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Many of the constants have been derived from reaction of so-called benzhydrylium ions as the electrophiles: [10] and a diverse collection of π-nucleophiles: . Typical E values are +6.2 for R = chlorine, +5.90 for R = hydrogen, 0 for R = methoxy and −7.02 for R = dimethylamine.
In 2011 a study published in PLoS Biology estimated there to be 8.7 million ± 1.3 million eukaryotic species on Earth. [11] By 2017, most estimates projected there to be around 11 million species or fewer on Earth. [4] A 2017 study estimated there are around at least 1 to 6 billion species, 70-90% of which are bacteria. [4]
The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms.This number, along with the visual appearance of the chromosome, is known as the karyotype, [1] [2] [3] and can be found by looking at the chromosomes through a microscope.
Recent figures indicate that there are more than 1.4 billion insects for each human on the planet, [27] or roughly 10 19 (10 quintillion) individual living insects on the earth at any given time. [28] An article in The New York Times claimed that the world holds 300 pounds of insects for every pound of humans. [28]
Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million in total. Animals range in size from 8.5 millionths of a metre to 33.6 metres (110 ft) long and have complex interactions with each other and their environments, forming intricate food webs .
Their existence could be seen as an indication that there is nothing special about the four natural nucleobases that evolved on Earth. [70] [71] On the other hand, DNA is tightly related to RNA which does not only act as a transcript of DNA but also performs as molecular machines many tasks in cells. For this purpose it has to fold into a ...
It is estimated that more than 99% of all species that ever existed on Earth, amounting to over five billion species, [3] are extinct. [4] [5] Earth is the only celestial body known to harbor life forms. No form of extraterrestrial life has yet been discovered. [6]
In 1962, Edwards and Pearson (the latter of HSAB theory) introduced the phrase alpha effect for this anomaly. He offered the suggestion that the effect was caused by a transition state (TS) stabilization effect: on entering the TS the free electron pair on the nucleophile moves away from the nucleus, causing a partial positive charge which can be stabilized by an adjacent lone pair as for ...