The loss of energy and biomass from trophic level to trophic level is considered to prevent food chains from becoming any longer. Four trophic levels is common, and five can exist. It is rare to have a food web made of chains longer than five trophic levels.

Samples would be taken several times over the year to find the all the organisms in a 1m² quadrat.
The energy contained in the biomass of these organisms will be measured (or calculated)
kilojoules are the units of energy.

The sun provides energy to ecosystems, continuously, and it is trapped in organic molecules by photosynthesis. Inorganic nutrients are recycled by decomposers but when they are reabsorbed into plants they don't contain very much energy.

As energy is lost from each organism through respiration only about 10% of the energy gets passed to the next trophic level. It is not always 10% exactly. In fact in this example it is never 10% exactly, but close to this number.

Producers are photosynthetic, primary consumers eat producers, and secondary consumers eat primary consumers. The situation is complicated this this model, because the large zooplankton could be described as a primary consumer or a secondary consumer, because it eats large phytoplankton.

Decomposers take energy from dead organic material, and bacteria can behave as a saprotroph when it decomposes detritus. Bacteria can also be photosynthetic, e.g. blue/green bacteria.
If the bacteria can use sunlight to make organic molecules, then the are producers.

No organisms can "make energy". Beware of this phrase, it is a common mistake.

Energy enters almost all ecosystems as sinlight in photosynthesis. This is the role of producers.
A very few organisms can use inorganic molecules as a source of energy.

Glucose is used in the process of respiration. It is eventually lost to the ecosystem in the form of heat.

The majority of heat present in organisms is lost to the environment as heat. Much of this is generated as a by-product of respiration.
Faeces contains energy but it is not lost to the ecosystem because it is used by saprotrophs. Evaporation is not a form of energy.

Respiration converts the chemical energy in glucose, fats or proteins to ATP and heat. When the ATP is utilised its energy is lost as heat.
Heat cannot be concentrated and utilised by living organisms in their metabolism, although some animals do absorb some heat to warm their bodies.

Most ecosystems depend upon light energy as a primary source but some can use chemical energy (particularly Arcaeans living in extreme environments such as thermal vents, deep sea)

Energy lost at one level of a food chain is not available for the next level. Heat, egestion, death and decay and excretion represent loss of energy from each level not available to the next level

In the second trophic level the energy enters in the form of consumption of nutrients from plant material.
While heat is lost to the environment, and undigested material is lost to decomposers.

Each successive trophic level in a food chain has less energy availability due to loss so chains are limited in length. Populations at each level depend upon energy available and also on size (e.g. insects feeding from a tree)

Energy lost at one level of a food chain is not available for the next level so the biomass of organisms at each level will decrease.

Eating plant material (2nd trophic level) gives the maximum amount of energy for a population - every level above the 2nd contains less energy because at each trophic level energy is lost to the environment.

Biomass refers to the mass of living tissue in a population.

An estimate is taken from a representative sample. From this an estimate of the size of the population is made and then a measure of the mass or the sample captured.

Feeding passes chemical energy up the food chain when it is assimilated.

Carbon dioxide, oxygen and water are recycled, energy cannot be recycled.

All the chemical elements utilised in ecosystems are recycled.