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105 rows, page 19 of 27 (4/p)
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Export to Excel select * from OriginOfSpecies where subject = '04 - Natural Selection' order by subject, title, ordinal limit 72, 4 (Page 19: Row)
04 - Natural Selection 04-11 - Divergence of Character 170 But during the process of modification, represented in the diagram, another of our principles, namely that of extinction, will have played an important part.
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As in each fully stocked country natural selection necessarily acts by the selected form having some advantage in the struggle for life over other forms, there will be a constant tendency in the improved descendants of any one species to supplant and exterminate in each stage of descent their predecessors and their original progenitor.

For it should be remembered that the competition will generally be most severe between those forms which are most nearly related to each other in habits, constitution, and structure.

Hence all the intermediate forms between the earlier and later states, that is between the less and more improved states of the same species, as well as the original parent-species itself, will generally tend to become extinct. So it probably will be with many whole collateral lines of descent, which will be conquered by later and improved lines.

If, however, the modified offspring of a species get into some distinct country, or become quickly adapted to some quite new station, in which offspring and progenitor do not come into competition, both may continue to exist.
04 - Natural Selection 04-11 - Divergence of Character 180 If, then, our diagram be assumed to represent a considerable amount of modification, species (A) and all the earlier varieties will have become extinct, being replaced by eight new species (a14 to m14); and species (I) will be replaced by six (n14 to z14) new species.
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04 - Natural Selection 04-11 - Divergence of Character 190 But we may go further than this.

The original species of our genus were supposed to resemble each other in unequal degrees, as is so generally the case in nature; species (A) being more nearly related to B, C, and D, than to the other species; and species (I) more to G, H, K, L, than to the others.
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These two species (A) and (I) were also supposed to be very common and widely diffused species, so that they must originally have had some advantage over most of the other species of the genus.

Their modified descendants, fourteen in number at the fourteen-thousandth generation will probably have inherited some of the same advantages: they have also been modified and improved in a diversified manner at each stage of descent, so as to have become adapted to many related places in the natural economy of their country. It seems, therefore, extremely probable that they will have taken the places of, and thus exterminated not only their parents (A) and (I), but likewise some of the original species which were most nearly related to their parents. Hence very few of the original species will have transmitted offspring to the fourteen-thousandth generation.

We may suppose that only one, (F), of the two species (E and F) which were least closely related to the other nine original species, has transmitted descendants to this late stage of descent.
04 - Natural Selection 04-11 - Divergence of Character 200 The new species in our diagram descended from the original eleven species, will now be fifteen in number.

Owing to the divergent tendency of natural selection, the extreme amount of difference in character between species a14 and z14 will be much greater than that between the most distinct of the original eleven species.
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The new species, moreover, will be allied to each other in a widely different manner. Of the eight descendants from (A) the three marked a14, q14, p14, will be nearly related from having recently branched off from a10; b14, and f14, from having diverged at an earlier period from a1, will be in some degree distinct from the three first-named species; and lastly, o14, e14, and m14, will be nearly related one to the other, but, from having diverged at the first commencement of the process of modification, will be widely different from the other five species, and may constitute a sub-genus or a distinct genus.