Food and digestion. Background. Suggested teaching sequence. A pupil working at:

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1 1 of 5 Food and digestion Background A pupil working at: Level 4 can use scientific names for the main organs of the digestive system and can accurately locate them; can use scientific names for food groups. Level 5 can describe the functions of the main organs of the digestive system; can describe the functions of the major food groups, name foods that are rich in them and know the principles of a balanced diet. To move pupils from level 4 to level 5 1. Introduce key organs of the digestive system on a model or a picture. 2. Use modelling to describe what happens to food during the digestion process. 3. Introduce key words for food groups. 4. Introduce sources of food groups and their functions through secondary sources. 5. Familiarise pupils with the concept of a balanced diet. Suggested teaching sequence The following activities could all be done in one lesson or split into separate activities and spread over more than one lesson. 1. To identify and locate the main organs of the digestive system Organise pupils into groups of two or three. Each group is given a diagram of the human digestive system with no labels, copied onto an A4 sheet of paper. Provide (either on the board or as a set of cards for each group) the following labels: mouth food pipe (oesophagus) stomach small intestine large intestine

2 Mini 2 of 5 rectum anus Give pupils access to secondary sources such as textbooks if they are stuck. Allow 2 3 minutes for pupils to place the labels in the correct position on the diagram. Ask pupils to indicate when they have finished. Their work is then checked for accuracy. The group that completes the labelling the fastest wins. If pupils are uncertain or unable to complete the task in the required time, repeat the exercise at the end of the teaching sequence to check for improved knowledge. 2. To model the physical changes in food as it passes through the digestive system and to reinforce the knowledge and understanding of some of the functions of the organs This activity is a teacher demonstration and is intended to be used as a review of pupils knowledge and understanding of the digestive system. It is important that during the demonstration the teacher checks the pupils appreciation of what the components represent and the limitations of the model. Some questions are provided as prompts. Questions in italics are to be used if the purpose of the demonstration is to review chemical as well as physical digestion. Stress that this model is representing only the physical changes to food as it passes through the gut. To discuss chemical changes pupils will need to be familiar with digestive enzymes their location and function. Grind up some weetabix or similar cereal with water using a pestle and mortar to form a pourable paste. What do the pestle and mortar represent? What does the water represent? What enzyme is present here and what does it do? Pour the mixture through a funnel attached to a tube that leads to a polythene bag. What do the tube and polythene bag represent? Squeeze the bag to mix the contents. What enzyme is present here and what does it do? What else is added to the food here and what does it do? Pour the slurry into a nylon stocking (or half a pair of tights) with a constriction half way down (this can be made by tying string or an elastic band around the stocking).

3 3 of 5 What do the two parts of the stocking represent? What enzymes are present here and what do they do? Squeeze the top of the stocking to represent peristaltic movement. Allow some of the slurry to come out of the stocking through the nylon. What does the semi-liquid that oozes out of the stocking represent? What enzymes are present here and what do they do? Open the constriction and squeeze the contents into the lower half of the stocking. This time squeeze as much of the liquid out of the stocking as possible. What does this represent as happening in the large intestine? Push the remains into the foot of the stocking. Cut the end off the stocking and squeeze out the semi-dry lump. What process does this represent and what does the lump of weetabix represent? Summarise on the board the parts of the model and what they represent. Divide pupils into groups of two or three. Assign each group a part of the model and the organ it represents. Give pupils 5 minutes to find as many examples as possible that show the model is a good representation and also to highlight any weaknesses. Take feedback and then give each group another 5 minutes to suggest at least one improvement to the model for the organ they have been assigned. 3. To reinforce pupils understanding of the key words mouth, oesophagus (food tube), stomach, small intestine, large intestine, rectum and anus Ask pupils, in pairs, to write dictionary definitions of the key words. Put two pairs together and allow 5 minutes of discussion to refine answers and arrive at an agreed definition. Take feedback from each group, then read out the dictionary definition and compare answers. 4. To introduce the key words for the major food groups Put anagrams or scrambled letters of the following words on the board or OHT: sugar, starch, carbohydrate, protein, fibre, vitamins, minerals, water Ask pupils to unscramble them to find the names of the food groups. When all the words are complete, ask pupils to put their hands up and check whether they are correct. Allow a maximum of 5 minutes for this activity.

4 4 of 5 5. To find out functions and sources of the major food groups Assign pupils to groups of three or four, providing each group with appropriate text books or access to a computer with the necessary software. At the front of the classroom arrange a pile of questions per group. If possible, have the piles colour-coded so that each group can easily identify their own questions. Some questions are provided on page 5. One pupil collects a question from their group s pile and returns to the group who research the answer. A different pupil returns to the teacher, has the question marked and selects another question from their group s pile of questions. The first group to complete all their questions, wins. The winning group has to explain to the other groups the answers to any questions the other groups failed to answer. 6. To familiarise pupils with the concept of a balanced diet Divide pupils into groups of three or four. Provide each group with textbooks and/or computers with appropriate software. Each group designs a three-course dinner that has a balance of the food groups and would be considered healthy. Groups display their menus and explain to the class why their meals are healthy and balanced. The rest of the class should be encouraged to ask questions about why the meal is balanced. Relevant Key Stage 3 national test question 2002 paper 1, tier 3 6 question 10

5 5 of 5 Questions 1. Name two types of carbohydrate. 2. Why do our bodies need carbohydrates? 3. Name two foods rich in starch. 4. Name two foods rich in protein. 5. Why do our bodies need protein? 6. Why do our bodies need fibre? 7. Name two foods rich in fibre. 8. Why do our bodies need the mineral iron? 9. Name one food rich in iron. 10. What disease does vitamin C prevent? 11. What mineral do we need for healthy bones and teeth? 12. Give two reasons why our body needs some fat.