Exchange surface

• What is necessary for an organism to live?

  Constant exchange of substances
• How do unicellular organisms exchange substances?

  Through direct diffusion into and out of the cell
• Why can unicellular organisms exchange substances efficiently?

  They have a large surface area to volume ratio
• What makes substance exchange difficult in multicellular organisms?

  Low surface area to volume ratio
• What do multicellular organisms require for effective substance exchange?

  Specialised exchange surfaces and transport systems
• What are the characteristics of alveoli as a specialized exchange surface?

  • Large surface area
  • Very thin walls
  • Good blood supply
• What is the primary function of alveoli?

  Gas exchange in the lungs
• What happens to oxygen in the alveoli?

  It diffuses into the blood
• What happens to carbon dioxide in the alveoli?

  It diffuses out of the blood
• Why is a good blood supply important for alveoli?

  It allows quick gas exchange
• What are the components of the human circulatory system?

  1. The heart
  2. Blood vessels
  3. Blood
• What type of circulatory system do humans have?

  Double circulatory system
• What occurs in the first circuit of the human circulatory system?

  Blood is pumped to the lungs
• What happens to oxygen in the circulatory system?

  It diffuses into the blood
• What happens in the second circuit of the human circulatory system?

  Blood is pumped to the rest of the body
• What does deoxygenated blood do in the circulatory system?

  Returns to the heart
• What is the advantage of having a double circulatory system?

  Delivers blood at high pressure
• What is the primary function of the heart?

  To pump blood around the body
• What is the role of root hair cells?

  Specialised exchange surface for plants