Ultimately, limiting factors determine a habitat's carrying capacity, which is the maximum size of the population it can support. Teach your students about limiting factors with this curated collection of resources.
Population density is the concentration of individuals within a species in a specific geographic locale. Population density data can be used to quantify demographic information and to assess relationships with ecosystems, human health, and infrastructure.
What are the most densely populated places in the world? Find out with MapMaker, National Geographic's classroom interactive mapping tool. Density is the number of things—which could be people, animals, plants, or objects—in a certain area.
Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Image Rabbits in the Field Female cottontail rabbits Sylvilagus floridanus are especially fertile, able to give birth to seven litters a year.
Twitter Facebook Pinterest Google Classroom. Encyclopedic Entry Vocabulary. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.
Media If a media asset is downloadable, a download button appears in the corner of the media viewer. Text Text on this page is printable and can be used according to our Terms of Service. Interactives Any interactives on this page can only be played while you are visiting our website. Related Resources. Limiting Factors. A single-limiting factor is when there is one factor that limits the system. A co-limiting factor is when a factor affects the population of organisms in an ecosystem indirectly but increases the limitation of the factor directly affecting the population.
In the law of the size of a population, a population will grow exponentially as long as the environment from where all individuals in that population are exposed to remains constant. However, there will come a time when the population will reach the maximum at which the environment can sustain. This is called the carrying capacity , the maximum load of the environment. Carrying capacity is the number of individuals that an environment can sustain without ending in damage or destruction to the organisms and the environment.
Thus, population size may increase until carrying capacity is met. Above this capacity, the population size will eventually decrease. The determiners of carrying capacity are limiting factors. The common limiting factors in an ecosystem are food, water, habitat, and mate. The availability of these factors will affect the carrying capacity of an environment. As population increases, food demand increases as well.
Since food is a limited resource, organisms will begin competing for it. The same thing goes for space, nutrients, and mate. Since these resources are available for a limited amount over a given period of time, inhabitants of a particular ecosystem will compete, possibly against the same species intraspecific competition or against other group of species interspecific competition. The deer populations, for instance, could decline if predation is high. If the number of wolves is relatively greater than the number of deer as their prey, the number of deer could drop.
However, with the dwindling number of deer, the number of wolves could also eventually decline. This predator-prey factor is an example of a biotic factor in an ecosystem. While a biotic factor includes the activities of a living component of an ecosystem, an abiotic factor includes the various physico-chemical factors in an ecosystem.
The common loon nests on land near large lakes. Some loon nesting places have been taken over by human development and the loon population has decreased.
Pollution can also hurt animal and plant populations. Sometimes hunting can impact animal populations. Whale populations have been lowered because of overhunting. If the balance between predator and prey is changed, populations are changed. In the freshwater Laurentian Great Lakes, particularly in Lake Erie, the factor limiting algal growth was found to be phosphorus. David Schindler and his colleagues at the Experimental Lakes Area Ontario, Canada demonstrated that phosphorus was the growth-limiting factor in temperate North American lakes using whole-lake treatment and controls Schindler This work encouraged the passage of the Great Lakes Water Quality Agreement of GLWQA — a reduction in phosphorus load from municipal sources was predicted to lead to a corresponding reduction in the total algal biomass and harmful cyanobacterial blue-green algae blooms McGuken ; Figure 3.
As annual phosphorus loads decreased in the mid s Dolan , there was some indication that Lake Erie was improving in terms of decreased total phytoplankton photosynthetic algae and cyanobacteria biomass Makarewicz Further improvement continued until the mid s, until an introduced species, the zebra mussel, began altering the internal phosphorus dynamics of the lake by mineralization excretion of digested algae Figure 3; Conroy et al.
C Change in Lake Erie seasonal average phytoplankton biomass in the central. Pollutants also contribute to environmental stress, limiting the growth rates of populations. Although each species has specific tolerances for environmental toxins, amphibians in general are particularly susceptible to pollutants in the environment. For example, pesticides and other endocrine disrupting toxins can strongly control the growth of amphibians Blaustein et al.
These chemicals are used to control agricultural pests but also run into freshwater streams and ponds where amphibians live and breed. They affect the amphibians both with direct increases in mortality and indirect limitation in growth, development, and reduction in fecundity.
Rohr et al. These effects limit population growth irrespective of the size of the amphibian population and are not limited to pesticides but also include pH and thermal pollution, herbicides, fungicides, heavy metal contaminations, etc.
Environmental catastrophes such as fires, earthquakes, volcanoes and floods can strongly affect population growth rates via direct mortality and habitat destruction. A large-scale natural catastrophe occurred in when hurricane Katrina impacted the coastal regions of the Gulf of Mexico in the southern United States.
Katrina altered habitat for coastal vegetation by depositing more than 5 cm of sediment over the entire coastal wetland zone. In these areas, substantial improvement in the quality of wetlands for plant growth occurred after many years of wetland loss due to control of the Mississippi River flow Turner et al. At the same time, however, almost km 2 of wetland was destroyed and converted to open sea, completely eliminating wetland vegetation Day et al.
More recently the Gulf oil spill in has again impacted the coastal wetland vegetation. Though human derived, this large-scale environmental disaster will have long-term impacts on the population growth of not only vegetation but all organisms in the wetlands and nearshore regions of the Gulf of Mexico. Blaustein, A. Ultraviolet radiation, toxic chemicals and amphibian population declines. Diversity and Distributions 9, — Clutton-Brock, T. Sex differences in emigration and mortality affect optimal management of deer populations.
Nature , — Conroy, J. Recent increases in Lake Erie plankton biomass: roles of external phosphorus loading and dreissenid mussels. Journal of Great Lakes Research 31 Supplement 2 , 89— Day, J. Restoration of the Mississippi delta: lessons from hurricanes Katrina and Rita. Science , — Gilg, O. Cyclic dynamics in a simple vertebrate predator-prey community. Makarewicz, J. Phytoplankton biomass and species composition in Lake Erie, to Journal of Great Lakes Research 19, — McGucken, W.
Rohr, J. Lethal and sublethal effects of atrazine, carbaryl, endosulfan, and octylphenol on the streamside salamander Ambystoma barbouri. Environmental Toxicology and Chemistry 22, — Schindler, D.
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