If we think about nature itself and all the living beings that inhabit it, there is a great network of interactions both between species and between species with their environment. In order to study these very complex interactions, it is first necessary to study the populations separately, this is thanks to population ecology or demoecology. Once we know the structure and dynamics of populations, we can go one step further and study that extremely complex network that we mentioned earlier.
What is population ecology or demoecology
The definition of ecology has undergone many modifications over the years, but perhaps the most complete is that given by Margalef in 1978, which defines ecology as “the science that studies systems at a level at which complete organisms ( or individuals) can be considered elements of interaction, both between them and with the environmental matrix. ” Learn more about this science with these other Green Ecology articles on the Definition of Ecology , the History of Ecology and What is Ecology and its Difference from Ecology .
Therefore, knowing this definition, population ecology is nothing other than that branch of ecology that is dedicated to the study of populations , taking into account their dynamics and structure. Learn more about this and other branches of this science in this other post on What are the branches of ecology and what each one studies .
When we speak of population in ecology we refer to all those individuals that belong to the same species and that occupy a certain geographic region in the same period of time. The individuals that are part of a population are ecologically the same: the life cycle they present is the same, all their processes and the way in which they interact with the environment and, in addition, there is an exchange of genetic information between them.
To better understand the populations, it is also necessary to study their behavior with the environment and the rest of the species. There are different types of populations :
- Family populations: are those that are related to each other. Wolf packs or even the human family are examples of this type of population.
- Gregarious populations: are those that go together for reasons of mobilization such as migration or to get food, they do not have to be related. This happens for example in schools of fish.
- Social populations : they are hierarchical populations that work in an organized manner since it would be difficult for them to survive if they were independent. A very clear example of this type of population is seen in bees.
- Colonial populations: formed by those individuals that reproduce by asexual reproduction, that is, they all start from the same parent. These stay together forever. An example are corals, bacteria, algae, among others.
For the study of populations in ecology , different characteristics and processes are taken into account:
- Size: refers to the number of individuals in the population.
- Density: this property refers to the number of individuals of a species that occupies a surface or volume in a given time.
- Demographic parameters: they are the birth rate, death rate, immigration rate and emigration rate. These parameters are those that change in the number of individuals in the populations as time passes.
- Birth rate: are those individuals who are born per unit of time.
- Mortality rate: are those individuals who die per unit of time.
- Immigration rate: individuals of the same species that come from another habitat and new ones enter the population.
- Emigration rate: are those individuals that leave the population as they move to another habitat.
- Population growth rate: this is only the result of the number of individuals that each moment, after having analyzed each of the demographic parameters. Models are used to represent population growth, the simplest and most well-known is the exponential growth model.
- Distribution pattern: indicates how the individuals of the population are arranged in the territory they occupy, for example, they can be found grouped, randomly or uniformly.
- Population structure: this property takes into account the sex of the individual, its size or its age.
Population example in ecology
We will give the example of a population of pigeons found in a park, it is made up of 35 pigeons of which 21 are female and 14 are male, they weigh approximately 0.32 kg and are about 32 cm long. They are usually grouped or uniform. This species has an exponential growth, since in some areas it is even considered a pest and invades the habitat of other species.
In the natural environment everything is in one way or another related, since we are talking about an open system. We have explained that population ecology is the science that studies both the structure and the dynamics of populations. The community ecology is something similar, but this study the structure and dynamics among different populations that coexist in the same habitat at the same time. So, a community is one formed by populations of different species that interact with each other and the environment in which they live. Therefore, the members of a community or biocenosis and the physical environment where the relationships between them take place ( biotope) would be the components that make up the biological system called the ecosystem.