Constant parameters of homeostasis

These constants are not strictly fixed. There may be some deviation from the average in one way or another in a kind of "corridor". For each parameter limits the maximum possible deviations own. Also, they differ on the time during which the body can tolerate a violation of a specific parameter of homeostasis without any serious consequences.

Examples:

§ The homeostasis constants of animals are the volume, the composition of the blood and other body fluids.

§ Homeostasis is the maintenance of a population is determined by the spatial structure, density, and genetic diversity. Because of homeostatic regulation is maintained constant composition and populations in the community.

§ At the ecosystem level homeostasis is manifested in the most stable forms of interaction between the species, which is reflected in the adaptation to the peculiarities of the environment and the maintenance cycles cycling of nutrients.

Historically, ecological succession was seen as having a stable end-stage called the climax sometimes referred to as the 'potential biodiversity' of a site, shaped primarily by the local climate. This idea has been largely abandoned by modern ecologists in favor of non-equilibrium ideas of how ecosystems function, as most natural ecosystems experience disturbance at a rate that makes a "climax" community unattainable.

Only on small, isolated habitats known as ecological islands can the phenomenon be observed. One such case study is the island of Krakatoa after its major eruption in 1883: the established stable homeostasis of the previous forest climax ecosystem was destroyed, and all life was eliminated from the island. In the years after the eruption, Krakatoa went through a sequence of ecological changes in which successive groups of new plant or animal species followed one another, leading to increasing biodiversity and eventually culminating in a re-established climax community. This ecological succession on Krakatoa occurred in a number of stages; a sere is defined as "a stage in a sequence of events by which succession occurs". The complete chain of seres leading to a climax is called a prisere. In the case of Krakatoa, the island reached its climax community, with eight hundred different recorded species, in 1983, one hundred years after the eruption that cleared all life off the island. Evidence confirms that this number has been homeostatic for some time, with the introduction of new species rapidly leading to elimination of old ones. The evidence of Krakatoa, and other disturbed island ecosystems, has confirmed many principles of Island Biogeography, mimicking general principles of ecological succession albeit in a virtually closed system comprised almost exclusively of endemic species.

Picture 3. The Krakatoa

In the Gaia hypothesis, James Lovelock stated that the entire mass of living matter on Earth (or any planet with life) functions as a vast homeostatic superorganism that actively modifies its planetary environment to produce the environmental conditions necessary for its own survival. In this view, the entire planet maintains homeostasis. Whether this sort of system is present on Earth is still open to debate. However, some relatively simple homeostatic mechanisms are generally accepted. For example, it is sometimes claimed that when atmospheric carbon dioxide levels rise, certain plants are able to grow better and thus act to remove more carbon dioxide from the atmosphere. However, warming has exacerbated droughts, making water the actual limiting factor on land. When sunlight is plentiful and atmospheric temperature climbs, it has been claimed that the phytoplankton of the ocean surface waters may thrive and produce more dimethyl sulfide, DMS. The DMS molecules act ascloud condensation nuclei, which produce more clouds, and thus increase the atmospheric albedo, and this feeds back to lower the temperature of the atmosphere. However, rising sea temperature has stratified the oceans, separating warm, sunlit waters from cool, nutrient-rich waters. Thus, nutrients have become the limiting factor, and plankton levels have actually fallen over the past 50 years, not risen. As scientists discover more about Earth, vast numbers of positive and negative feedback loops are being discovered, that, together, maintain a metastable condition, sometimes within very broad range of environmental conditions. Environmental pressure, such as competition or change in temperature, can lead to adaptation/extinction of species over time.

Conclusions

Homeostasis is the property of a system that regulates its internal environment and tends to maintain a stable. It can be either an open or closed system. In simple terms, it is a process in which the body's internal environment is kept stable.

Date: 2015-12-11; view: 1019