por What is biotic potential?
He biotic potential is the maximum growth rate of a population in which there are no restrictions. For a population to reach its biotic potential, it must have unlimited resources, there must be no parasites or other pathogens, and species must not compete with each other. For these reasons, the value is merely theoretical.
In reality, a population never reaches its biotic potential, since there are a series of factors (biotic and abiotic) that limit the indefinite growth of the population. If we subtract environmental resistance from the biotic potential, we will have the real value of the rate at which said population increases.
intrinsic growth rate
Biotic potential is also known as intrinsic growth rate. This parameter is denoted by the letter r and is the rate at which the population of a certain species could grow if it had unlimited resources.
Organisms that possess high intrinsic growth rates generally reproduce early, have short generation times, can reproduce several times in a lifetime, and have a large number of offspring at each reproduction.
According to these characteristics and life strategies, the species can be classified as prodigal or R strategies and prudent or K strategy. This classification was coined by George Hutchinson.
The r strategies are characterized by giving birth to a high number of offspring, these are small, their maturation period is fast and they do not spend time on parental care. Logically, the reproductive strategies r reach the maximum capacity of the biotic potential in terms of reproduction.
In contrast, species listed as K have few offspring, are slow to mature, and have large body sizes. These species care intensely for their young to ensure their success.
Factors Affecting Biotic Potential
The biotic potential is influenced by a variety of factors intrinsic to the species. The most relevant are described below:
The frequency of reproduction and the total number of times the organism reproduces. For example, bacteria reproduce by binary fission, a process that can take place every twenty minutes. Instead, a bear has cubs every three or four. When comparing the biotic potentials of both, the polar bear has a much lower potential.
The total offspring born in each reproductive cycle. Bacterial populations have very high biotic potentials. Given unlimited resources and no restrictions, a bacterial species could form a 0.3-meter-deep layer that could cover the Earth’s surface in just 36 hours.
The age at which reproduction begins.
The size of the species. Species with small body sizes, such as microorganisms, generally have a higher biotic potential than species with larger body sizes, such as some mammals.
environmental resistance
The biotic potential of a species is never reached. Factors that prevent unrestricted growth are known as environmental resistances. These include various pressures that limit growth.
Within these resistances are diseases, competition, accumulation of some toxic waste in the environment, unfavorable climatic changes, scarcity of food or space, and competition between species.
That is, the exponential growth of a population (which occurs when it does not present any limitations) becomes logistic growth when the population faces these environmental resistances.
Over time the population stabilizes and reaches its carrying capacity. In this state, the growth curve takes the shape of an S (sigmoid).
Loading capacity
The environmental resistances together with the biotic potential determine the carrying capacity. This parameter is denoted by the letter K and is defined as the maximum population of a given species that can be maintained in a particular habitat without being degraded. In other words, it is the limit imposed by environmental resistances.
The population growth rate decreases when the population size approaches the value of the carrying capacity of the environment. Depending on the availability of resources, the population size can fluctuate around this value.
If the population exceeds carrying capacity, it is likely to collapse. To avoid this phenomenon, the surplus individuals must move to new areas or start exploiting new resources.
Biotic potential in humans
In humans, and other large mammals, the biotic potential can be 2-5% each year, in contrast to 100% biotic potential of microorganisms every half hour.
In human populations the full biotic potential is not reached. In biological terms, a woman is capable of having more than twenty children during her lifetime.
However, this number is almost never reached. Despite this, the human population has grown exponentially since the eighteenth century.
Example of biotic potential
Otters do not reach their biotic potential for various reasons. Females reach sexual maturity between 2 and 5 years of age. The first reproduction occurs at approximately the age of 15 years and on average they only have one young.
Regarding the population size, this is fluctuating due to environmental changes. The growth of predators such as orcas, also known as killer whales, decreases the population size of otters.
However, the natural prey of killer whales is not otters. They are sea lions and seals, whose populations are also declining. So to make up for it, orcas resort to feeding on otters.
Parasites are also a crucial factor in the decline of the otter population, specifically parasites from companion animals such as cats.
The parasites manage to reach the otters because pet owners flush their waste down toilets, contaminating the otters’ habitat.
Likewise, the contamination of the waters produced by humans has also contributed to the decrease in the number of otters.
The incidence of each one of these factors in the decrease of the biotic potential of the otters could be leading to the extinction of this species.