underline the difficult words or structures and raise their questions concering any difficulties their may have in their understanding of the text,the teacher is responsible for helping them resolve the above problems. Discussion organization(ten minutes) When the predictions of an optimisation model disagree with what is found in nature.there are two possible explanations.Oe is that the mode is at fault.importan constraints may not have been identified Another reason is that the structure or behaviour under investigation is suboptimal Part V.Assignment: Exercises: Why may reproduction conflict with survival?