Population Limiting Factors

11 Key excerpts on "Population Limiting Factors"

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  The Blue Planet

  An Introduction to Earth System Science

  • Brian J. Skinner, Barbara W. Murck(Authors)
  • 2011(Publication Date)
  • Wiley

    (Publisher)

  Make the CONNECTION Think of a natural population, such as a population of insects, or bears, or bacteria, or dandelions. How many things can you list that might limit the growth of this population? Identify whether these limitations come from the hydrosphere, atmosphere, geosphere, biosphere, or anthroposphere. Anything that acts to control or cap population growth is called a limiting factor. In Chapter 15 we discussed the role of essential nutrients as limiting factors to biological productivity and to the growth of individual organisms, but chemical nutrients are not the only resources that can be limiting to population growth. For example, on the ground floor of a densely veg- etated rain forest, light could be a factor that limits growth or survival. In a desert, water is usually the most important limiting factor. For pandas, which eat only bamboo, the avail- ability of bamboo forest habitat is a limiting factor. For snowshoe hares, an abundance of lynx—an important predator—might be a limiting factor; and so on. All of these factors—limitations to food, water, space, or light; barriers to reproductive success; competition, predation, disease; cli- mate change; and many other environmental limitations and risk factors, both intrinsic and extrinsic—provide resistance to unlimited growth in populations. In other words, they prevent population growth from following an infinite exponential growth trajectory, limiting it instead to following a logistic growth curve. Carrying Capacity The leveling-off point of the logistic curve in Figure 16.3 represents the influence of limits, both intrinsic and extrinsic, on population growth. It also provides a theoretical maximum number of individuals in a population that can be supported by that particular ecosystem. This number is called the carrying capacity, denoted by the letter K. Carrying capacity is an important concept both for populations and for the ecosystems that support them.

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  Ecology

  Principles and Applications

  • J. L. Chapman, M. J. Reiss(Authors)
  • 1998(Publication Date)
  • Cambridge University Press

    (Publisher)

  Figure 5.3b is the rate of change of population growth with population size. The environmental factors which are responsible for regulating populations are often the ones that affect the growth of the individual. This is because populations are made up of individuals. Population increase depends on the reproductive fitness and life span of these individuals. Factors such as energy and nutrient availability, flood, drought, predators and disease will all affect population size. Environmental factors can affect populations in various ways depending on whether the factor is variable or not, and how predictable the variation is. It is worth classifying these environmental factors here so they can be borne in mind for the rest of the section. Constantly limiting factors These are always in short supply, but are relatively constant so that a population is limited to a certain fairly constant size by the factor. Individuals may have to compete for the resource. For example, plants compete for space and light, birds for nesting territories and many heterotrophs for food. These factors do not usually produce large changes in population. Variably limiting factors These are variable but predictable, like seasonal drought and cold, or variation in food availability. They are only an influence at certain times of year when they may cause the population to crash. Some species avoid such factors by taking evasive action. For example, some birds migrate and deciduous trees drop their leaves. Unpredictable factors These change in an irregular way so population dynamics may vary considerably over time. Unpredictable factors include weather effects, grazing or predation pressure and disease levels. Unpredictable factors tend to alter population size in a fairly haphazard way: a volcanic eruption, fire, or virulent disease epidemic may kill most, or even all of a population.

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  Introduction to the Fishery Sciences

  • William F. Royce(Author)
  • 2013(Publication Date)
  • Academic Press

    (Publisher)

  Each species has its own set of limiting factors. An aquatic species is limited by temperature, salinity, depth, light, dissolved oxygen, and prob-ably by any of many other factors. Many of the elements present in minute quantities, poisons excreted by certain algae, interactions with virus or bacteria have been shown to be limiting. Anything in the environment that affects the physiology of an organism may be at some level a limiting factor for that organism. The limiting factors operate according to their strength or level in complex ways. Most physical and chemical factors have maximum and minimum limits. Some factors may operate only at certain times, others continuously. Usually, one factor will be more critical than others and will be the con-trolling factor. Among required chemical factors the controlling factor will be the one available in the smallest fraction of the amount needed. This is called Liebig's law of the minimum and has been extended in an abstract sense to physical and biological factors. The reproductive period is commonly the time of least tolerance. The conditions must be tolerable by spawning animals, eggs, larvae, and young which frequently have different needs. For example, the Pacific oyster requires a minimum temperature for successful spawning but will grow and fatten perfectly well at much lower temperatures. This limiting factor is overcome in oyster culture by collection of the young in spawning areas and their transfer to growing areas. The determination of tolerance levels is important in understanding the distribution of organisms and is receiving increasing attention as man changes the environment. With many chemical and physical factors, toler-ance is a function of both level and time; the greater the change from the ideal level, the less the length of time the change will be tolerated.

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  Laws, Theories, and Patterns in Ecology

  • WALTER DODDS(Author)
  • 2009(Publication Date)
  • University of California Press

    (Publisher)

  Limits were pointed out by Aristotle 2,300 years ago (Krebs 1988). Most organisms can use only part of the world, inhabit restricted areas, and have defined resource use patterns. The specific factor that will limit population growth and size is a more difficult problem and is one of the primary pre-dictive constraints with this law. Resource supply, competition (in-terspecific or intraspecific), or predation (including disease) can ultimately limit reproduction. Population density dependence is a common feature of species population time series (Brook and Bradshaw 2006). This law does not mean that the logistic curve will necessarily describe the population trajectory. There is no fundamental law or property that dictates the mathematical structure of the logistic curve, but the logistic is a simple mathe-matical way to include density dependence in a continuous equa-tion (Rose 1987). Time lags and fluctuations in carrying capacity and growth rates are all possible and make it difficult to predict Laws / 37 exactly when population level will be limited. Still, if rate of supply of a limiting resource is known, the final population that can be supported can be calculated. Our inability to calculate a human carrying capacity (Cohen 1995) exemplifies difficulties faced by ecologists in determining limits to growth. Inability of Homo sapiens to control their global environmental effects is symptomatic of their inability to comprehend the reality of this law. This law applies at the population scale. The self-thinning rule (or law) in plants is based on space-filling models of how much biomass can develop per unit area (Pretzsch 2002), and the limitation is photon flux density. Self-thinning is simply a func-tion of efficiency of use of sunlight, and amount of sunlight per unit area dictates the population density that is possible. This ef-ficiency varies among species, so the “rule” leads to somewhat variable scaling relationships (Pretzsch 2006).

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  Ecology and Applied Environmental Science

  • Kimon Hadjibiros(Author)
  • 2013(Publication Date)
  • CRC Press

    (Publisher)

  The adoption of the biotope concept gives an existing and expanding use of the term. The growth of a population is affected both by its internal forces and external factors. As a rule, the population has an internal tendency to increase with a fixed rate per individual, which initially leads to an expo-nential change. However, the rate of increase is usually halted under the influence of abiotic environmental factors such as temperature, radiation, humidity, nutrients etc. or biotic environmental factors such as simple or complex population interactions within the ecosystem. One of these factors emerges in each case as the limiting factor. A population’s size change in time basically depends on three parameters: • Natality rate • Mortality rate • Immigration rates of individuals to and from the population The examination of temporal change within animal and plant popula-tions, as well as that of the human population, has always been of vast practical importance. That is why many mathematical methods of study, mainly of empirical/statistical character, were developed a long time ago in order to assess these phenomena; these methods belong to population dynamics and demography. 3.1.1 Age Distribution Each population can be subdivided into age groups. All the individuals of a population whose age lies within a specific age span belong to the corresponding group. For example, from 100 individuals of a human popu-lation, 20 may be children (0–15 years), 15 may be youngsters (15–25), 40 mature (25–60) and 25 elderly (over 60) (Figures 3.1, 3.2 and 3.3). Characteristic age distributions of human populations are shown in Figure 3.4. Organisation at Population Level 17 © 2010 Taylor & Francis Group, LLC 0 4 8 1 2 16 Age (months) 60 50 40 30 20 10 Population (%) Figure 3.1 Age distribution of a population with high natality rate.

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  Ecology and Management of Inland Waters

  A Californian Perspective with Global Applications

  • Marc Los Huertos(Author)
  • 2020(Publication Date)
  • Elsevier

    (Publisher)

  Whereas competition may influence population dynamics, exclude weaker competitors, and promote niche differentiation, we also recognize that numerous other types of species interactions occur in streams, lakes, wetlands, etc. Predation, cannibalism, disease, and parasitism are commonly observed factors that affect population dynamics.

  After reading this chapter, you should be able to

  1. 1.  Use predator–prey equations to evaluate the role of trophic interactions to predict population dynamics;
  2. 2.  Summarize how sexual selection can influence population dynamics, e.g., predator/prey and infection vector and host;
  3. 3.  Describe succession and how communities change with time;
  4. 4.  Evaluate various lotic and lentic systems using energy transfer and nutrient flux in ecosystems.

  Environment: Biotic Factors

  Types of Species Interactions

  Whereas the common use of the word “environment” refers to everything around us, ecologists identify two broad environmental factors: 1) abiotic factors: the physical and chemical factors, and 2) biotic factors: interacting organisms. When evaluating an area, we analyze a combination of abiotic and biotic factors to better understand the patterns and processes in ecological systems. The biotic factors include numerous types of interactions, including competition, discussed in Chapter 4 . Although inter- and intraspecific competition may play an important role in population growth, other asymmetric interactions also structure communities in visible and dramatic ways (Table 5.1 ).

  Table 5.1 Type of asymmetric interactions between two species.

  Interaction	Effect of Sp. 1 on Sp. 2	Effect of Sp. 2 on Sp. 1
  Exploitation	Positive	Negative
  Competition	Negative	Negative
  Mutualism	Positive	Positive
  Commensalism	None	Positive
  Amensalism	None	Negative
  Nuetralism	None	None

  Extending Population Biology

  Primary Production and Herbivory

  Periphyton is a combination of algae and bacteria that grow on stream bottom substrates. The growth of the algae is not only controlled by the competition for light and nutrients, but also by herbivory. Herbivory is a type of exploitation as it reduces algae (or plant) biomass, but have other effects too, e.g., increasing the diversity of the algae species, increasing productivity by reducing self-shading, and stimulating growth by releasing nutrients. But these changes can also depend on the herbivore species.

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  Biology 2e

  • Mary Ann Clark, Jung Choi, Matthew Douglas(Authors)
  • 2018(Publication Date)
  • Openstax

    (Publisher)

  Additionally, populations do not usually exist in isolation. They engage in interspecific competition: that is, they share the environment with other species competing for the same resources. These factors are also important to understanding how a specific population will grow. Nature regulates population growth in a variety of ways. These are grouped into density-dependent factors, in which the density of the population at a given time affects growth rate and mortality, and density-independent factors, which influence mortality in a population regardless of population density. Note that in the former, the effect of the factor on the population depends on the density of the population at onset. Conservation biologists want to understand both types because this helps them manage populations and prevent extinction or overpopulation. Density-Dependent Regulation Most density-dependent factors are biological in nature (biotic), and include predation, inter- and intraspecific competition, accumulation of waste, and diseases such as those caused by parasites. Usually, the denser a population is, the greater its mortality rate. For example, during intra- and interspecific competition, the reproductive rates of the individuals will usually be lower, reducing their population’s rate of growth. In addition, low prey density increases the mortality of its predator because it has more difficulty locating its food source. An example of density-dependent regulation is shown in Figure 45.11 with results from a study focusing on the giant intestinal roundworm (Ascaris lumbricoides), a parasite of humans and other mammals. [3] Denser populations of the parasite exhibited lower fecundity: they contained fewer eggs. One possible explanation for this is that females would be smaller in more dense populations (due to limited resources) and that smaller females would have fewer eggs.

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  Basics of Plant Sciences

  • Khushboo Chaudhary, Pankaj Kumar Saraswat, Aniruddh Kumar Pareek(Authors)
  • 2023(Publication Date)
  • Delve Publishing

    (Publisher)

  Population Stabilization: Human birth rates have stabilized in most industrialized countries. Health: The incidence of life-threatening diseases has been reduced in most countries. Habitat Conservation: Deforestation has slowed & habitat protection has improved in some areas. Renewable Energy: Progress is being made in the transition to renewable energy sources. Freedom: Democracy is spreading around the world allowing local people to govern themselves. International Cooperation: helps solve global environmental problems An environmental management system brings together the people, policies, plans, review mechanisms, and procedures used to manage environmental issues at a facility or in an organization. Biotic factors are all of the living or once living things in an environment. Abiotic factors are all of the nonliving things in an environment. The interactions among living organisms such as plants and animals are called biotic factors, which may cause marked effects upon vegetation. The effects may be direct and indirect and modify the environment. The plants mostly live together in a community and influence one another. Similarly, animals in association with plants also affect plant life in one or several ways. The different interactions among them can be classified into the following two types they are positive interaction and negative interaction. Positive Interactions When one or both the participating species are benefited, it is positive interaction examples Mutualism and Commensalism. a. Mutualism: It is an interaction between two species of organisms in which both are benefitted from the obligate association. The following are common examples of mutualism. Environment- Environmental Management ond Control of Pollution... 127 Nitrogen fixation Rhizobium (Bacterium) forms nodules in the roots of leguminous plants and lives symbiotically.

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  Understanding Nature

  Ecology for a New Generation

  • Louise M. Weber(Author)
  • 2023(Publication Date)
  • CRC Press

    (Publisher)

  Anderson et al. 1955 ).

  Lakes have herbivores like the crustacean Daphnia that eat the phytoplankton. Use the idea of diminishing returns as part of your hypothesis for explaining how phytoplankton can recover from frequent steep declines in abundance.

  In the Equilibrium Debate, Who Was Right?

  Population growth curves from real species do not confirm the contention of equilibrists that populations stabilize around an equilibrium. At best, populations are weakly regulated (Ziebarth and Abbott 2010 ). Most non-microbe species have abundances with a range of variability, and growth tends to be boom and busty. The more interesting question is, what causes the variability? Beyond abiotic factors like weather, biotic factors like the Allee effect, stunting, and self-thinning account for some of the deviations from the logistic.

  There were other factors to discover beginning in the 1960s. One technique called key factor analysis was used to determine the greatest cause of death within each age group of a population (Begon et al. 1996 ). Using life tables, individuals in the population had to be laboriously tracked until death. For example, in a population of Colorado Potato Beetle (Begon et al. 1996 , Harcourt 1971 ), the percentage of eggs that washed into a puddle during a hard rain was compared to the percentage of larvae preyed upon. These were compared to the percentage of adults that dispersed during migration and compared to the percentage that died during hibernation in an early frost.

  The conclusion from many studies was that a complex combination of biotic and abiotic factors contributes to mortality overall in populations. Neither biotic nor abiotic factors are universally more prevalent. The highest source of mortality might change from year to year even for a single species or population (Begon et al. 1996

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  The Environment

  Science, Issues, and Solutions

  • Mohan K. Wali, Fatih Evrendilek, M. Siobhan Fennessy(Authors)
  • 2009(Publication Date)
  • CRC Press

    (Publisher)

  This, in turn, may lead to decreased survival and reproduction within the population. As a con-sequence, population growth will slow or may even become negative. Such populations could be regarded as self-regulating systems. Historically, nearly all of the population ecology concepts have come from the studies conducted by animal ecologists. It was rela-tively recently that these concepts have been applied to terrestrial plant ecology, which will be discussed in Chapter 9. Population Growth All organisms, without exception, have a pro-pensity to produce as many offspring as they can; if they do so, this leads to the intrinsic rate of population growth, also known as the “biotic potential” of the species. Thus, if envi-ronmental resources and other ecological con-ditions do not constrain population growth, exponential growth will occur. For example, if a single cell of baker’s yeast ( Saccharomyces cervisiae ) were to reproduce unconstrained, it is estimated that in just 2 weeks it could form a layer around the Earth that would be 3 m deep (Hofman 1992). A pair of fruit flies may in one year produce a mind-boggling 10 41 descendants (Evans 1995). Similarly, if the biotic potential of a mating pair of houseflies were actually reached, the number of flies in the seventh generation would be 5.7 trillion (Table 8.1) (Kormondy 1996). These stupendous numbers illustrate the power of exponential growth (See Box 8.1). If a population were to achieve exponential growth with unlimited availability of resources such Table 8.1 Biotic Potential of House Flies ( Musca domestica ) in 1 Year a Generation Total Population If All Survive 1 Year But Reproduce Only Once 1 120 2 7,320 3 439,520 4 26,359,320 5 1,581,559,320 6 94,893559,320 7 5,693,623,559,320 Source: From Kormondy, E. J. 1996. Concepts of Ecology, 4th ed. Upper Saddle River, NJ: Prentice Hall.

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  Ecotoxicology

  A Comprehensive Treatment

  • Michael C. Newman, William H. Clements(Authors)
  • 2007(Publication Date)
  • CRC Press

    (Publisher)

  Each factor is represented as a filter that operates at different spatial and temporal scales to determine regional, local, and microhabitat species pools. The pore size of each filter reflects its relative influence on species pools. Using this model, contaminants and other anthropogenic stressors are simply additional filters that determine community composition. (Modified from Figure 1 in Poff (1997).) Biotic and Abiotic Factors That Regulate Communities 381 21.1.1 C OLONIZATION AND C OMMUNITY S TRUCTURE Ecologists recognize that historical factors and regional-scale processes often interact to regulate local community composition. Colonization studies of newly created habitats provide opportunities to assess the influence of historical factors and species’ dispersal abilities on community compos-ition. If communities were regulated entirely by local deterministic factors, we would expect that communities established in similar habitats would have similar composition. Jenkins and Buikema (1998) tested this hypothesis by measuring structural and functional characteristics of zooplank-ton communities in 12 newly established ponds. Samples collected over a 1-year period showed that physical and chemical characteristics of these ponds were essentially identical. However, com-munities established in each of the ponds were distinct, reflecting the unique colonization abilities of dominant zooplankton species. Dispersal ability regulated composition among ponds because species that arrived first had a lasting effect on community structure. These results have important implications for how we view the establishment and regulation of communities. Failure to account for regional processes may explain the apparent stochastic behavior observed in some communities.

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