POPULATION DYNAMICS: CONCEPTS, IMPORTANCE, EXAMPLES - BIOLOGY - 2025

The population dynamics or population includes the study of all the variations experienced by a group of individuals of the same species. These changes are measured in terms of variability of parameters such as number of individuals, population growth, social and age structure, among others.

Population dynamics is one of the central themes of ecological science. By studying this branch, the bases that govern the existence and permanence of living organisms can be established. In addition to taking into account the relationships they have (intra and interspecific).

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Definition of population

One of the basic concepts in ecology is the biological population. This is defined as a consistent group of organisms of the same species that coexist in the same time and space (they are sympatric), with the possibility of interbreeding between the individuals that live there.

The organisms that are part of the population form a functional unit, thanks to all the interrelationships that develop there.

Concepts that govern the study of populations

Population growth models

Population growth is studied using mathematical models, and there are different types depending on the amount of resources that exist in the population.

Exponential growth

The first model is exponential growth. This model assumes that there are no interactions with other species. In addition, it also involves the unlimited existence of resources and there is no restriction on the population.

As is logical to think, this model is exclusively theoretical since there is no natural population that fulfills all the aforementioned assumptions. The model allows estimating the population size at a given time.

Density-dependent growth

The next model used is called density-dependent or logistic growth. This variation includes more realistic conditions, such as limited resources.

The population begins to grow as in the previous model but reaches a certain point where it depletes its resources and the reproductive rate decreases.

Thus, small populations tend to have a higher growth rate due to the greater availability of resources and spaces - the model is initially exponential. As time passes, resources run out and the per capita increase decreases.

Graphically, the second model is a sigmoid curve (S-shaped) that has an upper limit called K. This value corresponds to the load capacity or the maximum density that it can withstand in that medium.

In some populations, toxic wastes produced by the same individuals cause growth inhibition.

Late logistics growth

This model has been the most accepted by researchers because it seems to better fit the reality of population dynamics.

It shows rapid growth, where the speed of resource depletion is just as fast. This phenomenon leads to a collapse, where it falls and grows again.

In other words, growth is evidenced as cycles of density in time, since there are repetitive events of decrease and increase of individuals.

Growth with cooperation

There is a specific model to be applied to certain species with gregarious behaviors, such as bees, humans, lions, among others. In this model, the individual obtains a benefit when he performs an act of cooperation with his peers.

The behavior is not random, and the benefit of cooperation is associated with close relatives and relatives, in order to favor their “same genes”.

Interactions between species

Individuals in each population are not isolated from each other. Each one establishes different types of interactions with members of the same species or with members of another species.

Competition is a phenomenon with extremely important ecological implications. It is an important force that drives various evolutionary processes, such as speciation. We have several examples of negative interactions, such as predator-prey or plant-herbivore.

Two species cannot compete forever, if they use very similar resources, one may displace the other or they may separate in the use of some resource.

However, not all interactions are of the negative kind. There may be relationships that benefit both parties (mutualism) or that only one is benefited and the other is not affected (commensalism).

Importance

Conservation

In order to establish an effective conservation plan, it is necessary to have all the necessary information on the population in danger. Researchers should put the aforementioned methodologies into practice before implementing the conservation method.

In addition, knowing what population growth is like helps us understand the effect of human activities on species. For example, if we want to measure the effect of a construction, we measure the population size and other parameters in the population of interest before and after the intervention.

Management of biological resources

Many of our resources depend directly or indirectly on the growth and population dynamics of a certain species. Fishing represents an important source of food for certain human populations, particularly those that inhabit regions near the coast.

Knowledge of how the population varies is essential to maintain and ensure a balanced food intake. In the event that there is evidence of a decrease in the population number, appropriate measures must be taken to avoid the local extinction of the population.

Simulations on human populations

Different researchers (like Meadows in 1981, for example) have used different models of population growth to interpret and predict the future behavior of human populations.

All this in order to formulate advice and recommendations to avoid mortality due to a possible overpopulation.

Applications in the medical field

The populations of pathogens that inhabit humans can be studied from the ecological point of view, to specify behaviors that can help to understand the disease.

In the same way, it is necessary to know the population dynamics of vectors that carry diseases.

Examples

In 2004, an investigation was carried out that aimed to study the population dynamics Lutjanus argentiventris in the Gorgona National Natural Park, Colombia. To meet this objective, individuals were fished for almost 3 years in the study area.

The animals were measured and the sex ratio (1: 1.2), birth rate and mortality were evaluated.

The growth parameters were evaluated, and how they affected the climatic phenomena of La Niña and El Niño. In addition, population growth was determined using Von Bertalanffy mathematical models.

Individuals were found to be more abundant in May and September and in 2000 they suffered a population decline.

References

1. Hannan, MT, & Freeman, J. (1977). The population ecology of organizations. American journal of sociology, 82 (5), 929-964.
2. Parga, ME, & Romero, RC (2013). Ecology: impact of current environmental problems on health and the environment. Ecoe Editions.
3. Ramírez González, A. (2017). Applied ecology: Design and statistical analysis. University of Bogotá Jorge Tadeo Lozano.
4. Reece, JB, Urry, LA, Cain, ML, Wasserman, SA, Minorsky, PV, & Jackson, RB (2014). Campbell Biology. Pearson.
5. Rockwood, LL (2015). Introduction to population ecology. John Wiley & Sons.
6. Rojas, PA, Gutiérrez, CF, Puentes, V., Villa, AA, & Rubio, EA (2004). Aspects of the biology and population dynamics of the yellow-tailed snapper Lutjanus argentiventris in Gorgona National Natural Park, Colombia. Marine Research, 32 (2), 23-36.