Population Ecology


The word ‘population’ is derived from the Latin “Populus” which means people. Ecology gives the simple definition of population as a group of organisms belonging to the same species and living in the same area at the same time.

The last and final component of the population is an individual organism that interbreeds to produce more offspring alike them. Populations are further categorized into demes and local populations.

According to some ecologists, populations are of the following two types: Monospecific population, the one having organisms of only one species. And polyspecific population is the one having mixed populations i.e., populations are from more than one species.

Sometimes polyspecific is regarded as a community.

Definition of Population Ecology

In population biology, the term population describes a group of members of a species living in the same area. The definition of population ecology is the study of how different elements impact population growth, rates of survival and reproduction, and risk of extinction.

Population ecology has its inmost historical roots, and its wealthiest advancement, in the study of population growth, regulation, and dynamics, or demography. Human population growth functions as a crucial design for population ecologists and is one of the most essential environmental concerns of the twenty-first century.

However, all populations, from diseased organisms to wild-harvested fish stocks and forest trees to the species in a successional series to laboratory fruit files and paramecia, have actually been the topic of standard and applied population biology.

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Characteristics of Population Ecology

Ecologists utilize various terms when understanding and discussing populations of organisms. A population is all of one sort of species residing in a specific location.

1.Population Size and Density

The study of any population typically starts by figuring out the number of individuals of a particular species that exist, and how carefully associated they are with each other. Within a specific habitat, a population can be characterized by its population size (N), the overall number of individuals, and its population density, the number of individuals within a specific location or volume.

Population size and density are the two primary characteristics used to describe and understand populations. For example, populations with more individuals might be more stable than smaller populations based on their genetic variability, and thus their perspective to adjust to the environment. Alternatively, a member of a population with low population density (more expanded in the habitat), might have more problems discovering a mate to reproduce compared to a population of greater density.

2.Population dispersion or spatial distribution

Dispersion is the spatial pattern of individuals in a population relative to one another. In nature, due to various biotic interactions and the influence of abiotic elements, the following three standard population circulations can be observed:

(a) Regular dispersion:

Here the individuals are basically spaced at an equivalent distance from one another. This is uncommon in nature but in common is cropland. Animals with territorial behavior tend towards this dispersion.

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(b) Random dispersion:

Here the position of one individual is unrelated to the positions of its neighbors. This is also relatively uncommon in nature.

(c) Clumped dispersion:

The majority of populations display this dispersion to some extent, with individuals aggregated into patches interspersed with no or few individuals. Such aggregations may result from social aggregations, such as family groups or might be because of particular patches of the environment being more favorable for the population concerned.

3.Age structure

In a lot of kinds of populations, individuals are of different ages. The proportion of individuals in each age group is called age structure of that population. The ratio of the various age groups in a population figures out the existing reproductive status of the population, thus predicting its future. From an environmental viewpoint, there are three significant ecological ages in any population.

Age pyramid:

The model representing geometrically the proportions of different age groups in the population of any organism is called age pyramid. According to Bodenheimer (1938), there are following three standard kinds of age pyramids.


(a) A pyramid with a broad base (or triangular structure):

It shows a high percentage of young individuals. In rapidly growing young populations birth rate is high and population growth might be rapid.

(b) Bell-Shaped Polygon:

It shows a fixed population having an equal number of young and middle-aged individuals. As the growth rate becomes slow and steady, i.e., the pre-reproductive and reproductive age groups become basically equivalent in size, the post-reproductive group remaining as the smallest.

(c) An urn-shaped structure:

It suggests a low percentage of young individuals and shows a declining population. Such an un-shaped figure is obtained when the birth rate is considerably minimized the pre-reproductive group decreases in proportion to the other two ages of the population.

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Population Growth Rate

Population growth reflects the change in the number of individuals over a time period. The population growth rate is impacted by birth and death rates, which in turn belong to resources in their environment or outdoors aspects such as climate change and disasters.

Carrying capacity

Due to the fact that the real world does not use endless resources, the variety of individuals in a growing population eventually will reach a point when resources become scarcer. Then the growth rate will slow and level off.

As soon as a population reaches this leveling-off point, it is thought about the best population the environment can sustain. The term for this phenomenon is carrying capacity. The letter K represents carrying capacity.

Population cycles

Populations fluctuate in a cyclic way depending on the resources and competitors in the environment. An example would be harbor seals, affected by pollution and overfishing. Decreased prey for the seals causes increased death of seals. If the number of births was to increase, that population size would remain stable. However, if their deaths outpaced births, the population would decrease.

As environment change continues to impact natural populations, using population biology designs ends up being more vital. The many elements of population ecology help researchers better understand how organisms interact and help in techniques for species management, conservation, and protection.