Population ecology is a field of ecology that deals with the dynamics of species populations and how these populations act together with the environment. In population ecology, density-dependent processes take place when population growth rates are synchronized by the density of a population.

Even though population ecology is a branch of biology, it makes available fascinating problems for mathematicians and statisticians who work in population dynamics.
The term population biology is frequently employed interchangeably with population ecology, even though ‘population biology’ is more commonly used when learning about diseases, viruses, and microbes, and ‘population ecology’ is made use of more regularly when studying plants and animals.
Population ecology is the branch of ecology that deals with the factors that influence the population size of a particular organism, population growth rate, and spatial dispersion of individuals with populations. Demography is the division of population ecology that deals with statistics associated to human populations.

Factors affecting population size

The factors that affect the population size are:
•The birth rates
•The death rates,
•Emigration, and
•Emigration.
Birth rates and immigration increase the number of individuals in a population while death rates and emigration reduce the number of individuals from a population. When additional individuals are being added to a population than the number that is being removed, it results to a population increase.
On the other hand, when the number of individuals that are being reduced from a population is more than the number that is being added to the population, it leads to a decrease in population size.
Population sizes would normally remain the same when the rate of individuals that are removed from it is equal to the rate of individuals that are added to it.
Such a population is said to be in a state of dynamic equilibrium.

Factors that affect population growth rates

Population growth rates are affected by relations between the abiotic and biotic environment. Climactic factors like precipitation and temperature can have great direct and indirect effects on population sizes.
Temporal rises and falls in abiotic conditions can be crucial causes of disparity in population sizes. Biotic factors like competition and predation can directly and indirectly influence population sizes.
Population dynamics can be affected by interactions with members of their own species (like intraspecific competition) and members of dissimilar species (like interspecific competition, predation, and mutualism).

Models of population growth

These are mathematical models developed by population ecologists to study the growth of populations. The simplest model of population growth is the exponential growth model which presupposes that the per capita growth rate -the change in population size/time/individual is constant.
Due to populations growing exponentially keep on growing at an increasing rate; the exponential growth model is not a practical model for the majority of populations.
The logistic growth model is a more practical model due to the fact that it permits the per capita growth rate to change with population size.
The carrying capacity, the population size at which the population growth rate equals zero, is attained when the per capita birth rate (# births/time/individual) is equal to the per capita death rate (# deaths/time/individual).
In logistic growth, birth and death rates are dependent on density; as population size increases, the per capita birth rate reduces (as a result of increased competition for resources) and the per capita death rate increases as a result of enlarged competition for resources, the increased multiplication of disease or an increase in predation that arises when predators are attracted to areas of lofty population sizes.
In the real world, patterns of population growth may be more complex than predicted by uncomplicated models due the fact that majority of populations are synchronized by a selection of density reliant (like competition and dispersal of disease) and density independent factors (like climate and disturbances).
Spatial dispersion
Individuals in a population may multiply across the environment in different patterns like clumped dispersion, smooth dispersion, or random dispersion. Interaction with both the abiotic and biotic environments can affect and determine the patterns of spatial dispersion.
For instance, clumped dispersions may occur when individuals are restricted to living in erratic with the suitable abiotic environmental conditions and smooth dispersions may arise as the result of intraspecific competition.

Human population growth

The study of human population growth is a particularly crucial subset of the field of population ecology.
Humans have had a distinctive pattern of population growth. Human demographers are concerned with the factors that cause patterns to differ between various countries and predicting what will occur to human population growth in the future

Ecological succession

Ecological succession is the pragmatic processes of change in the structure of species in an ecological community over time. Within any community a few species may become less abundant over some period of time, or they may even disappear from the ecosystem entirely.
In the same vein, over some time interval, some species within the community may become more plentiful, or fresh species may even occupy the community from nearby ecosystems.
This visible change over time in what is living in a specific ecosystem is “ecological succession”. There are two types of ecological succession- The primary succession and secondary succession.
Primary and secondary successions both produce a constantly altering mixture of species inside communities as disruptions of various intensities, sizes, and frequencies change the landscape. The chronological progression of species during succession, nevertheless, is not random.
At every stage particular species have developed life histories to utilize the particular conditions of the community. This situation compels a moderately expected sequence of alteration in the species composition of communities during succession.
At first only a small number of species from surrounding habitats are able to thrive in a disturbed habitat. As fresh plant species emerge, they change the habitat by altering things like the amount of shade on the ground or the mineral constitution of the soil.
These changes permit other species that are more suited to this modified habitat to replace the old species. These recent species are outmoded, in turn, yet by newer species.
A related succession of animal species occurs, and interactions between plants, animals, and environment affect the pattern and rate of succession change.
In a few environments, succession reaches a climax, which gives rise to a stable community subjugated by a small number of prominent species. This state of equilibrium known as the climax community, is thought to happen when the web of biotic interactions turn very complex that no other species can be allowed.
In a few environments, constant small-scale disruptions create communities that are a varied mixture of species, and any species may thrive.
Primary ecological succession is one of two types of biological and ecological succession of plant life, that occurs in an environment in which fresh substrate devoid of vegetation and normally lacking soil, like a lava flow or area left from drew back glacier, is deposited.
Primary succession can as well be defined as ecological succession that takes place in an opening of unoccupied, infertile habitat or that exists on an environment that is free of vegetation and normally lacking topsoil.
An example of primary succession is the original advancement of plant or animal communities in an area where no soil exists at the outset like a lava flow that results from volcanic eruption or rigorous landslide that enveloped the land.
The primary succession is essential in pioneering the area to create conditions that are favorable for the growth of other types of plants and animals.
Secondary succession takes place in areas where a community that beforehand existed has been removed; it is typified by smaller-scale disturbances that do not get rid of all life and nutrients from the environment.
Secondary succession is one among the two types of ecological succession of plant life. Secondary succession is the series of community alterations that occur on a formerly occupied, but distressed or smashed habitat.
Examples are areas which have been cleared of obtainable vegetation like after tree-felling in woodland and destructive events like fires.
Secondary succession is normally much swifter than primary succession for the following reasons:
•There is previously an existing seed bank of appropriate plants in the soil.
•Root systems uninterrupted in the soil, stumps and other plant parts from formerly existing plants can quickly rejuvenate and grow.
•The fertility and structure of the soil has also previously been adapted to a large extent by preceding organisms to make it more fit for growth and colonization.

Why ecological succession take place

Every living species has a group of environmental conditions under which it will thrive and reproduce most optimally.
In a particular ecosystem, and under that ecosystem’s range of environmental conditions, those species that can grow for the most part competently and produce the most viable children will become the majorly rich organisms.
Ecological succession may as well happen when the conditions of an environment unexpectedly and considerably alter. A forest fires, wind storms, and human activities such as agriculture all significantly change the conditions of an environment.
These considerable forces may as well wipe out species and consequently modify the dynamics of the ecological community triggering a mix up for dominance among the species still present.

Ecological succession on the Natural track

Succession is one of the main natural themes. It is possible to detect both the current process of succession and the effects of past succession events at roughly any point along the track.
The fluctuations of various species within our numerous communities exemplify both of the types of motive forces of succession: the collision of a well-known species to change a site’s ecological conditions, and the collision of large exterior forces to abruptly change the environmental nature of a site.
Some particular examples of visible succession are:
1.The growth of hardwood trees which includes ash, poplar and oak within the red pine planting area. The result of this hardwood tree growth is the increased shading and resultant mortality of the sun loving red pines by the shade tolerant hardwood seedlings.
The shaded forest floor situation created by the pines limits the growth of sun-loving pine seedlings and permits the growth of the hardwoods. The result of the growth of the hardwoods is the reduction and senescence of the pine forest.
2.The raspberry thickets growing in the sunny forest parts of the canopy produced by wind-thrown trees. Raspberry plants need sunlight to grow and thrive. Under the thick shade canopy principally of the red pines but as well under the dense stands of oaks, there is no adequate sunlight for the raspberry’s survival.
Nevertheless, in any place where there has been a tree fall, the raspberry canes have multiplied into impenetrable thickets.
How humans are are affected by ecological succession
Ecological succession is a power of nature. Ecosystems, due to the internal species changes and outdoor forces already mentioned, there are constant process of transformation and re-structuring.
To be pleased about how ecological succession affects humans and as well to begin to understand the inconceivable time and monetary cost of ecological succession, you only have to see a newly tilled garden plot.
Clearing the land for the garden and preparing the soil for planting showcases the main exterior event that radically re-structures and disrupts a previously existing ecosystem.