We explain what the population in biology is and some examples. Individual and community, population density and population growth.
What is population in biology?
In biology , population or biological population is understood as the set of organisms of the same species (animal, plant, etc.) that coexist in space and time , and that share biological properties. The latter implies that the group has high reproductive and ecological cohesion, that is, that individuals exchange genetic material (that is, they reproduce with each other) and share interactions and requirements for survival.
It is also usual to call a group of organisms that only cross (reproduce) each other , due to environmental isolation or similar conditions, since they would be perfectly capable of reproducing with some other foreign member of their species . This use is specific to genetics and evolution .
The same species can have several populations , each in a given area that serves as habitat . These can exist totally independently and independently, or they can be merged or divided according to their environment and the survival needs that arise. Thus, populations can grow, decrease, migrate or even spread among other local populations, which is called metapopulations.
The branch of biology that deals with research and study populations is precisely the biology of populations. According to her, we can talk about various types of biological populations, which are:
- Family populations Those in which the kinship relationship is central and common among the individuals that constitute them, that is, they are all family .
- Gregarious populations. Those formed by the shifting mass of individuals, who need not have any relationship, but come together for reasons of safety and economy of resources.
- State populations Those whose members have a high degree of diversification and specialization, distributing the work and not being able to live in an isolated and individual way.
- Colonial populations. Those constituted by individuals that come from a more primitive one, to which they are bodily united, constituting a network or colony of very similar organisms.
Examples of population in biology
Some simple examples of the four previous population types would be the following:
- Family population A pack of lions, composed first of all by the male and female who have numerous offspring, and which in many cases can be made up of several females and a dominant male. The human family could also be an example of this.
- Gregarious population. The schools of fish, to which individuals are added regardless of their affiliation or genetic origin, mobilizing together, eating together and ensuring better chances of survival than being alone.
- State population The ideal example of this is a beehive of ants, within which numerous individuals coexist, each endowed with very specific functions: workers, soldiers, fertilizing males and a queen who lays eggs. None of them can live separately.
- Colonial population A good example is the coral populations at the bottom of the seas, where they spread slowly and spread their colony on the seabed or on stones, sharing the same body mass among individuals.
Individual and community
Every living being, of whatever species, constitutes an individual . As such, it is unique in many ways, has a unique and unrepeatable existence, and a genetic code that reflects it. However, in most cases, living beings prefer to live among peers, that is, as part of a specific population that, in turn, makes life within an ecological community .
Thus, if biological populations are groups of individuals of the same species that share their habitat and that usually reproduce among themselves, a community instead is the set of populations of different species that share the same habitat. That is, the sum of the populations of the same habitat forms a certain community, in which there are intra and extra species interactions that determine a trophic chain .
The density of a biological population has to do with how concentrated the individuals that compose it are in the specific area of their habitat . That is, how tightly they live, to put it in simple terms. This is usually measured in individuals per unit area, for example, individuals per square kilometer, and it is an average, an approximation to understand how close the individuals of a population are to each other.
Thus, when the population density is low, that is, few individuals per square kilometer, there will be a lot of surface between one individual and another, so it will be more difficult to find them. However, when the population density is high, it will be easier to get an individual and they will be closer to each other, since there will be more in the same unit of space.
Population growth is understood as the increase or decrease of the total number of individuals in a population at a given time . Populations grow when the number of births (rate of birth ) exceeds the number of deaths (mortality rate), or when they receive migration of individuals from other populations. And similarly, populations decrease when the number of deaths exceeds that of births, or when a number of individuals migrate to some other population. In those cases where the birth rate and death rate is comparable, it will be said that it presents a growth equal to zero, that is, neither grows nor decreases, remains stable.