Ventilation in Insects, Fish and Mammals · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Keeping the gradient steep for every breather

Science · Organisms & Life Processes · ages 16-18
Name ______________________   Date ____________

  1. What drives outside air into your lungs when you breathe in?

    • Your chest expands, pressure inside drops, and air flows high to low
    • Your lungs pull air with tiny hooks
    • Blood sucks the air inward

  2. What does ventilation do at an exchange surface?

    • It refreshes the medium so the gradient stays steep
    • It thickens the exchange surface
    • It shrinks the total surface area

  3. During breathing, air flows from low pressure to high pressure.

    Circle one:   True   False

  4. Why does countercurrent flow outperform parallel flow in gills?

    • It stops blood moving entirely
    • It mixes water and blood together
    • It holds a favourable gradient along the whole plate instead of balancing halfway

  5. Why do huge lungs still need ventilation?

    • Breathing makes the surface even huger
    • Without fresh air the oxygen by the surface runs out and diffusion crawls
    • Ventilation thickens the alveolus walls

  6. How do insects ventilate without lungs?

    • Muscles pump air through tracheal tubes, helped by air sacs
    • They borrow air from nearby plants
    • They hold one breath for life

  7. In gills, blood and water flow opposite so oxygen keeps diffusing in along the whole plate.

    Circle one:   True   False

  8. A student says ventilation makes the exchange surface bigger. What is wrong?

    • Surfaces always shrink during breathing
    • Gradients never matter for diffusion
    • Ventilation refreshes the gradient while the surface stays the same size
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Keeping the gradient steep for every breather W1-mt_Thd06O06Vr-s1

  1. Your chest expands, pressure inside drops, and air flows high to low · Gas follows the pressure difference made by changing chest size.
  2. It refreshes the medium so the gradient stays steep · Fresh air or water keeps the difference between outside and blood steep.
  3. False · Air always runs high to low, filling the gap the chest creates.
  4. It holds a favourable gradient along the whole plate instead of balancing halfway · Head on streams keep every bit of blood beside richer water.
  5. Without fresh air the oxygen by the surface runs out and diffusion crawls · Area without refresh still flattens its own gradient within moments.
  6. Muscles pump air through tracheal tubes, helped by air sacs · Body pumps move air in and out of the tube network directly.
  7. True · Each bit of blood keeps meeting water that carries slightly more oxygen.
  8. Ventilation refreshes the gradient while the surface stays the same size · Ventilation serves the gradient dial, never the area dial.
Worksheet · LightMySky