What is the 10% rule in energy transfer?

The 10% rule in energy transfer refers to the fact that, in an ecosystem, only about 10% of energy is passed from one trophic level to the next.

In more detail, the 10% rule is a principle in ecology that describes the energy flow within a food chain. It states that when energy is passed from one trophic level to the next, only about 10% of the energy is transferred, while the rest is lost as heat. This is due to the second law of thermodynamics, which states that whenever energy is transferred or transformed, a significant portion is lost as heat.

For example, if a plant absorbs 1000 units of sunlight energy, it will only be able to convert about 100 units into chemical energy through photosynthesis. When a herbivore eats this plant, it will only gain about 10 units of this energy, and a carnivore that eats the herbivore will only receive about 1 unit of energy. This is why food chains typically have only four or five trophic levels - there simply isn't enough energy to support more.

This rule also explains why there are usually fewer organisms at higher trophic levels. Since less energy is available at each successive level, fewer organisms can be supported. For instance, a field might support thousands of plants, but only hundreds of herbivores and tens of carnivores.

The 10% rule is a fundamental concept in understanding how energy flows through ecosystems, and it has important implications for the structure and function of ecological communities. It's also a key factor in the management and conservation of wildlife populations, as it helps us understand the carrying capacity of different habitats.