Gas exchange

• What is the primary function of gas exchange organs?

  To facilitate the exchange of gases necessary for respiration and photosynthesis
• What are the two major adaptations of gas exchange surfaces?

  • Large surface area
  • Thin layer of epithelial cells for a short diffusion pathway
• How do the adaptations of gas exchange surfaces increase the rate of diffusion?

  By providing a larger area and a shorter distance for gases to diffuse
• What do single-celled organisms use for gas exchange?

  They absorb and release gases by diffusion through their outer surface
• What characteristics do single-celled organisms have that facilitate gas exchange?

  They have a relatively large surface area, a thin surface, and a short diffusion pathway
• Why do fish have special adaptations for gas exchange?

  Because there is a lower concentration of oxygen in water than in air
• Describe the process of gas exchange in fish.

  1. Water enters the fish through the mouth and passes out through the gills.
  2. Gills are made of thin plates called gill lamellae, providing a large surface area.
  3. Lamellae are covered in capillaries and have a thin surface layer for efficient diffusion.
• What is a counter-current system in fish gills?

  It is when blood flows through the lamellae in one direction and water flows over in the opposite direction
• How does the counter-current system benefit fish?

  It maintains a large concentration gradient between the water and the blood
• What are tracheae in insects?

  Microscopic air-filled pipes used for gas exchange
• How do insects exchange gases using tracheae?

  1. Air enters through pores called spiracles.
  2. Tracheae branch into smaller tracheoles that reach individual cells.
  3. Oxygen diffuses directly to cells, and carbon dioxide moves towards spiracles to be released.
• What role do spiracles play in gas exchange for insects?

  They are the openings through which air enters and exits the tracheae
• How do insects minimize water loss during gas exchange?

  By closing their spiracles and having a waterproof cuticle
• What adaptations do dicotyledonous plants have for gas exchange?

  • Large surface area of mesophyll cells
  • Gas exchange occurs through stomata in the epidermis
  • Stomata can open and close to regulate water loss
• What is the function of guard cells in plants?

  They control the opening and closing of stomata
• How do plants adapt to minimize water loss during gas exchange?

  By closing stomata when dehydrated and having a waxy cuticle
• What are some adaptations of xerophytic plants for water conservation?

  • Stomata sunk in pits to trap moist air
  • Layer of hairs on the epidermis to reduce evaporation
  • Curled leaves to protect stomata from wind
  • Reduced number of stomata
  • Waxy, waterproof cuticles
• What is the main gas exchange surface in dicotyledonous plants?

  The surface of the mesophyll cells in the leaf
• Why do plants need both oxygen and carbon dioxide?

  Oxygen is needed for respiration, and carbon dioxide is needed for photosynthesis
• How do the adaptations of gas exchange organs in different organisms compare?

  They all aim to maximize surface area and minimize diffusion distance
• What is the trade-off that occurs during gas exchange?

  Exchanging gases tends to lead to water loss
• What happens to guard cells when a plant starts to dehydrate?

  They lose water and become flaccid, closing the stomatal pore
• What is the role of the mesophyll cells in plants?

  They are the main site for gas exchange in leaves
• How do curled leaves help xerophytic plants?

  They protect stomata from wind, reducing evaporation
• What is the significance of having a large surface area in gas exchange organs?

  It allows for more efficient gas exchange
• How do the adaptations of gas exchange systems in insects differ from those in plants?

  Insects use tracheae for direct gas exchange, while plants use stomata
• What is the primary waste gas produced by respiration in plants?

  Carbon dioxide
• Why do plants need to open their stomata during the day?

  To allow for gas exchange necessary for photosynthesis
• What happens to the concentration gradient of water when stomata are sunk in pits?

  It reduces the concentration gradient, minimizing water loss
• What is the function of the cuticle in plants?

  To reduce evaporation of water
• How do tiny hairs around the spiracles help insects?

  They reduce evaporation by trapping moisture
• What is the role of abdominal movements in insects regarding gas exchange?

  They help move air in and out of the spiracles