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As metabolic rate increases, the lifespan of an organism is expected to decrease as a direct result. The rate at which this occurs is not fixed and thus the -45° slope in this graph is just an example and not a constant. The rate of living theory postulates that the faster an organism's metabolism, the shorter its lifespan.
The key to life history theory is that there are limited resources available, and focusing on only a few life history characteristics is necessary. Examples of some major life history characteristics include: Age at first reproductive event; Reproductive lifespan and ageing; Number and size of offspring
This example of a survival tree analysis uses the R package "rpart". [8] The example is based on 146 stage C prostate cancer patients in the data set stagec in rpart. Rpart and the stagec example are described in Atkinson and Therneau (1997), [9] which is also distributed as a vignette of the rpart package. [8] The variables in stages are:
Starting in 1985, researchers proposed that life arose at hydrothermal vents, [237] [238] that spontaneous chemistry in the Earth's crust driven by rock–water interactions at disequilibrium thermodynamically underpinned life's origin [239] [240] and that the founding lineages of the archaea and bacteria were H 2-dependent autotrophs that used ...
"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 ...
At this point, panspermia as a theory now had a potentially viable transport mechanism, as well as a vehicle for carrying life from planet to planet. The theory still faced criticism mostly due to doubts about how long spores would actually survive under the conditions of their transport from one planet, through space, to another. [25]
The theory was popular in the 1970s and 1980s, when it was used as a heuristic device, but lost importance in the early 1990s, when it was criticized by several empirical studies. [5] [6] A life-history paradigm has replaced the r/K selection paradigm, but continues to incorporate its important themes as a subset of life history theory. [7]
A scenario is a set of related concepts pertinent to the origin of life (abiogenesis), such as the iron-sulfur world.Many alternative abiogenesis scenarios have been proposed by scientists in a variety of fields from the 1950s onwards in an attempt to explain how the complex mechanisms of life could have come into existence.