Gaseous Exchange Questions and Answers - Biology Form 2 Topical Revision

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  1. Discuss how gaseous exchange occurs in
    1. Terrestrial Insects (9mks)
    2. Bony fish (11mks)
    1. Explain how mammalian lungs are adapted for gaseous exchange. (8mks)
    2. Describe how carbon dioxide is produced by
      1. Respiring muscle cells reaches the alveolar cavities in mammalian lungs.
      2. Respiring mesophyll cells of flowering plants reaches the atmosphere. (12 mks)
    1. Describe the path taken by carbon dioxide released from the tissues of an insect to the atmosphere.
    2. Name two structures used for gaseous exchange in plants. (2mks)
  4. Why are gills in fish highly vascularized? (1mk)
  5. Describe the
    1. Process of inhalation in mammals. (10 mks)
    2. Mechanism of opening and closing of stomata (10 mks)
  6. Name three sites where gaseous exchange takes place in terrestrial plants. (3mks)
  7. State two ways in which floating leaves of aquatic plants are adapted to gaseous exchange. (2mks)
    1. Name two structures for gaseous exchange in aquatic plants. (2mks)
    2. What is the effect of contraction of the diaphragm muscles during breathing in mammals? (3mks)
  9. The diagram below represents some gaseous exchange structures in humans.
    gaseous exchange in humans
    1. Name the structure labeled K, L and M (3mks)
    2. How is the structure labeled J suited to its functions? (3mks)
    3. Name the process by which inhaled air moves from the structure labeled L into blood capillaries. (1mk)
    4. Give the scientific name of the organism that causes tuberculosis in humans. (1mk)
  10. State three factors that make alveolus adapted to its function. (3mks)
  11. Explain how the alveoli are ventilated.
  12.  Explain why water logging of the soil may lead to death in plants. (2mks)
  13. Write three advantages of breathing through nose than through mouth. (3mks)
  14. State and explain ways the leaves are adapted for gaseous exchange (4mks)
  15. Name three gaseous constituents involved in gaseous exchange in plants. (3mks)
  16. Name three sites of gaseous exchange in frogs. (3mks)
  17.  Name the main site of gaseous exchange in
    1. Mammals
    2. Fish
    3. Leaves
    4. Amoeba (4mks)
  18. Name the physiological process by which gas exchange takes place at the respiratory surface in animals and plants (1mk)
  19. The diagram below represents a part of the rib cage.
    1. Name parts labeled W, Y and Z.
    2. How does the part labeled Z facilitates breathing in? (1mk)
  20. How is aerenchyma tissue adapted to its function? (2mks)


    1. - Air enter into tracheal system through spiracles
      - It moves onto the tracheoles then moves on to the tips of tracheoles.
      - Air rich in oxygen dissolves in a fluid at the tip of the tracheoles. There is low concentration of oxygen in tissues as compared to the fluid.
      - Oxygen diffuses into the tissues due to concentration gradient. It is used in metabolic activities.
      - In tissues there is high carbon dioxide concentration than in the fluid in tracheoles.
      - Carbon dioxide diffuses from tissues into tracheole due to concentration gradient. It moves into trachea then out of the body through spiracles.
    2. - Water enters through the mouth when it opens its mouth. When it closes the floor is raised and water flows over the gills.
      - Oxygen diffuses into the gills blood capillaries while carbon dioxide diffuses from the blood capillaries along concentration gradient.
      - Flow of water and blood in gill filaments is by counter current flow.
    1. - Large number of alveoli-increase surface area.
      - Alveoli moist-dissolve diffusing gases.
      - This walls- allow quick diffusion of gases
      - Rich blood supply- transport oxygen and carbon dioxide.
      1. - Carbon dioxide diffuses into the cells. It moves in the plasma or red blood cells.
        - Carbonic acid in plasma or carbamino haemoglobin in red blood cells or hydrogen carbonate.
        - At the lungs hydrogen carbonate, carbonic acid and carbomino haemoglobin dissociates releasing cavity due to concentration gradient.
      2. - Due to metabolic activities carbon dioxide is released from mesophyll cell. It diffuses into the intercellular spaces.
        - Due to concentration gradient the gas diffuses into the substomatal air spaces.
        - When stomata open carbon dioxide is released into the atmosphere.
    1. Carbon dioxide diffuses into the tracheoles then into the trachea and out into the atmosphere through spiracles.
    2. - Stomata.
      - Lenticels
      - Cuticle
  4. - To facilitate transportation of gases/exchange of gases i.e. oxygen and carbon dioxide.
    - Create high concentration gradient.
    1. - External intercostals muscle contract while internal intercostals muscles relax.
      - Diaphragm contract flattening. Volume in thoracic cavity
      - Air rushes into the lungs.
    2. Opening
      During the day photosynthesis takes place and sugar is formed in 
      guard cells
      - Osmotic pressure increases and water is drawn from neighbouring cells by Osmosis.
      - The guard cells become turgid, bulge outward causing opening of stomata.

      - During the night there is no photosynthesis and sugar is converted 
      to starch.
      - Osmotic pressure decrease and water is lost to the neighbouring cell osmosis.
      - Guard cells become flaccid, closing the stomata.
  6. - Stomata
    - Lenticels
    - Cuticle
  7. - High number of stomata on the upper surface of the leaf.
    - Absence of cuticle to allow diffusion of carbon dioxide and oxygen.
    - The presence of air spaces/aerenchyma tissue which enables them to float.
    1. - Pneumatophores
      - Aerenchyma tissues
      - Cuticle
    2.  - The diaphragm flattens.
      - Volume in thoracic cavity increase.
      - Pressure decreases compared to atmospheric pressure. Air rushes into the lungs through the nostrils.
    1. K- Pleaural membranes
      L - Alveolus
      M- Intercostals muscles
    2.  - Has c-shaped cartilage rings that support it, preventing it from collapsing and allow free flow of air.
      - Inner lining has mucus secreting cells that trap fine dust particles and micro-organisms.
      - Inner lining has hair like structures called cilia that enhance upward movement of the mucus to the larynx.
    3. Diffusion
    4. Mycobacterium tuberculosis
  10. - Highly folded to increase surface area.
    - High network of blood capillaries
    - Thin walled
    - Moist
  11. The trachea are strengthened by rings of cartilage which prevent them from collapsing.
  12. - The epidermis of the root hair cells do not have cuticle and gaseous exchange takes place.
    - When soil is water logged oxygen cannot diffuse into the root tissues hence no respiration. Metabolic activities stop leading to death.
  13. - Air is cleaned by the cilia in nostrils
    - Controlled amount of air is taken in through nose
    - Individual is able to detect the smell of air breathed in.
  14. - Spongy mesophyll cells are loosely packed allowing diffusion of gases.
    - Spongy mesophyll cells have a film of moisture on the surface to dissolve diffusing gases.
    - Large sub-stomatal air space in order to create high concentration gradient of diffusing gases.
    - Presence of stomata where gases enter or leave the leaf.
  15.  - Carbon dioxide
    - Water vapour
    - Oxygen
  16. - Skin
    - Mouth
    1. Mammals –alveoli
    2. Fish – gill filaments
    3. Leaves – spongy mesophyll cells
    4. Amoeba – cells membrane
  18. Diffusion
    1. W - Spinal column
      Y - Sternum
      Z - Intercostal muscles
    2. The external intercostal muscles contracts while the internal intercostal muscles relax this makes he ribcage to move upwards and outwards. The muscles of the diaphragm contracts and it flattens. This increases the volume of the thoracic cavity. The pressure in the thoracic cavity is reduced compared to the surrounding atmospheric pressure and therefore the air is pushed in.
  20. Has air spaces which store gases for gaseous exchange and bouyancy
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