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. Which sequence explains airflow into mammalian lungs during inhalation?

    • Lungs expand, lung pressure falls, and air enters
    • Lungs expand, lung pressure rises, and air enters
    • Lungs contract, lung pressure falls, and air enters

  2. What is ventilation's main contribution to gas exchange?

    • Renewing air or water to maintain gas gradients
    • Making every exchange barrier thicker during use
    • Reducing the exchange area available to both gases

  3. During quiet exhalation, air leaves because lung pressure is lower than atmospheric pressure.

    Circle one:   True   False

  4. Why can countercurrent flow extract more oxygen than parallel flow in an otherwise comparable fish-gill model?

    • It keeps blood still while water moves along the lamella
    • It lets water and blood mix directly inside the lamella
    • It maintains an uptake gradient along the lamella

  5. Why do lungs with a large exchange area still need ventilation?

    • A large area prevents gases crossing until air is renewed
    • Without renewal, gas gradients fall as exchange proceeds
    • A large area makes barrier thickness increase unless air moves

  6. How can many active insects increase airflow through their tracheal system?

    • Body movements create pressure changes that move air
    • Blood pumps air through every branching tracheal tube
    • Open spiracles drive bulk airflow even when pressures are equal

  7. At one point on a gill lamella, water has oxygen partial pressure 6 and adjacent blood has 4, in matching units. This local gradient favours oxygen entering blood.

    Circle one:   True   False

  8. At a breathing pause with open airways, lung and atmospheric total pressures are equal. Oxygen partial pressure is still higher in alveolar air than in blood. A student says both airflow and oxygen diffusion must stop. Which correction fits?

    • Both continue because the oxygen gradient also drives bulk airflow
    • Both stop because equal total pressures remove every gas gradient
    • Bulk airflow stops; oxygen can still diffuse into blood
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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. Lungs expand, lung pressure falls, and air enters · Expansion lowers lung pressure below atmospheric pressure. Air then flows into the lungs.
  2. Renewing air or water to maintain gas gradients · Renewing the medium helps maintain gradients as oxygen enters the animal and carbon dioxide leaves it.
  3. False · During outward airflow, lung pressure is above atmospheric pressure. Air flows from higher to lower total pressure.
  4. It maintains an uptake gradient along the lamella · Opposite flows maintain favourable local oxygen partial-pressure differences. In parallel flow, the partial pressures approach each other and the gradient declines.
  5. Without renewal, gas gradients fall as exchange proceeds · Area alone cannot maintain gradients. Oxygen uptake and carbon dioxide release alter nearby air unless it is renewed.
  6. Body movements create pressure changes that move air · Body movements compress and expand parts of the tracheal system, producing pressure differences. Open spiracles permit airflow but do not drive it when pressures are equal.
  7. True · Water has higher oxygen partial pressure than adjacent blood, so net oxygen diffusion at this point is into blood.
  8. Bulk airflow stops; oxygen can still diffuse into blood · Equal total pressures remove the driving difference for bulk airflow. The stated oxygen partial-pressure difference still favours diffusion into blood.
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