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Export to Excel select * from OriginOfSpecies where ordinal = '10' order by description limit 116, 4 (Page 30: Row)
subject
title
ordinal
description Desending Order (top row is first)
04 - Natural Selection 04-09 - Circumstances favourable for the production of new forms through Natural Selection 10 This is an extremely intricate subject.

A great amount of variability, under which term individual differences are always included, will evidently be favourable.

A large number of individuals, by giving a better chance within any given period for the appearance of profitable variations, will compensate for a lesser amount of variability in each individual, and is, I believe, a highly important element of success.

Though Nature grants long periods of time for the work of natural selection, she does not grant an indefinite period; for as all organic beings are striving to seize on each place in the economy of nature, if any one species does not become modified and improved in a corresponding degree with its competitors, it will be exterminated.

Cheetah
Cheetah
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
01 - Variations Under Domestication 01-13 - Summary 10 To sum up on the origin of our domestic races of animals and plants.

Changed conditions of life are of the highest importance in causing variability, both by acting directly on the organisation, and indirectly by affecting the reproductive system.

It is not probable that variability is an inherent and necessary contingent, under all circumstances.

The greater or less force of inheritance and reversion, determine whether variations shall endure.

Variability is governed by many unknown laws, of which correlated growth is probably the most important.

Something, but how much we do not know, may be attributed to the definite action of the conditions of life. Some, perhaps a great, effect may be attributed to the increased use or disuse of parts.

The final result is thus rendered infinitely complex.

In some cases the intercrossing of aboriginally distinct species appears to have played an important part in the origin of our breeds.

When several breeds have once been formed in any country, their occasional intercrossing, with the aid of selection, has, no doubt, largely aided in the formation of new sub-breeds; but the importance of crossing has been much exaggerated, both in regard to animals and to those plants which are propagated by seed.
06 - Difficutiles in Theory 06-07 - Organs of extreme Perfection 10 To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree.

Eye
Eye


When it was first said that the sun stood still and the world turned round, the common sense of mankind declared the doctrine false; but the old saying of Vox populi, vox Dei, as every philosopher knows, cannot be trusted in science.

Nicolaus Copernicus
Nicolaus Copernicus


Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor, as is certainly the case; if further, the eye ever varies and the variations be inherited, as is likewise certainly the case and if such variations should be useful to any animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, should not be considered as subversive of the theory.

How a nerve comes to be sensitive to light, hardly concerns us more than how life itself originated; but I may remark that, as some of the lowest organisms, in which nerves cannot be detected, are capable of perceiving light, it does not seem impossible that certain sensitive elements in their sarcode should become aggregated and developed into nerves, endowed with this special sensibility.

lightning
lightning