(a) (i) Plants capture only about 1% of the solar energy that falls on them and use it for photosynthesis.
(ii) On average, only about 10 percent of energy stored as biomass in a trophic level is passed from one level to the next. This is known as " 10 percent rule" and it limits the number of trophic levels an ecosystem can support.
(b) The various steps in a food chain or ecological pyramid, at which the transfer of food (or energy) takes place from one organism to another organism is known as trophic levels. Based on the source of their nutrition or food, organisms occupy a specific place in the food chain. Organisms in food webs are grouped into categories called trophic levels, these levels are divided into producers (first trophic level), consumers, and decomposers (last trophic level). There is only 10% flow of energy from one trophic level to the next higher level. The loss of energy at each step is so great that very little usable remains after four or five trophic levels. Hence only 4 to 5 trophic levels are present in each food chain.