(a) :The transfer of food energy from producers to consumers through a series of organisms with repeated eating and being eaten is known as food chain. Green plants are always the first link of food chain because they alone are capable of synthesising organic food by using light energy by photosynthesis. The logical sequence of a food chain is : Producer → Consumers → Decomposer Small plants ( Primary producer ) → Zooplanktons ( Primary consumer ) → Fish ( Secondary consumer ) → Man ( Tertiary consumer)