Q.Why can a single food chain generally not support more than four or five trophic levels?

Applying the 10% law twice (producers→herbivores→carnivores) from 5000 J gives 50 J reaching secondary consumers.

According to Lindeman's ten percent law, only about 10% of the energy present at one trophic level is transferred to and becomes incorporated as biomass at the next trophic level; the rest is lost mainly as heat through respiration and other metabolic processes. Starting with 5000 Joules of light energy captured by the producers: primary consumers (herbivores) would receive about 10% of this, i.e., 5000 × 10/100 = 500 Joules. Secondary consumers (carnivores, i.e., the level asked about) would then receive about 10% of the herbivores' energy, i.e., 500 × 10/100 = 50 Joules. So 50 Joules of energy would ultimately …

Applying the 10% law twice: 1000 J → 100 J → 10 J reaches the lion.

Energy flow through a food chain is unidirectional and follows Lindeman's 10% law: at each trophic transfer, only about 10% of the energy received is passed on to the next level, the rest being lost as heat during respiration, used in metabolism, or left undigested. Starting with 1000 J captured by the producers (plants), the herbivore (deer) receives about 10% of this, i.e. 100 J. The carnivore (lion), one level …

Green plants photosynthetically use only about 2-10% of the total solar energy that falls on them.

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Sunlight reaching a plant canopy is far from fully converted into chemical energy through photosynthesis. Much of the incident solar radiation is: reflected off leaf surfaces, transmitted straight through the leaf without being absorbed, absorbed but outside the photosynthetically active radiation (PAR) waveband (400-700 nm), or absorbed as PAR but lost as heat rather than being fixed. As a result, in most natural ecosystems, only a small fraction of the total incoming solar energy -- about 2-10% -- is actually captured and fixed by green plants during photosynthesis and made available a …

Green plants use only about 2-10% of incident solar energy for photosynthesis.

Only a portion of the sunlight that falls on a leaf is of a wavelength and intensity that chlorophyll a, chlorophyll b and the accessory pigments can actually absorb and channel into the light reactions of photosynthesis; much of the incident radiation is reflected off the leaf surface, transmitted straight through, or absorbed and simply dissipated as heat rather than being converted into chemical energy. Because of these physical and biochemical losses at every stage -- reflection, transmission, non-photosynthetic absorption and the inherent inefficiency of converting light energy into ATP and NADPH -- ecologists estimate that green plants effectively use only about 2 to 1 …

Green plants convert only about 2-10% of incident solar radiation into chemical energy via photosynthesis.

A leaf receives the full spectrum of incident sunlight, but only the visible, Photosynthetically Active Radiation (PAR) band can be absorbed by chlorophyll and accessory pigments, and even within PAR much of the energy is lost to reflection, transmission through the leaf, and non-photochemical heat dissipation. As a result, under natural field conditions the overall efficiency with which green plants convert incident solar energy into the chemical energy of photosynthate is only about 2-10%, and this trapped fraction is what constitutes the gross primary productivity (GPP) of an ecosystem, the base on which all subsequent trophic levels depend. This low first-step efficiency, comp …