The principle of conservation of energy or the first law of thermodynamics teaches us that energy is neither created nor destroyed, it only transforms. Furthermore, the second law of thermodynamics shows us that energy passes from an organized system to a more disorganized one. These two rules govern the energy flows of ecosystems. In ecological communities, energy is transferred from one organism to another, and part of it is lost in the form of heat or heat. Different tools are used in ecology to represent energy levels, including ecological pyramids.
Energy in the ecosystem
As we have already commented, it is essential to know the laws of thermodynamics , as they help us to understand how energy is obtained and transferred within the ecosystem . On the one hand, we have the producers, usually photosynthetic organisms, which are capable of using a primary energy source such as sunlight. Producers, thanks to sunlight, carry out photosynthesis where they transform that light energy into chemical energy and biomass. This biomass and energy is available to other consumers. Consumers can be classified into primary consumers, they feed directly on producers, so herbivores, secondary or predators would be included here, they feed on primary consumers and there could be a third class, tertiary consumers, which normally correspond with decomposers and are those that feed on detritus or dead organisms.
The terms of producers and consumers are related to the trophic level of the food chain in an ecosystem , that is, the position that organisms occupy based on their source of energy and their eating habits. On the other hand, in ecology, we speak of energy flow to refer to the set of transformations and movements of energy through trophic levels . Solar energy is partly transformed into chemical energy and partly into heat.
Ecological pyramids are a graphic representation that gives information about the trophic levels of an ecosystem . Each level is represented by a rectangle with a width proportional to the value it represents and they are normally staggered creating a pyramid shape, but sometimes the size of the steps can vary creating other types of pyramids. They can be about the number of individuals, the amount of biomass or the energy content of each of the trophic levels of an ecosystem.
Finally, we discuss what are the different types of ecological pyramids :
Ecological pyramids of numbers
They represent the number of producers, herbivores or primary consumers, carnivores or secondary consumers, and decomposers or tertiary consumers in the ecosystem. The typical pyramids are those where the producers are located at the base and have the largest number of individuals, followed by the herbivores in fewer numbers and lastly the carnivores and decomposers, still in smaller numbers. These can be more or less pronounced, that is, for the same number of producers, the number of herbivores and carnivores can be greater or less, as long as what is explained above is fulfilled. There may also be ecological pyramids of inverted numbers, where the largest number of individuals is at the top of the pyramid and the smallest at the bottom.
Ecological pyramids of biomass
They represent the grams or kilograms of carbon in each surface or volume, that is, how many kilos of carbon are produced at each trophic level. The most common pyramid is the one where producers produce the most carbon, followed by primary, secondary, and tertiary consumers. However, there may be an investment between primary consumers and producers as in marine ecosystems. The marine phytoplankton grow and reproduce rapidly, but despite this, it is eaten even faster by primary consumers, and this is usually represented as an inverted pyramid.
Ecological pyramids of energy
They represent the flow of energy in the ecosystem. Since energy is transmitted from producers to other consumers, there is only one type of pyramid. The producers are located at the base of the pyramid, since they represent the photosynthetic organisms that take advantage of solar energy to transform inorganic matter into organic matter and make it available to the rest of the organisms, then primary consumers will be placed and finally the secondary ones. and tertiary. For every 100 calories of solar energy used by producers, only 10 calories will be converted into usable biomass for primary consumers. The rest of that energy is used by producers in metabolism, in structures such as dead leaves or stems in the case of plants and in other processes.