Exchange Surfaces

• What is the main focus of the section on exchange surfaces in multicellular organisms?

  How substances move through them effectively
• What are the adaptations of exchange surfaces in multicellular organisms to maximize effectiveness?

  • They are thin for short distance travel
  • They have a large surface area for increased substance movement
  • They contain many blood vessels for quick substance exchange
  • They are positioned to facilitate air movement in gas exchange surfaces
• Why are exchange surfaces in multicellular organisms thin?

  To ensure substances have a short distance to travel
• What is the purpose of having a large surface area in exchange surfaces?

  To allow lots of substances to move at once
• How do blood vessels contribute to the effectiveness of exchange surfaces in animals?

  They help get substances in and out of the blood quickly
• Where does gas exchange occur in mammals?

  In the lungs
• What is the primary function of the lungs?

  To transfer oxygen to the blood and remove carbon dioxide
• What are the tiny air sacs in the lungs called?

  Alveoli
• How do alveoli maximize the diffusion of gases?

  They have a large surface area, moist lining, thin walls, and a good blood supply
• What is the approximate surface area of alveoli in humans?

  About 75 m²
• What happens to carbon dioxide in the lungs during gas exchange?

  It diffuses out of the blood into the alveoli
• What happens to oxygen during gas exchange in the lungs?

  It diffuses from the alveolus into the blood
• What is the role of the small intestine in the digestive system?

  To absorb dissolved food molecules into the blood
• What are the tiny projections in the small intestine called?

  Villi
• How do villi enhance the absorption of food molecules?

  They increase the surface area for quicker absorption
• What features do villi have to assist in absorption?

  They have a single layer of surface cells and a good blood supply
• Why is it beneficial for an exchange surface to be just one cell thick?

  It minimizes the distance for diffusion, enhancing efficiency
• What is the primary function of leaves in plants?

  To facilitate efficient gas exchange
• How are leaves adapted to maximize the diffusion of O₂ and CO₂?

  Leaves have a large surface area, thin structure, and stomata for gas exchange
• What is the role of root hairs in plants?

  To absorb water and mineral ions from the soil
• How are plant roots adapted to absorb lots of water and mineral ions?

  Roots have a large surface area and root hairs to increase absorption efficiency
• What are the adaptations of leaves for gas exchange?

  • Large surface area
  • Thin structure for short diffusion distance
  • Presence of stomata for gas exchange
• What are the adaptations of roots for water and mineral ion absorption?

  • Large surface area due to root hairs
  • Thin cell walls for easier absorption
  • Proximity to soil moisture and nutrients
• What is the significance of the phrase "Thirsty? Go dip your hair in your drink..." in relation to root hairs?

  It suggests that root hairs absorb water like hair absorbs liquid
• Why is a large surface area important for leaves and roots?

  A large surface area increases the efficiency of gas exchange and absorption
• If a plant has small leaves, how might this affect its gas exchange efficiency?

  It would likely reduce the efficiency of gas exchange
• What is the role of stomata in leaves?

  Stomata allow for the exchange of gases like O₂ and CO₂
• How many marks are allocated for explaining how leaves are specialized for gas exchange?

  3 marks
• How many marks are allocated for explaining how plant roots absorb water and mineral ions?

  2 marks
• What is the importance of gas exchange in plants?

  • Essential for photosynthesis
  • Provides O₂ for respiration
  • Removes excess CO₂