S.3 Biology Self Study Materials Ncdc Caltec S.3

BIOLOGY SELF -STUDY MATERIALS Senior Three Topic: Gaseous Exchange By the end of this topic, you should be able to demonstrate the mechanism of breathing . Introduction Breathing involves two actions; breathing in (inhalation) and breathing out (exhalation) of air. Activity: Demonstrating breathing In the following activity, you are going to make a model and use it to demonstrate breathing in the human respiratory system. Things you will need : 2 balloons (one small and one large) , straw, empty plastic bottle, rubber band/ string. Set up of the experiment i) Measure 7 cm from the bottom of the water bottle and cut it off. ii) Insert a straw of length 5 cm into the open end of the small balloon. iii) Tie the balloon onto the straw using a rubber band . Mak e sure not to squeeze/ block the straw. iv) Pierce a hole - the size of the straw - on the bottle top (cover of the bottle). v) Insert the remaining open end of the straw through the hole at the bottle cap. Glue / cellotape the straw to make it firm on the cap. vi) Cut the larger balloon in half. Keep the bottom half. vii) Attach the bottom half of the larger balloon firmly around the cut end of the bottle. Procedure Part A 1. What do the following represent? i) Balloon in the bottle ii) Straw iii) Bottle iv) Piece of balloon at the bottom of the bottle 2. Pull the larger balloon at the bottom downwards. i) What does this action represent in the human respiratory system ? ii) Why should the bottom of the balloon be pulled? iii) State what you have observed. iv) Explain your observation. v) What is the equivalent of this action in breathing process? 3. Now release …