Comparison with 1872 |
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Text in this page (from paragraph 3200, sentence 400, word 57 to paragraph 3200, sentence 400, word 61) is not present in 1872 |
Lastly,
isolation isolation 1869 1872 | isolation, 1859 1860 1861 1866 |
...OMIT 1869 1872 |
by checking immigration and consequently competition, 1859 1860 1861 1866 |
will give time for
a a 1869 1872 | any 1859 1860 1861 1866 |
new variety to be
....... 1872 | slowly 1859 1860 1861 1866 1869 |
improved improved 1872 | improved; 1859 1860 1861 1866 1869 |
at a slow rate; and at a slow rate; and 1872 |
and 1859 1860 1861 1866 1869 |
this may sometimes be of
much importance. much importance. 1872 |
importance in the production of new species. 1859 1860 1861 1866 1869 |
If, however, an isolated area be very small, either from being surrounded by barriers, or from having very peculiar physical conditions, the total number of the
inhabitants will be inhabitants will be 1869 1872 |
individuals supported on it will necessarily be very 1859 1860 1861 1866 |
small; and
this will this will 1869 1872 |
fewness of individuals will greatly 1859 1860 1861 1866 |
retard the production of new species through natural selection, by decreasing the
chances chances 1869 1872 | chance 1859 1860 1861 1866 |
of
...OMIT 1872 |
the appearance of 1859 1860 1861 1866 1869 |
favourable
variations arising. variations arising. 1872 | variations. 1859 1860 1861 1866 | individual differences. 1869 |
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The mere lapse of time by itself does nothing
either for or against natural selection. I state this because it has been erroneously asserted that the element of time is
assumed by me to play an all-important part in natural selection,
as if all species
were necessarily undergoing
slow modification from
some innate law. Lapse of time is only so far highly
important, as
it gives a better chance of beneficial variations arising, being
selected, accumulated,
and fixed,
in relation to the slowly changing organic and inorganic conditions of life.
It likewise favours
the
direct
action of new or changed physical
conditions of life.
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If we turn to nature to test the truth of these remarks, and look at any small isolated area, such as an oceanic island, although the
....... 1869 1872 | total 1859 1860 1861 1866 |
number of
....... 1872 | the 1859 1860 1861 1866 1869 |
species inhabiting it is species inhabiting it is 1872 |
species inhabiting it, will be found to be 1859 1860 1861 |
species inhabiting it will be found to be 1866 |
different species inhabiting it is 1869 |
small, as we shall see in our chapter on
Geographical Geographical 1861 1866 1869 1872 | geographical 1859 1860 |
Distribution; Distribution; 1861 1866 1869 1872 | distribution; 1859 1860 |
yet of these
species a very large proportion are endemic,— that is, have been produced there, and nowhere
else in the world. else in the world. 1869 1872 |
else. 1859 1860 1861 1866 |
Hence an oceanic island at first sight seems to have been highly favourable for the production of new species. But we may thus
....... 1869 1872 | greatly 1859 1860 1861 1866 |
deceive ourselves, for to ascertain whether a small isolated area, or a large open area like a continent, has been most favourable for the production of new organic forms, we ought to make the comparison within equal times; and this we are incapable of doing. |
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Although
...OMIT 1861 1866 1869 1872 |
I do not doubt that 1859 1860 |
isolation is of
great great 1869 1872 | considerable 1859 1860 1861 1866 |
importance in the production of new species, on the whole I am inclined to believe that largeness of area is
still still 1869 1872 | of 1859 1860 1861 1866 |
more
important, important, 1869 1872 | importance, 1859 1860 1861 1866 |
....... 1861 1866 1869 1872 | more 1859 1860 |
especially
for for 1869 1872 | in 1859 1860 1861 1866 |
the production of
species species 1872 | species, 1859 1860 1861 1866 1869 |
which
shall shall 1869 1872 | will 1859 1860 1861 1866 |
prove capable of enduring for a long period, and of spreading widely. Throughout a great and open area, not only will there be a better chance of favourable
variations, variations, 1872 | variations 1859 1860 1861 1866 1869 |
arising from the large number of individuals of the same species
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