SPM Biology 2019


6. (a) Diagram 6.1 shows the structure of human respiratory. Explain how the structure in Diagram 6.1 is adapted to incerease the efficiency of gaseous exchange.

Rajah 6.1 menunjukkan struktur respirasi manusia.Terangkan bagaimana struktur dalam Rajah 6.1 diadaptasi untuk meningkatkan kecekapan pertukaran gas.

Cher Questions Solution Bank Rumusan Jawapan SPM & IGCSE Questions Answers Solution(b) Diagram 6.2 shows two climbers at the peak of Mount Everest on the Himalayas at the height of 8848 metres above sea level. During the climb, the climber encounter breathing difficulty, headache, nausea and dizziness. Explain how their respiratory system is regulated to adapt the situation.

Rajah 6.2 menunjukkan dua orang pendaki di puncak gunung Everest di Banjaran Himalaya dengan ketinggian 8848 meter dari aras laut. Semasa pendakian itu, pendaki mengalami kesukaran bernafas, sakit kepala, loya dan pening. Terangkan bagaimana sistem respirasi mereka dikawal atur untuk menyesuaikan diri dengan situasi itu. Cher Questions Solution Bank Rumusan Jawapan SPM & IGCSE Questions Answers Solution

(c) Diagram 6.3 shows the respiratory system for two organisms, X and Y. Compare and contrast the breathing mechanism for organism X and organism Y.

Rajah 6.3 menunjukkan sistem respirasi bagi dua organisma, X and Y. Banding dan beza mekanisme pernafasan bagi organisma X dan organisma Y. Cher Questions Solution Bank Rumusan Jawapan SPM & IGCSE Questions Answers Solution


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Answer ( 1 )


    a) This structure is called the alveolus. The lungs have a large number of these alveoli thus a large surface area can be provided for efficient gaseous exchange. Next, the wall of the alveolus is only one- cell thick. The thin wall allows for efficient and rapid gas diffusion across the plasma membrane. 


    Other points you could write:
    Furthermore,  there’s a dense network of blood capillaries on the outer surface of the alveoli. This provides a large surface area to volume ratio, allowing for the rapid diffusion of gases from the alveolus to the capillaries. The transport of these gases would be highly efficient as well due to the dense network of capillaries.


    b) The respiratory system will undergo a negative feedback system. The breathing difficulty is most likely due to the increasing blood concentration of carbon dioxide in the body. As the partial pressure of carbon dioxide increases, blood and cerebrospinal fluid (CSF) pH level decreases due to the increasing amounts of carbon dioxide reacting with water which produces carbonic acid.  Central chemoreceptors in the medulla oblongata and peripheral chemoreceptors (aortic and carotid bodies) senses the increasing concentrations of carbon dioxide and drop in blood pH level. These chemoreceptors then send nerve impulses to the respiratory control centre in the brain which then sends signals to the effectors (diaphragm and intercostal muscles) to contract and relax at a quicker rate. Both the breathing and ventilation rate increases, more carbon dioxide gets eliminated from the body. Blood pH level and carbon dioxide concentration then returns to normal levels.



    Organism X Organism Y 
    gaseous exchange occurs via a tracheal system. Air enters through spiracles found along the body of the insect then into the trachea and tracheoles.  gaseous exchange occurs via skin and lungs. Air enters lungs via the glottis. 
    the tips of the tracheoles have thin walls which also contain fluid for respiratory gases to dissolve (efficient diffusion of gases).  lung membranes are very thin and moist to allow for efficient diffusion of gases. 
    Does not require a circulatory system. Organism X has a tracheal system which allows for direct transfer of oxygen from the atmosphere into the body cells.  Does have a network of blood capillaries which allows for transportation of respiratory gases to and from body cells. 
    have numerous tracheoles which allows for a large surface area for efficient gaseous exchange  has numerous inner partitions within the lungs which provides a large surface area for gaseous exchange. 

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