Answers are:
6. 100% of the energy that comes into an ecosystem comes in at the level of the producer which gets its energy from the sun to make its own food by photosynthesis.
7. Energy in an ecosystem is lost at a rate of 90% per trophic level. Only 10% gets transferred to the next level.
8. At tertiary consumer level there are least number of organisms present because very less energy is available to them from the preceding trophic levels.