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OriginOfSpecies - 475 Rows
Column Type #Values Column Stats
id int(11) 475 Column Stats
subject varchar(80) 14 Column Stats
title varchar(250) 139 Column Stats
ordinal int(11) 30 Column Stats
description text 474 Column Stats

475 rows, page 11 of 119 (4/p)
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Export to Excel select * from OriginOfSpecies order by ordinal limit 40, 4 (Page 11: Row)
subject
title
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04 - Natural Selection 04-10 - Extinction caused by Natural Selection 10 This subject will he more fully discussed in our chapter on Geology; but it must here be alluded to from being intimately connected with natural selection.

Natural selection acts solely through the preservation of variations in some way advantageous, which consequently endure.

Owing to the high geometrical rate of increase of all organic beings, each area is already fully stocked with inhabitants; and it follows from this, that as the favoured forms increase in number, so, generally, will the less favoured decrease and become rare.

Rarity, as geology tells us, is the precursor to extinction.

We can see that any form which is represented by few individuals will run a good chance of utter extinction, during great fluctuations in the nature of the seasons, or from a temporary increase in the number of its enemies.

But we may go further than this; for, as new forms are produced, unless we admit that specific forms can go on indefinitely increasing in number, many old forms must become extinct.

That the number of specific forms has not indefinitely increased, geology plainly tells us; and we shall presently attempt to show why it is that the number of species throughout the world has not become immeasurably great.

Dodo
Dodo
04 - Natural Selection 04-11 - Divergence of Character 10 The principle, which I have designated by this term, is of high importance, and explains, as I believe, several important facts.

In the first place, varieties, even strongly-marked ones, though having somewhat of the character of species- as is shown by the hopeless doubts in many cases how to rank them- yet certainly differ far less from each other than do good and distinct species.

Nevertheless, according to my view, varieties are species in the process of formation, or are, as I have called them, incipient species.

How, then, does the lesser difference between varieties become augmented into the greater difference between species?

That this does habitually happen, we must infer from most of the innumerable species throughout nature presenting well-marked differences; whereas varieties, the supposed prototypes and parents of future well-marked species, present slight and ill-defined differences.

Mere chance, as we may call it, might cause one variety to differ in some character from its parents, and the offspring of this variety again to differ from its parent in the very same character and in a greater degree; but this alone would never account for so habitual and large a degree of difference as that between the species of the same genus.
04 - Natural Selection 04-12 - On the Degree to which Organisation tends to advance 10 Natural Selection acts exclusively by the preservation and accumulation of variations, which are beneficial under the organic and inorganic conditions to which each creature is exposed at all periods of life.

The ultimate result is that each creature tends to become more and more improved in relation to its conditions.

This improvement inevitable leads to the gradual advancement of the organisation of the greater number of living beings throughout the world.

But here we enter on a very intricate subject, for naturalists have not defined to each other's satisfaction what is meant by an advance in organisation.
04 - Natural Selection 04-13 - Convergence of Character 10 Mr. H. C. Watson thinks that I have overrated the importance of divergence of character (in which, however, he apparently believes) and that convergence, as it may be called, has likewise played a part. If two species, belonging to two distinct though allied genera, had both produced a large number of new and divergent forms, it is conceivable that these might approach each other so closely that they would have all to be classed under the same genus; and thus the descendants of two distinct genera would converge into one.