What is the difference between density-dependent and density independent factors give examples of each?

Population refers to the group of the organism of the same species living at the same time in the same area where the size, density, and growth of it are considered for regulation and limitation.

Its growth is being carefully watched and studied by every nation around the world because any change in the number of inhabitants can have a large effect on the economy of the country.

Two important factors regulate the growth or decline of the population and they are Density Dependent and Density Independent factors.

Density Dependent vs Density Independent

The difference between Density Dependent and Density Independent is that Density Dependent regulates the population in proportion to its density whereas Density Independent regulates the population without considering its density.

Density Dependent is responsible for regulating the population in proportion to its density such as prediction, competition, or disease. It generally causes the population to either decrease or increases depending on how it affects the ecosystem and operates in a large population.

Density Independent are those that regulate the population without considering its density such as natural disasters and the weather. The measurement of population control operates small as well as large populations and is not bored on density.

Natural disasters such as storms, drought, floods, extreme temperature, fire, and distinction of organisms can cause a decrease in their population.

Comparison Table

What is Density Dependent?

Density Dependent is one of the factors/measures of regulating population growth considering the density of the population such as prediction, competition, and disease. Its regulation can be affected by the factors that affect the birth and death rate such as competition and predation.

It can also be affected by other factors such as abiotic factors and environmental factors such as uncertain weather and conditions such as a fire. In ecology, density-dependent factors are also known as regulating factors.

Any force that affects the size of a population of living things which often arises from biological phenomena, rather than chemical or physical phenomena. It is called regulating factors because they maintain population density within the narrow range of value.

Some diseases spread faster, in a population where individuals live near each other rather than who lives apart. Therefore, the density of that particular population decreases, through mortality or migration, decreasing the influence of density-dependent factors.

The liveliness of most population of living things are influenced by a combination of factors of density-dependent and the relative effect of the factors vary among the population of all kind of living organism.

What is Density Independent?

Any factor that affects the size of a population of living things regardless of the density of the population which often arises from chemical and physical phenomena is known as density Independent. It is also called a limiting force in ecology.

Disasters such as floods, famine, landslides, climate change, wildfire affect a population of living creatures whether individuals are clustered close together or spread far apart. Most of the living organisms breathe oxygen, oxygen availability is a density-independent factor.

Therefore, if oxygen concentration declines or breathable oxygen suddenly made unavailable then those organisms perish and the population of the various affected organisms will decline.

Pollutants contribute essentially to environmental stress, restricting the growth rates of populations. Every species including amphibians has specific tolerances for environmental toxins and is particularly susceptible to environmental pollutants.

Since Endocrine-disrupting toxins can control the growth of amphibians, it results in restriction of population growth irrespective of the size of the amphibian population. Apart from pesticides, these also include herbicides, fungicides, thermal pollution and heavy metal contaminations, etc.

The liveliness of most populations of living beings is influenced by a combination of factors of density independence and the relative importance of these factors varies from species to species and from population to population.

Main Differences Between Density Dependent and Density Independent

1. Density Dependent is responsible for regulating the population in proportion to its density such as prediction, competition, or disease. On the other hand, Density Independent are those that regulate the population without considering factors like weather and natural disasters.
2. Density-dependent generally operates in a large population. As against, Density Independent operates in both Small and large populations.
3. Density-dependent depends upon the gain and loss rate. Whereas, Density Independent acts on their own.
4. The factors of Density-dependent are food, shelter, prediction, competition, and disease. On the other hand, The factors of Density Independent are flood, fire, drought, extreme temperature, and tornados.

References

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The number of individuals in a population will increase and decrease due to natural and human factors. Natural fluctuations in population size occur due to factors such as food availability and the number of predators.

Humans can cause population sizes to change by introducing invasive species, hunting or changing the environment. A healthy ecosystem, with high biodiversity is important in helping reduce the effects of these factors on a particular species.

Factors affecting species populations

Species populations of Galapagos fluctuate due to natural and human factors. Species population growth or decline can be caused by either density-dependent or density-independent factors:

• Density-dependent factors have varying impacts according to population size. Different species populations in the same ecosystem will be affected differently. Factors include: food availability, predator density and disease risk.
• Density-independent factors are not influenced by a species population size. All species populations in the same ecosystem will be similarly affected, regardless of population size. Factors include: weather, climate and natural disasters.

Biodiversity and population health

High biodiversity can help to stabilise an ecosystem and reduce the overall impact of density-dependent and density-independent factors. Biodiversity is a measure of the difference between the living organisms within an ecosystem.

With many endemic species and a great range of wildlife, Galapagos has a high level of biodiversity. This is due to the number of very different habitat zones found in Galapagos, and also due to more acute environmental differences between the habitats of each island.

Biodiversity is an important factor in ensuring a healthy ecosystem. For example, an ecosystem with a wide range of producers will provide the primary consumers with a stable and varied food supply. Each species also plays a unique role in servicing the ecosystem, ensuring that it operates smoothly. Ecosystems with a high level of biodiversity are more able to recover from disasters, whether natural or man-made (anthropogenic).

A fluctuation in the size of one species population can impact on other species within the ecosystem. A species that will have a large impact on the ecosystem is known as a keystone species. The more biodiverse an ecosystem, the less vulnerable it will be to fluctuation in keystone species populations.

Case study: Galapagos giant tortoise

A Galapagos giant tortoise munching on some greenery in Santa Cruz © Catherine Rouse

The Galapagos giant tortoise is a keystone species and its population has declined as a result of human activity. During the 18th and 19th centuries, whaling ships would stop at the Galapagos Islands and hunt giant tortoises to feed their crew.

Giant tortoises continued to be targeted as the Islands’ settlements expanded and the human demand for food increased. Their population was estimated to be around 250,000 in the 1500s, when they were first discovered. However, a 1974 census recorded just 3,060. Research suggests that 13,000 giant tortoises were taken from the Islands between 1831 and 1868 by whaling crews.

The decline of the Galapagos giant tortoise population impacted on Galapagos ecosystems. Even plant and animal species directly unaffected by human activity began to experience great population change.

Galapagos giant tortoises shape their habitats by grazing on plants, dispersing plant seeds and trampling areas of vegetation. They therefore play an important role in germinating seeds, as well as in thinning out and opening up new areas of ground for different types of vegetation to grow.

Without the giant tortoises constantly changing the environment, a few fast-growing plant species could dominate a much less biodiverse ecosystem.

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