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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 74 of 119 (4/p)
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Export to Excel select * from OriginOfSpecies order by ordinal limit 292, 4 (Page 74: Row)
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description
04 - Natural Selection 04-09 - Circumstances favourable for the production of new forms through Natural Selection 40 Even with animals which unite for each birth, and which do not propagate rapidly, we must not assume that free intercrossing would always eliminate the effects of natural selection; for I can bring forward a considerable body of facts showing that within the same area, two varieties of the same animal may long remain distinct, from haunting different stations, from breeding at slightly different seasons, or from the individuals of each variety preferring to pair together.
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04 - Natural Selection 04-11 - Divergence of Character 40 We can clearly discern this in the case of animals with simple habits.

Take the case of a carnivorous quadruped, of which the number that can be supported in any country has long ago arrived at its full average.

If its natural power of increase be allowed to act, it can succeed in increasing (the country not undergoing any change in conditions) only by its varying descendants seizing on places at present occupied by other animals: some of them, for instance, being enabled to feed on new kinds of prey, either dead or alive; some inhabiting new stations, climbing trees, frequenting water, and some perhaps becoming less carnivorous.

quadruped
quadruped

carnivore
carnivore

herbivore
herbivore


The more diversified in habits and structure the descendants of our carnivorous animals become, the more places they will be enabled to occupy.

What applies to one animal will apply throughout all time to all animals- that is, if they vary- for otherwise natural selection can effect nothing.

So it will be with plants. It has been experimentally proved, that if a plot of ground be sown with one species of grass, and a similar plot be sown with several distinct genera of grasses, a greater number of plants and a greater weight of dry herbage can be raised in the latter than in the former case.

grass
grass


The same has been found to hold good when one variety and several mixed varieties of wheat have been sown on equal spaces of ground.

wheat
wheat


Hence, if any one species of grass were to go on varying, and the varieties were continually selected which differed from each other in the same manner, though in a very slight degree, as do the distinct species and genera of grasses, a greater number of individual plants of this species, including its modified descendants, would succeed in living on the same piece of ground.

And we know that each species and each variety of grass is annually sowing almost countless seeds; and is thus striving, as it may be said, to the utmost to increase in number.

Consequently, in the course of many thousand generations, the most distinct varieties of any one species of grass would have the best chance of succeeding and of increasing in numbers, and thus of supplanting the less distinct varieties; and varieties, when rendered very distinct from each other, take the rank of species.

grass
grass
04 - Natural Selection 04-12 - On the Degree to which Organisation tends to advance 40 If we take as the standard of high organisation, the amount of differentiation and specialisation of the several organs in each being when adult (and this will include the advancement of the brain for intellectual purposes), natural selection clearly leads towards this standard: for all physiologists admit that the specialisation of organs, inasmuch as in this state they perform their functions better, is an advantage to each being; and hence the accumulation of variations tending towards specialisation is within the scope of natural selection.

On the other hand, we can see, bearing in mind that all organic beings are striving to increase at a high ratio and to seize on every unoccupied or less well occupied place in the economy of nature, that it is quite possible for natural selection gradually to fit a being to a situation in which several organs would be superfluous or useless: in such cases there would be retrogression in the scale of
organisation.

appendix
appendix
06 - Difficutiles in Theory 06-09 - Cases of Difficulty 40 In the foregoing cases, we see the same end gained and the same function performed, in beings not at all or only remotely allied, by organs in appearance, though not in development, closely similar.

On the other hand, it is a common rule throughout nature that the same end should be gained, even sometimes in the case of closely-related beings, by the most diversified means.

How differently constructed is the feathered wing of a bird and the membrane-covered wing of a bat; and still more so the four wings of a butterfly, the two wings of a fly, and the two wings with the elytra of a beetle.
bird
bird

bat
bat

butterfly
butterfly

fly
fly

beetle
beetle

elytra
elytra


Bivalve shells are made to open and shut, but on what a number of patterns is the hinge constructed,- from the long row of neatly interlocking teeth in a Nucula to the simple ligament of a Mussel!
Sea Shell
Sea Shell

nucula
nucula

mussel
mussel


Seeds are disseminated by their minuteness,- by their capsule being converted into a light balloon-like envelope,- by being embedded in pulp or flesh, formed of the most diverse parts, and rendered nutritious, as well as conspicuously coloured, so as to attract and be devoured by birds,- by having hooks and grapnels of many kinds and serrated arms, so as to adhere to the fur of quadrupeds,- and by being furnished with wings and plumes, as different in shape as they are elegant in structure, so as to be wafted by every breeze.
Flying Seeds
Flying Seeds


I will give one other instance; for this subject of the same end being gained by the most diversified means well deserves attention.

Some authors maintain that organic beings have been formed in many ways for the sake of mere variety, almost like toys in a shop, but such a view of nature is incredible.

With plants having separated sexes, and with those in which, though hermaphrodites, the pollen does not spontaneously fall on the stigma, some aid is necessary for their fertilisation.

With several kinds this is effected by the pollen-grains, which are light and incoherent, being blown by the wind through mere chance on to the stigma; and this is the simplest plan which can well be conceived.
pollen
pollen


An almost equally simple, though very different, plan occurs in many plants in which a symmetrical flower secretes a few drops of nectar, and is consequently visited by insects; and these carry the pollen from the anthers to the stigma.
anther
anther