Gas Exchange

• What happens to the surface area to volume ratio as the size of an organism increases?

  It decreases
• What does the exchange of substances between an organism and its environment rely on?

  Diffusion
• How do very small organisms meet their gas exchange requirements?

  Through diffusion via their outer surface
• What allows small multicellular organisms to overcome size-related gas exchange problems?

  A flattened shape increases surface area
• Why is there no need for specialized gas exchange organs in small multicellular organisms?

  No cell is far from the surface
• How do small multicellular organisms exchange gases?

  Directly with the environment via diffusion
• What role does a permeable membrane play in gas exchange?

  It allows the diffusion of gases
• How does a moist surface benefit aquatic organisms in gas exchange?

  It allows gases to dissolve and diffuse
• What generates heat in all organisms?

  Metabolic reactions
• What causes increased heat generation during exercise?

  Increased muscle contraction and respiration
• How does a large surface area to volume ratio affect heat loss?

  It allows more skin surface for heat loss
• What is the effect of a small surface area and large volume on heat loss?

  Less skin results in less heat loss
• What are the key features of effective gas exchange surfaces?

  • Large surface area to increase diffusion rate
  • Only 1 or 2 cells thick for short diffusion pathway
  • Thin/flattened cells for efficient gas exchange
  • Extensive blood supply to maintain diffusion gradient
  • Ventilation mechanism to enhance gas exchange
• What is ventilation in the context of human gas exchange?

  Flow of air in and out of lungs
• Which muscles are involved in human breathing?

  Intercostal and diaphragm muscles
• What happens to the diaphragm muscle during inhalation?

  It contracts and flattens
• What occurs during exhalation regarding the diaphragm?

  It relaxes and becomes dome-shaped
• What is the effect of diaphragm relaxation on chest cavity volume?

  It decreases the volume of the chest cavity
• What causes air to flow out of the lungs during exhalation?

  Increased air pressure above atmosphere
• What happens to the diaphragm during inhalation?

  It contracts and moves downwards
• What is the role of external intercostal muscles during inhalation?

  They contract and lift the ribs upwards
• How does inhalation affect the pressure in the thorax?

  It decreases pressure below atmospheric
• What is tidal volume?

  Volume of air breathed in one breath
• How is pulmonary ventilation calculated?

  By multiplying tidal volume and ventilation rate
• What is the formula for pulmonary ventilation?

  Pulmonary ventilation = tidal volume x ventilation rate
• What adaptations do alveoli have for gas exchange?

  Many small alveoli increase surface area
• Why are alveoli made of a single layer of flattened epithelial cells?

  To provide a short diffusion pathway
• How do red blood cells facilitate gas exchange in capillaries?

  They slow down blood flow for more diffusion
• How do insects transport oxygen?

  They do not use blood for oxygen transport
• What are spiracles in insects?

  Paired pores for gas exchange
• What is the function of spiracles in insects?

  Control entry and exit of gases
• What happens when spiracles open in insects?

  Air enters the body
• What is the role of trachea in insect gas exchange?

  They carry oxygen to respiring tissues
• What are tracheoles in insects?

  Smaller tubes branching from trachea
• Where does gas exchange occur in insects?

  At the surface where air tubes meet cells
• How do tracheoles facilitate gas exchange in insects?

  They transport oxygen directly to muscles
• What are the key adaptations of gas exchange in insects?

  • Spiracles control gas entry and exit
  • Trachea transport oxygen to tissues
  • Tracheoles deliver oxygen directly to muscles
  • Tough exoskeleton prevents water loss