Star with the Sun and describe what happens to energy though the trophic levels. why does this not go on forever (with many more trophic levels?

1)
Only 10% of energy from each trophic level is passed on to the next; therefore, the energy passed to the primary consumer will be only 10 kcal. This means that the number of primary consumers can not be as high as that of the primary consumers due to the lower amount of energy they receive.

2)
If a producer is removed from an ecosystem, then there is less energy entering the ecosystem. The ecosystem would be not sustained properly.
If a tertiary consumer is introduced, it is likely to give competition to other higher level consumers. It will also decrease the number of secondary consumers, meaning their numbers will dwindle, which will cause the numbers of the tertiary consumers to remain low.