assistance.Fifteen minutes'discussion will be arranged.Some beautiful diagrams have been prepared for visualization. V Presentation(课堂讲解，学时分配为2学时左右) Step 1.Warm-up Activity Draw Food chain and web Step 2.The students are required to finish reading the whole text before the class and try to understand the major points of the chapter.The students are supposed to underline the difficult words or structures and raise their questions concerning any difficulties their may have in their understanding of the text,the teacher is responsible for helping them resolve the above problems Discussion organization(twenty minutes) Can all Chinese consume meats instead of grains?Why? Describe the importance of primary production? V.Assignment: 1.Write the trophic level that each organism belongs to in this food web How doesa food eb diffr froma food chain? 3 4.How much energy is used up at each trophiclevel (unavailable to the next)? 5.Agree or Argue:Highly productive ecosystems cannot support large numbers of secondary consumers. 6.Lindeman's law of trophic efficieney