surface area, as size increases?

  Volume increases faster than surface area
• Why is it incorrect to say "Respiration produces energy"?

  Energy can only be released
• How is a single-celled organism's body surface adapted for gas exchange?

  Thin shape and large SA:V ratio
• Why is a short diffusion distance important for gas exchange in single-celled organisms?

  Rapid diffusion of gases
• What are the key components of an insect's tracheal system?

  • Spiracles: pores on surface
  • Tracheae: large tubes full of air
  • Tracheoles: smaller branches from tracheae

  
• What is the function of tracheoles in the insect tracheal system?

  Gas exchange with cells

  
• How do tracheoles facilitate gas exchange in insects?

  Short diffusion distance to cells
• Why is having high numbers of highly branched tracheoles an adaptation for gas exchange in insects?

  Large surface area and short distance
• How do tracheae facilitate gas exchange in insects?

  Provide tubes full of air

  
• How does abdominal pumping aid gas exchange in insects?

  Maintains concentration gradient for diffusion
• What causes fluid to be drawn into tissues from tracheoles during exercise in insects?

  Lactate produced in anaerobic respiration lowers ψ
• How does the movement of fluid from tracheoles affect gas exchange?

  Rate of diffusion increases
• How does the thick waxy cuticle of insects limit water loss?

  Increases diffusion distance
• How do spiracles in insects help to limit water loss?

  They can close to reduce evaporation
• How do hairs around spiracles reduce water loss?

  Trap moist air, reducing ψ gradient
• How do filaments and lamellae contribute to gas exchange in fish gills?

  Increase surface area for diffusion
• How does the thin epithelium of lamellae aid gas exchange?

  Short diffusion distance
• How do capillaries in lamellae maintain a concentration gradient?

  Remove O2 and bring CO2 quickly
• What is the function of countercurrent flow in fish gills?

  Maintains concentration gradient of O2
• Why is countercurrent flow more efficient than parallel flow?

  Maintains diffusion along whole length of lamellae
• What would happen in fish gills if blood and water flowed in parallel?

  Equilibrium would be reached
• How do stomata contribute to gas exchange in dicotyledonous plant leaves?

  Large surface area for gas exchange
• What is the role of spongy mesophyll in gas exchange in leaves?

  Large surface area for gases to diffuse
• How does leaf thinness aid gas exchange?

  Short diffusion distance
• What is a xerophyte?

  Plant adapted to live in dry conditions