In the following food chain, 100 J of energy is available to the lion. How much energy was available to the producer? Plants ⟶ Deer ⟶ Lion

In an ecosystem, energy flow is unidirectional and follows the 10% law. This law states that during the transfer of organic food energy from one trophic level to the next higher level, only about 10% of the chemical energy is stored as flesh. The remaining 90% is lost during transfer, broken down in respiration, or lost to incomplete digestion. Working backwards from the top consumer (Lion, $100\text{ J}$), the primary consumer (Deer) must have had $1,000\text{ J}$ ($100\text{ J} \times 10$), and the producer (Plants) must have had $10,000\text{ J}$ ($1,000\text{ J} \times 10$).