B3.1: Gas Exchange

Which one of the following statements is true of transpiration?

• With higher humidity rate increases

• With greater wind speed rate decreases

• With greater light intensity rate increases

• With lower temperatures rate increases

How is the concentration gradient of water maintained in the leaf?

I.Stomata opens to allow water vapour to escape.

II.Air spaces in the spongy mesophyll allow water from the mesophyll cells to evaporate.

III.Waxy cuticle layer of the upper epidermis reduces the amount of water escaping the leaf.

• I only

• III only

• I and II only

• I, II and III

Which method(s) could be used to measure ventilation rate?

I.Strap a belt around the chest and measure the pressure from the contraction and expansion of the chest using a data logger.

II.Breathe into a mouthpiece connected to a spirometer and measure the volume of air inhaled and exhaled over a period of time.

III.Place hands on the chest and count the number of times the chest rises over a period of time.

• I only

• III only

• I and II only

• I, II and III

The alveoli are the site of gas exchange in the lungs. Which is not a way that the concentration gradient of oxygen is maintained across the alveoli?

• A dense network of capillaries surrounding the alveoli

• Thin-walled alveoli

• Continuous blood flow

• Ventilation from the air

Which of the following takes place during exhalation?

I. The diaphragm forms a dome shape

II. Internal intercostal muscles contract

III. Pressure increases inside the lungs

• I only

• II only

• I and III only

• I, II and III