IB Biology Practical Investigations/Human Health and Physiology/Model Digestive System

MODELLING THE DIGESTIVE SYSTEM
TEACHING OBJECTIVE:
 * To demonstrate and explain the basic steps in digestion

TASK OUTCOMES:
 * By the end of this activity, students will be able to explain what happens to food as it makes the journey from the mouth to the anus.

TIME REQUIRED:
 * 20 minutes if teacher-led, 1hr if student-led

INTRODUCTION: Digestion is simple, gooey and visual with this demonstration activity. The teacher can use the image to build a model digestive system to explain the steps 'from food to poo'. Alternatively, the teacher can provide the students with the materials needed and set them the task of preparing, practising and presenting the stages of digestion to an audience. In the canteen at lunch time would be a good crowd-pleaser!

MATERIALS AND EQUIPMENT: (per model produced)


 * plastic funnel


 * long balloon, end cut off


 * rubber glove, one finger chopped


 * 30cm hose


 * one leg of pantyhose


 * large beaker/ bucket


 * duct tape, scissors


 * 5 sandwich-bag clips or strong clothes pegs


 * some (brown) cereal, milk, juice and a spoon

OTHER RESOURCES NEEDED:


 * Texbook/study guide

INSTRUCTIONS:


 * TRY IT OUT BEFORE THE LESSON!


 * Having made the model, use it to demonstrate the stages of digestion, beginning with chewing in the mouth (smash up the cereal and juice with a spoon), through to defaecation (squueze out the stool into a beaker).


 * Along the way, use as much detail as relevant to the audience. For DP students, actions at each stage and enzymes used will be beneficial. If students are modelling to younger students, keep it simple and fill the blanks in class.



SAFETY/ RISK ASSESSMENT


 * Clean up thoroughly


 * Do not eat the food (though for an added 'eugh!' factor, you might want to dip younger finger in the 'stool' and taste it)!


 * Be careful of food allergies

IDEAS FOR FURTHER INVESTIGATION


 * Video the presentations


 * flow-chart the digestive process, including enzymes at each stage



SOURCES AND REFERENCES: