Which density dependent factors other than

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. 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:. 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. 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.

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Limiting Factors. View Collection. Population Density. View Article. MapMaker: Population Density. View Map. Educational Resources in Your Inbox. Educational Resources in Your Inbox Join our community of educators and receive the latest information on National Geographic's resources for you and your students. While the previously mentioned density-dependant factors are often biotic, density-independent factors are often abiotic. These density-independent factors include food or nutrient limitation, pollutants in the environment, and climate extremes, including seasonal cycles such as monsoons.

In addition, catastrophic factors can also impact population growth, such as fires and hurricanes. The quality of nutrients e. The lower the quality of the nutrients, the higher the environmental stress. 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. Eutrophication and recovery in experimental lakes: implications for lake management.

Sibley, R. Population growth rate and its determinants: an overview. Philosophical Transactions of the Royal Society B , — Turner, R. Wetland Sedimentation from Hurricanes Katrina and Rita. Wauters, L. Effects of food availability and density on red squirrel Sciurus vulgaris reproduction. Ecology 76, —