Science 8 · Unit 1: Respiration · Cambridge Lower Secondary Science Stage 8

Questions

1. 1. Where does gas exchange happen in the lungs?

   • in the trachea
   • in the diaphragm
   • in the air sacs (alveoli)
   • in the larynx
   Check

2. 2. Which gas moves from the air sacs into the blood?

   • carbon dioxide
   • oxygen
   • water vapour only
   • nitrogen
   Check

3. 3. Which gas moves from the blood into the air sacs?

   • helium
   • carbon dioxide
   • oxygen
   • nitrogen
   Check

4. 4. How do gases move between the air sacs and the blood?

   • by pumping
   • by filtering
   • by diffusion
   • by evaporation
   Check

5. 5. Why do air sacs have very thin walls?

   • so they make sound
   • so gases can diffuse through quickly
   • so they are strong
   • so they hold more blood
   Check

6. 6. Why do lungs have millions of air sacs?

   • to store food
   • to make the lungs heavy
   • to give a very large surface area for gas exchange
   • to make the lungs smaller
   Check

7. 7. Why are air sacs surrounded by many capillaries?

   • to stop gas exchange
   • to keep them warm only
   • to make them stronger
   • to carry oxygen away and bring carbon dioxide quickly
   Check

8. 8. Human 80 000 g / 70 m², sheep 68 000 g / 60 m², mouse 20 g / 0.1 m². What is the pattern?

   • All animals have the same area.
   • The larger the body mass, the larger the air sac surface area.
   • There is no pattern.
   • Smaller animals have larger surface areas.
   Check

9. 9. Why do larger mammals need a larger air sac surface area?

   • They need less oxygen.
   • They have smaller lungs.
   • They have more cells that need oxygen.
   • They breathe more slowly.
   Check

10. 10. What is a correlation?

    • a kind of graph paper
    • an experiment with no results
    • a type of cell
    • a relationship between two variables
    Check

11. 11. The table lists the mammals in no particular order. Why would it help to put them in order of body mass?

    • It isn't helpful.
    • It makes the table shorter.
    • It makes the pattern easier to see.
    • It changes the results.
    Check

12. 12. What is the moist lining of the air sacs for?

    • It stops diffusion.
    • It traps food.
    • Gases dissolve in it before diffusing.
    • It makes the sacs heavier.
    Check

13. 13. Blood arriving at the lungs is low in which gas?

    • oxygen
    • carbon dioxide
    • nitrogen
    • water
    Check

14. 14. Look at the table. Which mammal has the smallest air sac surface area?

    • the rabbit
    • the mouse
    • the rat
    • the fox
    Check

15. 15. Look at the table. Which mammal has the largest air sac surface area?

    • the rabbit
    • the sheep
    • the fox
    • the human
    Check

16. 16. Which gas turns limewater cloudy?

    • carbon dioxide
    • nitrogen
    • water vapour
    • oxygen
    Check

17. 17. Expired air and inspired air are bubbled through limewater. Which makes it go cloudy first, and why?

    • expired air, as it has more oxygen
    • inspired air, as it has more carbon dioxide
    • expired air, as it has more carbon dioxide
    • inspired air, as it has less oxygen
    Check