Population ecology is the subdivision of ecology that deals with the dynamics of populations of species and how these populations interact with the environment. It is the study of how population sizes of species change over time and space. The term is often used interchangeably with population biology or population dynamics. He also often describes the types of struggle for existence. Due to natural selection, the number of individuals that are maximally adapted increases.
In biology, a population is the degree of distribution of a particular species or a certain number of its representatives living in one area.
History
How did it all start? The development of population ecology is largely related to demography and current tables of life. This section is very important in the current environmental conditions.
Population ecology is important in conservation biology, especially whendeveloping a population viability analysis (PVA) that predicts the long-term likelihood of a species remaining in a given habitat. Although this ecology is a subspecies of biology, it presents interesting problems for mathematicians and statisticians who work in the field of population dynamics. In biology, population is one of the central terms.
Models
Like any science, ecology uses models. Simplified models of population change usually start with four key variables (four demographic processes), including death, birth, immigration and emigration. Mathematical models used to calculate changes in the demographic situation and population evolution assume the absence of external influence. Models can be more mathematically complex when “…several competing hypotheses collide with the data at the same time.”
Any model of population development can be used to mathematically derive certain properties of geometric populations. A population with geometrically increasing size is a population where breeding generations do not overlap. In each generation, there is an effective population size (and territory), denoted as Ne, which is the number of individuals in the population that can and will breed in any reproductive generation. What causes concern.
Selection theory r/K
An important concept in population ecology is the r/K selection theory. The first variable is r (internal rate of natural increasepopulation size, it does not depend on density), and the second variable is K (population carrying capacity, depends on density). Intraspecific relationships play a certain role in this.
R-selected species (e.g. many insect species such as aphids) is one that has high fecundity rates, low parental investment in juveniles, and high mortality rates before individuals reach maturity. Evolution promotes productivity in r-selected species. In contrast, K-selected species (such as humans) have low fertility rates, high levels of parental investment at a young age, and low mortality rates as individuals mature.
Evolution in K-selected species promotes efficiency in turning more resources into fewer offspring. As a result of unproductive interspecies relationships, these descendants may become extinct, becoming the last representatives of their population.
History of the theory
The r/K-selection terminology was coined by ecologists Robert MacArthur and E. O. Wilson in 1967 based on their work on island biogeography. This theory makes it possible to identify the causes of population fluctuations.
The theory was popular in the 1970s and 1980s when it was used as a heuristic device, but fell out of favor in the early 1990s when it was criticized by several empirical studies. The life history paradigm has replaced the r/K selection paradigm, but continues to include many of its important themes. The craving for reproduction is the maindriving force of evolution, so this theory is extremely useful for its study.
Thus, r-selected species are those that emphasize high growth rates, tend to exploit less crowded ecological niches, and produce many offspring, each of which has a relatively low probability of surviving to adulthood (i.e. high r, low K). A typical species of r is the dandelion (genus Taraxacum).
In unstable or unpredictable environments, r-selection prevails due to the ability to multiply rapidly. There is little advantage in adaptations that allow it to successfully compete with other organisms because the environment is likely to change again. Traits thought to characterize r-selection include: high fecundity, small body size, early onset of maturity, short generation time, and the ability to widely disperse offspring.
Organisms whose life history undergoes r-selection are often referred to as r-strategists. Organisms that exhibit r-selected traits can range from bacteria and diatoms to insects and grasses, as well as various seven-lobed cephalopods and small mammals, especially rodents. Differential theory K has an indirect connection with the natural selection of animals.
Selection of species
K-selected species exhibit traits associated with living in close to carrying capacity densities and tend to be strong competitors in crowded niches that invest more in lessthe number of offspring. Each of which has a relatively high probability of surviving to adulthood (i.e. low r, high k). In the scientific literature, r-selected species are sometimes referred to as "opportunistic", while K-selected species are described as "equilibrium".
In stable or predictable conditions, K-selection prevails, as the ability to successfully compete for limited resources is critical, and populations of K-selected organisms are usually very constant in numbers and close to the maximum that the environment can support. In contrast to r-selected, where the population size can change much faster. Low numbers lead to incest, which is one of the causes of mutations.
Characteristics
Traits thought to be characteristic of K-selection include large body size, long lifespan and the production of fewer offspring, which often require careful parental care until they are mature. Organisms whose life history is K-selected are often referred to as K-strategists or K-selected. Organisms with K-selected traits include large organisms such as elephants, humans, and whales, as well as smaller, longer-lived organisms such as arctic terns, parrots, and eagles. The increase in the population is one of the struggles for existence.
Classification of organisms
Although some organisms are identified primarily as r- or K-strategists, most organisms do not follow this pattern. For example, trees have traits such aslongevity and high competitiveness that characterize them as K-strategists. However, when breeding, trees usually produce thousands of offspring and disperse them widely, which is typical of r-strategists.
Similarly, reptiles such as sea turtles have both r- and k-characteristics: although sea turtles are large organisms with long lifespans (provided they reach adulthood), they produce a large the number of unnoticed offspring.
Other expressions
The r/K dichotomy can be re-expressed as a continuous spectrum using the economic concept of discounted future returns with r-choice corresponding to large discount rates and K-choice corresponding to small discount rates.
In areas with severe environmental disturbance or sterilization (eg after a major volcanic eruption, such as Krakatoa or Mount St. Helens), r- and K-strategists play different roles in the ecological sequence that restores the ecosystem. Due to their higher reproductive rates and ecological opportunism, the primary colonizers tend to be strategists and are followed by a string of growing competition between plant and animal life. The ability of the environment to increase energy content through photosynthetic capture of solar energy increases with increasing complex biodiversity as r-species proliferate to the maximum possible withusing strategies K.
New equilibrium
Eventually a new equilibrium (sometimes called a culminating community) ensues as r-strategists are gradually replaced by K-strategists who are more competitive and better adapted to emerging microecological landscape changes. Traditionally, biodiversity was considered to be maximized at this stage with the introduction of new species, resulting in the replacement and local extinction of endemic species. However, the intermediate disturbance hypothesis states that intermediate levels of disturbance in the landscape create patches at different levels of succession, facilitating the coexistence of colonizers and competitors on a regional scale.
Although generally applied at the species level, r/K selection theory is also useful for studying the evolution of ecological and life differences between subspecies. For example, the African honey bee A. m. scutellata and the Italian bee A. m. ligustica. At the other end of the scale, it has also been used to study the evolutionary ecology of entire groups of organisms such as bacteriophages.
Research opinions
Some researchers such as Lee Ellis, J. Philip Rushton, and Aurelio Jose Figueredo have applied r/K selection theory to various human behaviors, including delinquency, sexual promiscuity, fertility, and other traits related to life history theory. Rushton's work led him to develop the "differential K theory" to try to explain the many differences in human behavior across geographic areas. And this theory has been criticized by many other researchers. The latter suggested that the evolution of human inflammatory responses is related to the choice of r/K.
Although the r/K selection theory began to be widely used in the 1970s, it also began to receive increasing attention. In particular, a review by environmentalist Stephen S. Stearns drew attention to gaps in theory and to ambiguities in interpreting the empirical evidence to test it.
Further research
In 1981, Parry's 1981 review of the literature on r/K selection showed that there was no agreement among researchers using the theory of defining r- and K-selection, leading him to question the assumption of a relationship between reproductive costs. function.
A study by Templeton and Johnson in 1982 showed that in a population of Drosophila mercatorum (a subspecies of the fly) subjected to K-selection, it actually produces a higher frequency of traits typically associated with r-selection. Several other studies contradicting the predictions of r/K selection theory were also published between 1977 and 1994.
When Stearns reviewed the status of theory in 1992, he noted that from 1977 to 1982, the BIOSIS literature search service averaged 42 theory citations per year, but from 1984 to 1989 the average dropped to 16 per year. year and continued to decline. He concluded that the r/K theory was once a useful heuristic that no longer serves a purpose in life history theory.
Most recently the panarchy theory of adaptiveabilities and resilience promoted by S. S. Holling and Lance Gunderson have revived interest in theory and are using it as a way to integrate social systems, economics and ecology.
Metapopulation ecology
Metapopulation ecology is a simplified model of the landscape into areas of different quality levels. Migrants moving between sites are structured in metapopulations as sources or sinks. In metapopulation terminology, there are emigrants (individuals who leave the site) and immigrants (individuals who move into the site).
Metapopulation models examine site dynamics over time to answer questions about spatial and demographic ecology. An important concept in metapopulation ecology is the rescue effect, in which small patches of lower quality (i.e. sinks) are maintained by a seasonal influx of new immigrants.
The structure of the metapopulation evolves from year to year, where some sites are sinks, such as dry years, and become springs when conditions are more favorable. Ecologists use a mixture of computer models and field studies to explain metapopulation structure. The age structure of a population is the presence of representatives of certain ages in a population.
Autoecology
The older term autoecology (from Greek: αὐτο, auto, "self"; οίκος, oikos, "household" and λόγος, logos, "knowledge"), refersroughly in the same field of study as the ecology of the population. It follows from the division of ecology into autecology - the study of individual species in relation to the environment - and synecology - the study of groups of organisms in relation to the environment - or community ecology. Odum (an American biologist) believed that synecology should be divided into population ecology, community ecology, and ecosystem ecology, defining autoecology as "species ecology".
However, for some time biologists have recognized that the larger level of organization of a species is the population, because at this level the species gene pool is most consistent. In fact, Odum considered "autoecology" as a "current trend" in ecology (i.e., an archaic term), although he included "species ecology" as one of the four divisions of ecology.
The first publication of Population Ecology (originally called Population Ecology Research) was released in 1952.
Research papers on population ecology can also be found in animal ecology journals.
Population dynamics
Population dynamics is a branch of the life sciences that studies the size and age composition of populations as dynamic systems, and the biological and environmental processes that drive them (for example, birth and death rates, and immigration and emigration). Examples of scenarios are population aging, growth or contraction.
Exponential growth describes unregulated reproduction. This is very unusual to see in nature. Population growth has been exponential over the past 100 years.
Thomas M althus believed that population growth would lead to overpopulation and starvation due to lack of resources, including food. In the future, people will not be able to feed large populations. The biological assumption of exponential growth is that the per capita growth rate is constant. Growth is not limited to resource scarcity or predation.
Population dynamics has been widely used in several applications of control theory. Using evolutionary game theory, population games are widely applied to various industrial and everyday contexts. Mainly used in multiple input, multiple output (MIMO) systems, although they can be adapted for use in single input, single output (SISO) systems. Some application examples are military campaigns, distribution of resources for water distribution, dispatch of distributed generators, laboratory experiments, transportation problems, communication problems. In addition, with adequate contextualization of production problems, population dynamics can be an effective and easy-to-apply solution to control problems. Numerous scientific studies have been and are ongoing.
Overpopulation
Overpopulation occurs when the population of a species exceeds the carrying capacity of an ecological niche. This may be the resultincrease in birth rate (fertility rate), decrease in mortality rate, increase in immigration or unsustainable biome and depletion of resources. Moreover, this means that if there are too many people in one habitat, people limit the resources available to survive. The age structure of the population does not play a special role.
In the wild, overpopulation often causes predator populations to rise. This has the effect of controlling the prey population and ensuring that it evolves in favor of genetic characteristics that make it less vulnerable to predators (and the predator can co-evolve).
In the absence of predators, species are bound by the resources they can find in their environment, but this does not necessarily control overpopulation. At least in the short term. An abundant supply of resources can lead to a population boom followed by a population crisis. Rodents such as lemmings and voles have these cycles of rapid population growth and subsequent decline. Populations of snowshoe hares also change dramatically cyclically, as does one of the predators that hunt them, the lynx. Tracking this trend is much easier than identifying the genome of a population.
