Homeostasis & feedback (CIE A-level bio)

This lesson describes the importance of homeostasis in mammals and focuses on the parts of a control system and negative feedback . The detailed and engaging PowerPoint and accompanying resources have been designed to cover the content of points (1 and 2) of topic 14.1 of the CIE A-level biology specification, but positive feedback is also discussed to broaden student understanding.

As homeostasis is a topic met at GCSE, this lesson has been written to build on this knowledge as well as to check on their prior knowledge of earlier A-level topics such as osmosis when considering blood water potential and the use of glucose as a respiratory substrate. Discussion points are written into the lesson at regular intervals to encourage the students to consider why a particular process or method takes place and understanding checks allow them to assess their progress. Students will recall how body temperature, blood water potential and blood glucose concentration are maintained within restricted limits and the importance of these systems are looked into in detail. Time is taken to consider the importance of maintaining these aspects, specifically with relation to the activity of enzymes. As such, students will also discuss how the pH of the blood is maintained. The key components of the control system are recalled and then time is taken to focus on the cell signalling that occurs between the coordination centre and the effectors. Students will learn to associate the response with either the use of the nervous or endocrine system. The final part of the lesson looks at the importance of negative feedback in reversing the change in order to bring the aspect back to the optimum and the added degree of control which this provides. Positive feedback is also briefly mentioned at the end.