residence time

Examples of residence time in the following topics:

• The Water (Hydrologic) Cycle

  • Although this pursuit of drinkable water has been ongoing throughout human history, the supply of fresh water is still a major issue in modern times.
  • Residence time is a measure of the average time an individual water molecule stays in a particular reservoir.
  • Over time, this water vapor condenses into clouds as liquid or frozen droplets, which is eventually followed by precipitation (rain or snow), returning water to the earth's surface.
  • This graph shows the average residence time for water molecules in the earth's water reservoirs.

• The Phosphorus Cycle

  • This sediment then is moved to land over geologic time by the uplifting of areas of the earth's surface .
  • The movement of phosphate from the ocean to the land and through the soil is extremely slow, with the average phosphate ion having an oceanic residence time between 20,000 and 100,000 years.

• Endosymbiosis and the Evolution of Eukaryotes

  • Eukaryotes may have been a product of one cell engulfing another and evolving over time until the separate cells became a single organism.
  • To fully understand eukaryotic organisms, it is necessary to understand that all extant eukaryotes are descendants of a chimeric organism that was a composite of a host cell and the cell(s) of an alpha-proteobacterium that "took up residence" inside the host.

• Reproductive Isolation

  • Given enough time, the genetic and phenotypic divergence between populations will affect characters that influence reproduction: if individuals of the two populations were to be brought together, mating would be improbable, but if mating did occur, offspring would be non-viable or infertile.
  • Many organisms only reproduce at certain times of the year, often just annually.
  • In some cases, populations of a species move to a new habitat and take up residence in a place that no longer overlaps with other populations of the same species; this is called habitat isolation.
  • Over time, the forces of natural selection, mutation, and genetic drift will likely result in the divergence of the two groups .

• Allopatric Speciation

  • When that separation continues for a period of time, the two populations are able to evolve along different trajectories.
  • If two flying insect populations took up residence in separate nearby valleys, chances are individuals from each population would fly back and forth, continuing gene flow.
  • Over time, the varied demands of their new lifestyles lead to multiple speciation events originating from a single species.

• Energy Sources

  • In aquatic ecosystems, the availability of light may be limited because sunlight is absorbed by water, plants, suspended particles, and resident microorganisms.
  • When this occurs, the energy found in that organism is sequestered for some time unless ocean upwelling occurs.

• Antibiotics: Are We Facing a Crisis?

  • Researchers have expressed concern about the way this latter source of MRSA targets a much younger population than those residing in care facilities.
  • Some scientists believe that after years of being protected from bacterial infections by antibiotics, we may be returning to a time in which a simple bacterial infection could again devastate the human population.

• Protists as Primary Producers, Food Sources, and Symbionts

  • This explains why reef-building corals do not reside in waters deeper than 20 meters: insufficient light reaches those depths for dinoflagellates to photosynthesize.

• Hormone Functions

  • Cellular recipients of a particular hormonal signal may be one of several cell types that reside within a number of different tissues, as is the case for insulin, which triggers a diverse range of systemic physiological effects.

• Excitation–Contraction Coupling

  • AChE resides in the synaptic cleft, breaking down ACh so that it does not remain bound to ACh receptors, which would cause unwanted extended muscle contraction.