Charles Darwin, NaturalistWilliam Brown, 1886 - Всего страниц: 32 |
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Стр. 6
... considered the subject of the struggle for existence : - " The supply of food on an average remains constant ; yet the tendency in every animal to increase by propagation is geometrical , and A its surprising effects have nowhere been ...
... considered the subject of the struggle for existence : - " The supply of food on an average remains constant ; yet the tendency in every animal to increase by propagation is geometrical , and A its surprising effects have nowhere been ...
Стр. 11
... considered the causes of variability , which , as we shall have occasion to suggest later , are as much in want of investigation now as when the Origin of Species " was published . Cultivated organisms are more variable than those in ...
... considered the causes of variability , which , as we shall have occasion to suggest later , are as much in want of investigation now as when the Origin of Species " was published . Cultivated organisms are more variable than those in ...
Стр. 15
... considered . The chief of these are the absence of transitions , the existence of instincts and organs of extreme com- plexity , and the fact that species when crossed are either sterile or produce sterile offspring , whereas varieties ...
... considered . The chief of these are the absence of transitions , the existence of instincts and organs of extreme com- plexity , and the fact that species when crossed are either sterile or produce sterile offspring , whereas varieties ...
Стр. 16
... considered the " Origin of Species " as only a general sketch of this theory and the facts which support it . He originally intended to treat each one of its chapters in greater detail , and so expand it into a volume . This plan was ...
... considered the " Origin of Species " as only a general sketch of this theory and the facts which support it . He originally intended to treat each one of its chapters in greater detail , and so expand it into a volume . This plan was ...
Стр. 29
... considered , the sur- vival of those individuals which are best adapted to the conditions of life , some of those conditions being human needs and desires . We can see But before we can attain a complete conception of universal ...
... considered , the sur- vival of those individuals which are best adapted to the conditions of life , some of those conditions being human needs and desires . We can see But before we can attain a complete conception of universal ...
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action of natural America Animals and Plants anthropomorphic arguments Aspalax belief biologists Buffon caudicle cause of modification causes of variation characters CHARLES DARWIN chlorophyll conception cross-fertilization is effected Darwin points descendants descent with modification divergence earth environment Erasmus Darwin evolved external conditions favourable flower fossil Galapagos Islands geographical distribution given species gradual greater number habits Herbert Spencer human selection hypothesis idea increase inhabitants inherited instance intermediate links larger number lated the variations leave more progeny lowly organized forms Madeira beetles modifica morphological rela natural selection naturalist number of cats number of individuals offspring organic evolution Origin of Species parents perfectly adapted phenomena Plants under Domestication pollinium present probable process of selection produced protoplasm Red clover reproductive cells structure struggle for existence studies domesticated animals survival tend theory of evolution theory of natural thought tion truth of organic Tucutuco universal evolution variability wants or pleasures whole species woodpecker
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Стр. 29 - There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.
Стр. 13 - There is no exception to the rule that every organic being naturally increases at so high a rate, that, if not destroyed, the earth would soon be covered by the progeny of a single pair.
Стр. 10 - ... species had not been independently created, but had descended, like varieties, from other species. Nevertheless, such a conclusion, even if well founded, would be unsatisfactory, until it could be shown how the innumerable species inhabiting this world have been modified, so as to acquire that perfection of structure and coadaptation which justly excites our admiration.
Стр. 24 - In one sense the conditions of life may be said, not only to cause variability, either directly or indirectly, but likewise to include natural selection ; for the conditions determine whether this or that variety shall survive. But when man is the selecting agent, we clearly see that the two elements of change are distinct ; variability is in some manner excited, but it is the will of man which accumulates the variations in certain directions ; and it is this latter agency which answers to the survival...
Стр. 9 - ... free access to it from other countries be circumscribed, and let the change of conditions continue progressing (forming new stations), in such a case the original inhabitants must cease to be as perfectly adapted to the changed conditions as they were originally. It has been shown in a former part of this work, that such changes of external conditions would, from their acting on the reproductive system, probably cause the organization of those beings which were most affected to become, as under...
Стр. 32 - FLOWER in the crannied wall, I pluck you out of the crannies, I hold you here, root and all, in my hand, Little flower — but if I could understand What you are, root and all, and all in all, I should know what God and man is.
Стр. 22 - Thus, as I believe, natural selection will tend in the long run to reduce any part of the organisation, as soon as it becomes, through changed habits, superfluous, without by any means causing some other part to be largely developed in a corresponding degree. And, conversely, that natural selection may perfectly well succeed in largely developing...
Стр. 10 - ... trees, which has seeds that must be transported by certain birds, and which has flowers with separate sexes absolutely requiring the agency of certain insects to bring pollen from one flower to the other, it is equally preposterous to account for the structure of this parasite, with its relations to several distinct organic beings, by the effects of external conditions, or of habit, or of the volition of the plant itself.
Стр. 10 - Naturalists continually refer to external conditions, such as climate, food, &c., as the only possible cause of variation. In one limited sense, as we shall hereafter see, this may be true ; but it is preposterous to attribute to mere external conditions, the structure, for instance, of the woodpecker, with its feet, tail, beak, and tongue, so admirably adapted to catch insects under the bark of trees.
Стр. 6 - This wonderful relationship in the same continent between the dead and the living, will, I do not doubt, hereafter throw more light on the appearance of organic beings on our earth and their disappearance from it than any other class of facts.