In an ecosystem, the trophic levels refer to the different levels of organisms in a food chain or food web based on their feeding relationships. There are typically four or five trophic levels, depending on how the ecosystem is structured. These trophic levels are:

1. **Producers (Autotrophs):** These are organisms that produce their own food through photosynthesis or chemosynthesis. They convert energy from sunlight or chemicals into usable energy for themselves and other organisms in the ecosystem.

2. **Primary Consumers (Herbivores):** These organisms eat producers (plants or algae) as their primary source of energy. They are the first level of consumers in the food chain.

3. **Secondary Consumers (Carnivores or Omnivores):** These organisms feed on primary consumers. They are the predators that consume herbivores or other omnivores.

4. **Tertiary Consumers (Carnivores):** These are organisms that feed on secondary consumers, which can be carnivores or omnivores.

5. **Quaternary Consumers (Top Predators):** In some ecosystems, there might be a fourth level of consumers that feed on tertiary consumers.

The least amount of energy is typically available at the highest trophic levels, especially the quaternary consumers or top predators. This is because energy is lost at each trophic transfer in the form of heat during metabolic processes, movement, and waste production. This phenomenon is known as the "trophic efficiency" or "ecological efficiency." As a result, the higher up you go in the food chain, the less energy is available compared to the lower trophic levels.

Regarding the amount of available biomass at each level of a biomass pyramid, the pyramid illustrates the distribution of biomass (the total mass of living organisms) at each trophic level. In general, the biomass pyramid shows a decrease in biomass as you move from lower to higher trophic levels. This is due to the fact that energy is lost at each trophic level, and because organisms at higher trophic levels require more energy to sustain themselves.

For example, let's consider a simplified biomass pyramid in a terrestrial ecosystem:

- Producers (Plants): Highest biomass, as they capture the most energy from the sun.

- Primary Consumers (Herbivores): Lower biomass compared to producers, as they need to consume large amounts of plant material to sustain themselves.

- Secondary Consumers (Carnivores): Even lower biomass, as they need to consume multiple herbivores to meet their energy needs.

- Tertiary Consumers (Top Carnivores): Lowest biomass, as they are at the top of the food chain and must expend a lot of energy to catch their prey.

In aquatic ecosystems, the biomass pyramid can sometimes be inverted, where the biomass of consumers (such as fish) can outweigh the biomass of producers (such as phytoplankton). This is because aquatic ecosystems tend to have faster turnover rates and can support higher consumer biomass relative to the primary producer biomass.

Remember that these patterns can vary based on the specific ecosystem, the types of organisms involved, and environmental factors.

Dr Gaurav H Tandon thank you for your contribution to the discussion

The green plants in the ecosystem are producers and they make the first trophic level of the food chain having the greatest amount of energy. It follows that the carnivores that feed on herbivores and detritivores and those that eat other carnivores have the lowest amount of energy available to them. Energy decreases as it moves up trophic levels because energy is lost as metabolic heat when the organisms from one trophic level are consumed by organisms from the next level. Trophic level transfer efficiency (TLTE) measures the amount of energy that is transferred between trophic levels.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. Since they are the base of the pyramid, the producers are the level within ecosystems that have the most energy available-followed by the primary consumers, secondary consumers, and then the tertiary consumers. The amount of energy available to one trophic level is limited by the amount stored by the level below. Because energy is lost in the transfer from one level to the next, there is successively less total energy as you move up trophic levels. The other 90 percent of the energy is needed by organisms at that trophic level for living, growing, and reproducing. This relationship is shown in the energy pyramid above. It suggests that for any food chain, the primary producer trophic level has the most energy and the top trophic level has the least.The pyramid of biomass shows the flow of energy from producers to consumers. We know that only 10 per cent of the energy gets transferred to the next trophic level and the rest is either utilised for metabolic processes or excreted out. In fact, only about ten per cent of the biomass is transferred from each trophic level to the next. The remaining 90 per cent is used by the trophic level to complete life processes. Biomass can be lost between stages because not all of the matter eaten by an organism is digested. Biomass is lost between the different trophic levels. Producers are mostly plants and algae which transfer about 1 % of the incident energy from light for photosynthesis. Only approximately 10 % of the biomass from each trophic level is transferred to the level above it. Biomass in an ecological pyramid is lost progressively from the bottom up. The greatest biomass amount is found at the base trophic level that includes the producers. The number of organisms at each level decreases relative to the level below because there is less energy available to support those organisms. The top level of an energy pyramid has the fewest organisms because it has the least amount of energy.