Population in Biology – Concept, examples and growth

We explain what population is in biology and examples. Individual and community, population density and population growth.

The same species can have several populations, each one in a certain area.

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 presents a high reproductive and ecological cohesion, that is, that the individuals exchange genetic material (that is, they reproduce with each other) and share interactions and requirements for survival.

It is also usual to call population to a group of organisms that only interbreed (reproduce) with each other, due to conditions of environmental isolation or similar, 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 one in a certain area that serves as its habitat. These can exist in a totally autonomous and independent way, 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 researching and studying populations is precisely population biology. According to her, one can speak of various types of biological populations, which are:

  • Family populations. Those in which the kinship tie is central and common among the individuals that constitute them, that is, they are all family.
  • Gregarious populations. Those formed by the massive displacement of individuals, who do not need to have any kinship, but come together for reasons of security and economy of resources.
  • State populations. Those whose members present a high degree of diversification and specialization, dividing the tasks and not being able to live in isolation and individually.
  • 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 populations

Lion pride - population
A family population is made up of the male, the female, and a large number of offspring.

Some simple examples of the above four population types would be the following:

  • Family population. A pride of lions, composed first of all by the male and the 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 parentage or genetic origin, moving together, eating together and guaranteeing better chances of survival than being alone.
  • State population. The ideal example of this is an ant hive, within which numerous individuals coexist, each one endowed with very specific functions: workers, soldiers, fertilizing males, and a queen who lays her eggs. None of them can live separately.
  • Colonial population. A good example is the coral populations at the bottom of the seas, where they slowly spread 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 respects, it has a unique and unrepeatable existence, and a genetic code that reflects it. However, in most cases living beings prefer to live among pairs, that is, as part of a specific population that, in turn, lives within an ecological community.

So yeah biological populations are groups of individuals of the same species that share their habitat and that usually reproduce among themselves, a community is instead the set of populations of different species that share the same habitat. In other words, the sum of the populations of the same habitat forms a specific community, in which there are intra- and extra-species interactions that determine a trophic chain.

Population density

Population density
Population density is usually measured in individuals per unit area.

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 simply. This is usually measured in individuals per unit area, for example individuals per square kilometer, and is an average, an approximation to understanding how close individuals in a population are to each other.

Thus, when the population density is low, that is, few individuals per square kilometer, there will be a large area between one individual and another, making it more difficult to find them. However, when the population density is high, it will be easier to find an individual and they will be closer to each other, since there will be more in the same unit of space.

Population growth

Population growth is understood as increase or decrease in the total number of individuals in a population at a given time. Populations grow when the number of births (birth rate) exceeds the number of deaths (mortality rate), or when they receive migrations of individuals from other populations. And similarly, populations decrease when the number of deaths exceeds the number of births, or when a number of individuals migrate to some other population. In those cases in which the birth rate and the death rate are comparable, it will be said that it presents a growth equal to zero, that is, it neither increases nor decreases, it remains stable.

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