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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.
→ 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.
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?
\(B\)
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.
\(\Rightarrow B\)
Explain how the respiratory structures of a terrestrial mammal and a bony fish are adapted to their respective environments.
In your answer, discuss how the structure of each system maximises gas exchange. (4 marks)
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→ The main respiratory organ in terrestrial mammals is the lungs, while in bony fish it’s the gills.
→ Lungs have a large internal surface area created by millions of alveoli.
→ This highly efficient structure, combined with the diaphragm-driven breathing mechanism, allows for rapid oxygen uptake and carbon dioxide release. This ensures that all cells receive adequate gas exchange despite the lower oxygen content in air compared to water.
→ Gills consist of many thin filaments that spread out in the water to provide a large surface area for gas exchange.
→ Fish are able to take in water through their mouths and force the water over their gills. This creates a consistent one-way flow of oxygen-rich water for gas exchange.
→ Fish use a counter-current flow in their gills to maximise oxygen uptake, which is not necessary in lungs.
→ The main respiratory organ in terrestrial mammals is the lungs, while in bony fish it’s the gills.
→ Lungs have a large internal surface area created by millions of alveoli.
→ This highly efficient structure, combined with the diaphragm-driven breathing mechanism, allows for rapid oxygen uptake and carbon dioxide release. This ensures that all cells receive adequate gas exchange despite the lower oxygen content in air compared to water.
→ Gills consist of many thin filaments that spread out in the water to provide a large surface area for gas exchange.
→ Fish are able to take in water through their mouths and force the water over their gills. This creates a consistent one-way flow of oxygen-rich water for gas exchange.
→ Fish use a counter-current flow in their gills to maximise oxygen uptake, which is not necessary in lungs.
Explain how the structure of the alveoli is suited to their function of gas exchange. (3 marks)
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→ Alveoli are the millions of microscopic air sacs which are in mammalian lungs.
→ They are surrounded by capillaries which contain deoxygenated blood. When air is inhaled the oxygen is able to diffuse into the blood along its concentration gradient.
→ The miniature size of alveoli is what allows simple diffusion to occur, while their abundance in mammalian lungs maximises the surface area, allowing more frequent gas exchange.
→ Alveoli are the millions of microscopic air sacs which are in mammalian lungs.
→ They are surrounded by capillaries which contain deoxygenated blood. When air is inhaled the oxygen is able to diffuse into the blood along its concentration gradient.
→ The miniature size of alveoli is what allows simple diffusion to occur, while their abundance in mammalian lungs maximises the surface area, allowing more frequent gas exchange.