Biotic potential: what it is and how it is shaped in biological evolution
Biotic potential explains why sometimes a group of living things expands rapidly.
The goal of every living thing on this planet is the expansion of its genes, in one way or another. Animals develop their behaviors, behaviors and anatomical adaptations based on a very simple premise: to leave their mark on the following generations in the form of their own or other inbred offspring (cousins, siblings, etc.). Even at the cost of its life, the only thing that the living entity ultimately seeks is, without a doubt, to have children.
According to the theory of natural selection, the biological evolution of living organisms depends on environmental pressures and interactions with other species.. When an animal suffers a spontaneous mutation in its development, it may have a biological advantage over the rest, for example, an insect may be born with slightly larger jaws. If this insect lives longer than the others because it obtains food more easily and the trait is heritable, it is expected to have more offspring than the others.
Thus, the character "large jaws" can expand in a population because it increases the biological fitness of the species: insects with this mutation will reproduce more easily, so offspring with this trait will become more and more common. What happens when a species reaches an adaptive pinnacle based on accumulated adaptations? Is there a limit to the expansion of a species? We cover these topics and many more in the following lines, as we tell you all about biotic potential.
The reproductive potential of living beings
Before moving on scales of populations and species, it is necessary to look at the potential of each of the members of them. For this reason, it is time to take a general look at fitnessfitness, aptitude or biological suitability.
Fitness is defined as a quantitative representation of the natural selection mechanisms that act on the adaptation of living beings to the environment. Put more simply, this parameter shows the proportion of genes that an individual of a species leaves in the next generation, with respect to the total gene pool present in the population in which it lives..
Colloquially, fitness is conceived as the number of children a parent has during his or her lifetime, but siblings, cousins and other Blood relatives are also part of the individual's gene pool. Thus, the fitness rate of an organism is sometimes defined not only by how attractive it is to females, but also by its ability to maintain a society or family unit afloat. ability to maintain a society or family unit afloat..
This term can be calculated with the following mathematical formula:
W: L x M
With W being the absolute fitness, L the survival of the individual and M its fecundity, the viability of a population over time can be calculated approximately. Finally, it should be noted that fitness can be absolute (number of offspring expected for an individual) or relative (number of offspring in relation to the other conspecifics). In general, the higher the fitness of each member of a population, the better the performance of the species in its ecosystem.
What is biotic potential?
In colloquial terms, it could be said that biotic potential is the consequence of a high fitness sustained over time in a population of a given species. the consequence of sustained high fitness over time in a population of a given species.. If we take a more technical approach at the biological level, this term can be defined as the unrestricted growth of a species in an ecosystem, up to the point at which the maximum population rate is reached.
As you can imagine, this does not happen in nature, except on very rare occasions that are influenced by factors exogenous to the ecosystem (such as the release of exotic species in an environment that is not their own). For the biotic potential to develop, the species in question must be free of predators, not carry diseases and have a practically unlimited availability of resources. Natural selection mechanisms themselves prevent this from happening, otherwise ecosystems would eventually collapse, ecosystems would eventually collapse.
At a mathematical level, the biotic potential can be obtained and applied by the following two formulas:
- Number of individuals= biotic potential/environmental resistance (living + non-living).
- Vital index= (number of births/number of deaths) x 100
The probability of reaching the biotic potential increases the more adaptations or tools a species has to face natural selection and genetic drift, the two main processes that shape the evolution of living beings over the centuries. In any case, as we have said, it is impossible to be perfectly adapted to an environment, since natural impositions prevent this from happening.
The components of biotic potential
As indicated by renowned ecologists who have developed this parameter (such as R.N Chapman), the biotic potential is composed of two different sections: reproductive potential and survival potential..
The first term is closely related to fitness: the more offspring each individual has, the better, as the birth rate will tend to exceed the mortality rate.
In any case, a particularly fit specimen may lay 2,700 eggs in one sitting, but all of them may end up in a single bite in the stomach of a predator. Therefore, it is not only the number of offspring that can be taken into account: it is also essential to record that the offspring survive over time.
Biotic potential = reproductive potential + survival potential
Why do species not reach biotic potential?
To answer this question, we have to go back years ago, to Isaac Newton's third law of motion:
If object A exerts a force on object B, then object B must exert a force of equal magnitude in the opposite direction on object A..
Let's apply this premise in a biological setting. If a rabbit population begins to grow because climate change has encouraged the development of certain species of grasses on which these lagomorphs feed, it is to be expected that predators will grow exponentially in the ecosystem, predators are expected to grow exponentially in the given ecosystem in response to the presence of more herbivores. ecosystem in response to the presence of more herbivores.
If more and more rabbits are available, the females will be able to eat more before giving birth, so expect larger litters. In addition, since there is more prey, the survival rate of the cubs will be higher, since the weaker specimens will not die of starvation. If there are more predators due to the increase in prey, it is logical that the number of prey will decrease over time, thus tending to stabilize the balance again.
In the ecosystem, every action has a diametrically opposite reactionunless the dynamics are not naturally conceived within the environment. Let's take another completely different example: the human being.
As you can imagine, the human being is the only example of a species that has reached the biotic potential in a sustained and evident way. The population numbers of our species are growing at an exorbitant rate, but since we have gotten rid of predators, we have extremely efficient production systems and it is difficult for diseases to kill us, there is no regulatory mechanism to bring the biological balance back to normal.
Therefore, our species is at a tipping point, our species is at a point of biotic potential, at least for the time being.. No matter how much we develop technology and move away from natural selection mechanisms, one thing is clear: resources are still not unlimited.
Thus, we can conclude with the following idea: biotic potential is the stage that is reached when living beings are freed from any environmental imposition and grow as much as they can at the population level up to the maximum possible. For biotic potential to take place, animals not only have to reproduce a lot, but also the offspring must survive over time.
In a natural ecosystem, it is not conceivable for a species to reach the biotic potential in the long term: at some point resources will run out and, if this is not the case, predators in the area or other species will take it upon themselves to prevent the given population from expanding. Fortunately or unfortunately, we are the only ones who have been in this state of continuous expansion for thousands of years, with all the good and bad that goes with it.
(Updated at Mar 28 / 2023)