Definition of a species and it’s state
An ecological pyramid (also trophic pyramid, eltonian pyramid, energy pyramid, or sometimes food pyramid) is a graphical representation designed to show the biomass or bio productivity at each trophic level in a given ecosystem.
Biomass is the amount of living or organic matter present in an organism. Biomass pyramids show how much biomass is present in the organisms at each trophic level, while productivity pyramids show the production or turnover in biomass.
Energy pyramids begin with producers on the bottom (such as plants) and proceed through the various trophic levels (such as herbivores that eat plants, then carnivores that eat herbivores, then carnivores that eat those carnivores, and so on). The highest level is the top of the food chain.
An energy pyramid of biomass shows the relationship between biomass and trophic level by quantifying the biomass present at each trophic level of an energy community at a particular time. It is a graphical representation of biomass (total amount of living or organic matter in an ecosystem) present in unit area in different tropic levels. Typical units are grams per meter2, or calories per meter2. The pyramid of biomass may be “inverted”. For example, in a pond ecosystem, the standing crop of phytoplankton, the major producers, at any given point will be lower than the mass of the heterotrophs, such as fish and insects. This is explained as the phytoplankton reproduce very quickly, but have much shorter individual lives.
One problem with biomass pyramids is that they can make a trophic level appear to contain more energy than it actually does. For example, all birds have beaks and skeletons, which despite having mass are not eaten by the next trophic level.
There is also pyramid of numbers which represent the number of organisms in each trophic level. They may be upright (e.g. Grassland ecosystem), inverted (parasitic ecosystem) or dumbbell shaped (forest ecosystem).
Pyramid of productivity
An ‘ecological pyramid of productivity’ is often more useful, showing the production or turnover of biomass at each trophic level. Instead of showing a single snapshot in time, productivity pyramids show the flow of energy through the food chain. Typical units are grams per meter2 per year or calories per meter2 per year. As with the others, this graph shows producers at the bottom and higher trophic levels on top.
When an ecosystem is healthy, this graph produces a standard ecological pyramid. This is because in order for the ecosystem to sustain itself, there must be more energy at lower trophic levels than there is at higher trophic levels. This allows organisms on the lower levels to not only to maintain a stable population, but also to transfer energy up the pyramid. The exception to this generalization is when portions of a food web are supported by inputs of resources from outside the local community. In small, forested streams, for example, the volume of higher levels is greater than could be supported by the local primary production.
When energy is transferred to the next trophic level, typically only 10% of it is used to build new biomass, becoming stored energy (the rest going to metabolic processes) (Pauly and Christensen, 1995). In this case, in the pyramid of productivity each step will be 10% the size of the previous step (100,000, 10,000, 1,000, 100, 10, 1, .1, .01).
The advantages of the pyramid of productivity as a representation:
- It takes account of the rate of production over a period of time.
- Two species of comparable biomass may have very different life spans. Thus a direct comparison of their total biomasses is misleading, but their productivity is directly comparable.
- The relative energy chain within an ecosystem can be compared using pyramids of energy; also different ecosystems can be compared.
- There are no inverted pyramids.
- The input of solar energy can be added.
The disadvantages of the pyramid of productivity as a representation:
- The rate of biomass production of an organism is required, which involves measuring growth and reproduction through time.
- There is still the difficulty of assigning the organisms to a specific trophic level. As well as the organisms in the food chains there is the problem of assigning the decomposers and detritivores to a particular trophic level.
- Nonetheless, productivity pyramids usually provide more insight into an ecological community when the necessary information is available.
- An ecological pyramid of numbers shows graphically the population of each level in a food chain.
The definition of a species and its state are relative to its ecological community and its state of equilibrium or non-equilibrium
There are two fundamental states for a species, for individual organisms and for ecological community’s state of equilibrium and state of non-equilibrium.
The ecosystem’s non-equilibrium states have two options recession or development accordingly a species or an individual organism can either have a negative or positive long-term or short-term EROEI.
- A species is defined as one only if it reaches equilibrium at any trophic position.
- An Apex Predator species is a predator residing at the top of a food chain upon which no other creatures prey. Apex predators are usually defined in terms of trophic dynamics, meaning that apex-predator species occupy the highest trophic level or levels and play a crucial role in maintaining the health of their ecosystems.
- An Apex Consumer species is defined as one only if it reaches equilibrium at the highest trophic position possible: An Apex Consumer is a non-predatory species that have no intraspecies competitors/predators and therefore position at the top of the food chain of its climax community (the carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water, and other necessities available in the environment).
A species that reach the level of Apex Consumer will include all of the following characteristics:
- The species size, weight, morphology and physiology will reach a constant static state
- The species lifespan and longevity are extended to the maximum
- The species as whole and most individuals will maintain consistent level of positive EROEI short-term (weekly/monthly) and long-term (yearly/lifetime).
- Reach and maintain an optimal size for maintaining the surplus (largest size possible for an organism while maintaining the maximal state of equilibrium)
- Energy used to make each individual is high
- Few offspring are produced
- Late maturity, often after a prolonged period of parental care
- Long life expectancy
- Individuals can reproduce more than once in their lifetime
- Most individuals live near to the maximum lifespan
The only way a species can maximize its energetic equilibrium is by reducing the energy invested in the necessity (productive activities):
Eating, mating and ensuring the survival of the minimum number of offspring’s that is required for maintaining the population size equilibrium in the climax community (maintain its trophic level of an Apex Consumer).
Minimalize the energy wasted on unproductive activities such as fighting, hiding, escaping etc. and counter-wellbeing lack of activities (sleeping, socializing etc.)
Every activity other than the necessity can jeopardize its energetic equilibrium constant; these activities are all the activities that result in a negative EROEI and are not directly contribute for eating, mating and parenting and the wellbeing activities involved (foraging, sleeping, playing, socializing etc.).
These activities are all related for a non-equilibrium state of a species and a non-equilibrium state of its environment (a state of disturbance or a state of succession) this activities are all related for Intraspecies and interspecies competition (resources, space, mating) and basic survival (not being injured or killed).
- Every strategy to address this kind of state is considered a non-equilibrium strategy:
Any type of social organization that consist outside the period of mating and parenting that is higher than a core family (one male and one female)
- Any need to invest high levels of energy before every cycle of breading in finding and winning a mate etc.
- With no need to develop social strategies an Apex Consumer invest in the individuals of the species to ensure both genders will have maximum level of equilibrium, it means that both genders have equal size, weight, morphology and physiology in a constant static state as well as life histories, longevity and maximal lifespan.
The highest level of energetic equilibrium that can be reached by a species is the ability to maintain consistent positive daily EROEI 365 days a year throughout its total lifespan. Only a species that can maintain the highest level of energetic equilibrium for long periods can reach the maximum extended longevity, lifespan and life histories.