(a) Describe the process of inhalation in man .
(b) Describe briefly the process of gaseous exchange in the shoo: system of flowering plants.
(c) Describe an experiment to demonstrate the effect of distilled water on mammalian red blood cell.
Explanation
(a)(i) Inhalation involves the contraction of the outer muscles of the diaphragm which makes the diaphragm to pull downward and the intercostal muscles to contract to raise the ribs. The two movements increase the volume of the lungs, thereby reducing the pressure of the air inside them. This enables the air at atmospheric pressure to go into the lungs.
(b) In the shoot system of flowering plants, gaseous exchange takes place through the stomata of the leaves, the green parts and the lenticels at the bark of stem. Stoma is a hole enclosed by two guard cells which change in volume due to osmotic pressure in the guard cells. When the osmotic pressure in the guard cells is high, they become turgid and this makes the stoma to open and when the pressure is low, the guard cells become flaccid and this makes the stoma to close. Generally, exchange of gases in and out of the leaves and lenticels is controlled by the opening and closing of the stomata.
(c) Experiment to demonstrate the effect of distilled water on mammalian red blood cell: Aim: To show that distilled water has effect on the red blood cell.Apparatus: Beaker, distilled water, thistle funnel, ether, pig’s bladder and red blood cells.Method: The pig’s bladder is dissolved in ether to make it soft and used to close or seal the stem end of the thistle funnel. Then pour the red blood cells into the thistle funnel and immerse in water inside the beaker. Mark the initial level of both solutions.Observation and conclusion: It was observed that the level of red blood cells had risen in the thistle funnel indicating that the distilled water moved into the thistle funnel via the pig’s bladder.