In tropical rain forests,most of the energy in the ecosystem flows through:

The percentage of energy transferred to the higher trophic level in a food chain is ....... (in $\%$)

Identify the correct food chain.

The driving force of any ecosystem is

Give an account of energy flow in an ecosystem.

Assertion $A$: Heat energy is available for the functioning of a system.
Reason $R$: Some amount of energy is lost during energy transformation.
Which option is correct for Assertion $A$ and Reason $R$?