Explain the importance of autotrophic organisms with respect to energy flow and nutrient cycling in ecosystems.

Autotrophic organism are the base pillars of the ecosystem which maintains the flow of nutrients and energy in an ecosystem.

The energy from the sun is converted in the form of chemical energy which is first used by the plants and then passed on to the next organism.

If there will be no autotrophs then there will be no flow of energy as no organism can trap sunlight and transfer energy to another levels.

Hence, the flow of energy and nutrients is like Sun → Producers→ Primary consumers→ secondary consumers→ tertiary consumers.

it has one origin of replication, but it proceeds in two directions - d)