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Extinctions are a normal part of the evolutionary process, and the background extinction rate is a measurement of "how often" they naturally occur.Normal extinction rates are often used as a comparison to present day extinction rates, to illustrate the higher frequency of extinction today than in all periods of non-extinction events before it.
For example, in an article published in 2004, Otso Ovaskainen and Ilkka Hanski explained with an empirical example that when factors such as Allee effect or Rescue effect were included in modeling the extinction threshold, there were unexpected extinctions in a high number of species. A more complex model came up with different results, and in ...
More significantly, the current rate of global species extinctions is estimated as 100 to 1,000 times "background" rates (the average extinction rates in the evolutionary time scale of planet Earth), [71] [72] faster than at any other time in human history, [73] [74] while future rates are likely 10,000 times higher. [72]
"Now, here, you see, it takes all the running you can do, to keep in the same place." — Lewis Carroll [4]. In 1973, Leigh Van Valen proposed the hypothesis as an "explanatory tangent" to explain the "law of extinction" known as "Van Valen's law", [1] which states that the probability of extinction does not depend on the lifetime of the species or higher-rank taxon, instead being constant ...
Operant extinction differs from forgetting in that the latter refers to a decrease in the strength of a behavior over time when it has not been emitted. [6] For example, a child who climbs under his desk, a response which has been reinforced by attention, is subsequently ignored until the attention-seeking behavior no longer
The surviving populations are in continual decline in 43% of those that are threatened. Since the mid-1980s the actual rates of extinction have exceeded 211 times rates measured from the fossil record. [148] However, "The current amphibian extinction rate may range from 25,039 to 45,474 times the background extinction rate for amphibians."
[47] [48] For example, coral reefs—which are biodiversity hotspots—will be lost by the year 2100 if global warming continues at the current rate. [49] [50] Still, it is the general habitat destruction (often for expansion of agriculture), not climate change, that is currently the bigger driver of biodiversity loss.
The quasi-extinction threshold, or sometimes called the quasi-extinction risk is the population size below which a species is considered to be at extreme risk of quasi-extinction. [5] This threshold varies by species and is influenced by several factors, including reproductive rates, habitat requirements, and genetic diversity.