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BIOLOGY, M2 EQ-Bank 6

Compare and contrast the microscopic structures involved in gas exchange in mammals and plants.

In your answer, describe one structural similarity between these structures that aids in gas exchange and explain one key difference in how these structures function.   (4 marks)

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→ The primary microscopic structure for gas exchange in mammals is the alveolus, while in plants it is the leaf.
 

Structural similarities that aid in gas exchange (include one):

→ Both have a large surface area to volume ratio to maximise gas exchange.

→ Both have thin, moist surfaces to facilitate the diffusion of gases.
 

Two key differences in how these structures function in gas exchange are:

→ Alveoli primarily exchange oxygen and carbon dioxide with blood, while leaves exchange these gases with air in intercellular spaces.

→ Gas exchange in alveoli occurs continuously for respiration, while in leaves it varies with light availability due to its role in photosynthesis.

Show Worked Solution

→ The primary microscopic structure for gas exchange in mammals is the alveolus, while in plants it is the leaf.
 

Structural similarities that aid in gas exchange (include one):

→ Both have a large surface area to volume ratio to maximise gas exchange.

→ Both have thin, moist surfaces to facilitate the diffusion of gases.
 

Two key differences in how these structures function in gas exchange are:

→ Alveoli primarily exchange oxygen and carbon dioxide with blood, while leaves exchange these gases with air in intercellular spaces.

→ Gas exchange in alveoli occurs continuously for respiration, while in leaves it varies with light availability due to its role in photosynthesis.

BIOLOGY, M2 EQ-Bank 7 MC

Consider the following statements about alveoli in mammals and the internal structure of plant leaves:

\(\text{I.}\)    Both structures have a thin, moist surface to facilitate gas exchange.  
\(\text{II.}\)    Alveoli exchange gases with blood, while leaves exchange gases with air spaces.  
\(\text{III.}\)    Alveoli are specialised for both oxygen uptake and carbon dioxide release,
while leaves are specialised only for oxygen release.		  
\(\text{IV.}\)    Both structures are kept moist to facilitate the diffusion of gases.  

 
Which combination of statements is correct?

  1. \(\text{I}\) and \(\text{II}\) only
  2. \(\text{I, II}\) and \(\text{IV}\) only
  3. \(\text{II, III}\), and \(\text{IV}\) only
  4. \(\text{I, II, III}\) and \(\text{IV}\) only
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\(B\)

Show Worked Solution

Consider each statement.

  • \(\text{I:}\) Correct. Both alveoli and the internal structure of plant leaves have a thin, moist surface to facilitate gas exchange.
  • \(\text{II:}\) Correct. Alveoli exchange gases directly with blood in the surrounding capillaries, while leaves exchange gases with air spaces within their internal structure (intercellular spaces). 
  • \(\text{III:}\) Incorrect. Both alveoli and leaves are specialised for both oxygen uptake and carbon dioxide release.
  • \(\text{IV:}\) Correct. Both structures are kept moist to facilitate the diffusion of gases. 

\(\Rightarrow B\)

BIOLOGY, M2 EQ-Bank 4

Stomata play a crucial role in plant survival.

Explain how environmental factors affect stomatal opening and closing, and discuss the consequences of these changes for the plant.   (3 marks)

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  • Two environmental factors that cause stomata to close are high temperatures and low rainfall (which can often coincide).
  • These environmental factors cause increased water loss from leaves.
  • The closure of the stomata benefits the plant by conserving water, which is crucial for survival in dry conditions.
  • However, a significant drawback is the reduction in CO2 uptake, which limits photosynthesis and can decrease overall plant growth and productivity if prolonged.
Show Worked Solution
  • Two environmental factors that cause stomata to close are high temperatures and low rainfall (which can often coincide).
  • These environmental factors cause increased water loss from leaves.
  • The closure of the stomata benefits the plant by conserving water, which is crucial for survival in dry conditions.
  • However, a significant drawback is the reduction in CO2 uptake, which limits photosynthesis and can decrease overall plant growth and productivity if prolonged.

BIOLOGY, M2 EQ-Bank 6 MC

Which of the following best describes the primary function of stomata in plants?

  1. To absorb water from the atmosphere
  2. To regulate gas exchange and water loss
  3. To produce glucose through photosynthesis
  4. To transport minerals from the roots to the leaves
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\(B\)

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  • Stomata are tiny pores in plant leaves that primarily function to regulate gas exchange.
  • Stomata allow \(\ce{CO2}\) in for photosynthesis and \(\ce{O2}\) out as a byproduct) and control water loss through transpiration. 

\(\Rightarrow B\)

BIOLOGY, M2 2018 HSC 9 MC

Sunken stomata can be found in the leaves of some Australian plants. A section of such a leaf is shown.
 

How do sunken stomata assist the plant to conserve water in a dry environment?

  1. They trap moist air, reducing humidity.
  2. They prevent entry of gases into the leaf.
  3. They accumulate moist air, reducing transpiration.
  4. They increase the surface area available for transpiration.
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\(C\)

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  • A sunken stomata can accumulate moist air between it and the cuticle, hence reducing transpiration and water loss.

\(\Rightarrow C\)