Yes, the pyramid of energy is typically unidirectional in a food chain, with energy flowing from primary producers (usually green plants) to higher trophic levels. Green plants are the first trophic level in a food chain because they can capture and convert solar energy through photosynthesis, making them the primary source of energy for other organisms in the ecosystem. Their ability to produce their own food forms the foundation of most food chains and sustains life in ecosystems.

Dr S J Malik and Dr Rana Hamza Shakil thank you for your contribution to the discussion

The flow of energy is always unidirectional. The energy passes from primary producers to primary consumers. From primary consumer the energy passed to secondary consumers and then to teritary consumers. Thus the energy pyramid is always upright. It is evident from the energy flow that there is always a gradual decrease in the energy content at every successive trophic level from the producer to the top consumers. Hence the energy pyramid is always upright. Pyramid of energy is the only pyramid that can never be inverted and is always upright. This is because some amount of energy in the form of heat is always lost to the environment at every trophic level of the food chain. It is measured in terms of energy per area per time. The flow of energy in food chain in unidirectional because the sun is the only source of energy for all ecosystems on earth. Then the energy is captured by the autotrophs does not revert back to the sun. Therefore, in the food chain, the energy moves progressively through various trophic levels. The first and lowest level contains the producers, green plants. The plants or their products are consumed by the second-level organisms the herbivores, or plant eaters. At the third level, primary carnivores, or meat eaters, eat the herbivores; and at the fourth level, secondary carnivores eat the primary carnivores. The first trophic levels are producers in a food chain which includes green plants. It is the lowest trophic level. The reason behind producers placed on the first trophic level is that they have the capability to transfer solar energy into food.Green plants use sunlight and carbon dioxide from the atmosphere to produce carbohydrates by the process of photosynthesis. Since plants produce food for themselves, they are known as producers. So, they are the first link in any food chain. All food chains start with producers. Green plants prepare their own food and they are called producers. They always occupy the first level of a food chain.Producers are organisms that can make their own food by the process of photosynthesis. Ex. algae and green plants etc. In every food chain, green plants are producers. Producers always occupy the first trophic level in any food chain because only producers have the ability to trap solar energy with the help of chlorophyll and synthesis their own food. Green plants are producers. The first trophic level in a food chain is the producers i.e. those organisms which produce food by photosynthesis. The bottom and largest level of the pyramid is the producers and contains the largest amount of energy. As you move up the pyramid, through the trophic levels to primary, secondary and tertiary consumers, the amount of energy decreases and the levels become smaller.