Topic 5
Keys
Coursebook section 1.7 Teaching ideas ◆
Students normally find using a dichotomous key very easy. Show them how to use the key on page 15 in the Coursebook. Then provide a key that you have written yourself to enable the identification of different kinds of trees that grow in your school grounds. Ideally, allow the students to go outside to identify selected trees; otherwise, bring small branches or individual leaves into the classroom. (For future lessons, you may be able to use keys that your students have written in previous years.) ◆ Students could then be asked to construct their own keys. Worksheet 1.3 provides material for this, and so do Figure 1.23 and end-of-chapter question 4. It would also be an excellent idea to ask students to construct keys to identify a small range of animals or plants that can be found in the school grounds. Common misunderstandings and misconceptions ◆
Students may try to use a key by looking at all the organisms at once and trying to match them against descriptions, rather than looking at just one organism and working systematically through the key to identify it. ◆ When writing keys, they may use terms such as ‘long’ or ‘dark’, which are subjective and therefore not useable by a person looking at just one type of organism. All descriptions should be objective, as explained on Coursebook page 16. Homework ideas ◆ ◆ ◆ ◆ ◆
Workbook exercise 1.2 Using keys Worksheet 1.3 Writing a key Question in the caption of Figure 1.23 in the Coursebook End-of-chapter question 4 Construct a key to identify the leaves of five trees that grow in the school grounds
Original material © Cambridge University Press 2014 © Cambridge University Press 2014
IGCSE Biology
Chapter 1: Teaching ideas
5