The Origin of Species
Charles DarwinSözler ve Alıntılar
It may metaphorically be said that natural selection is daily and hourly scrutinising, throughout the world, the slightest variations; rejecting those that are bad, preserving and adding up all that are good; silently and insensibly working, WHENEVER AND WHEREVER OPPORTUNITY OFFERS, at the improvement of each organic being in relation to its organic and inorganic conditions of life.
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your habits get into your genetics.
Changed habits produce an inherited effect, as in the period of the flowering of plants when transported from one climate to another.
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The carrier, more especially the male bird, is also remarkable from the wonderful development of the carunculated skin about the head, and this is accompanied by greatly elongated eyelids, very large external orifices to the nostrils, and a wide gape of mouth. The short-faced tumbler has a beak in outline almost like that of a finch; and the common tumbler has the singular inherited habit of flying at a great height in a compact flock, and tumbling in the air head over heels.
Isolation also is an important element in the modification of species through natural selection. In a confined or isolated area, if not very large, the organic and inorganic conditions of life will generally be almost uniform; so that natural selection will tend to modify all the varying individuals of the same species in the same manner.
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privilege of parthenogenesis
I must here introduce a short digression. In the case of animals and plants with separated sexes, it is of course obvious that two individuals must always (with the exception of the curious and not well understood cases of parthenogenesis) unite for each birth; but in the case of hermaphrodites this is far from obvious.
Domestic races often have a somewhat monstrous character; by which I mean, that, although differing from each other, and from other species of the same genus, in several trifling respects, they often differ in an extreme
degree in some one part, both when compared one with another, and more especially when compared with the species under nature to which they are nearest allied.
don't attribute everything to sexual reproduction.
Some naturalists have maintained that all variations are connected with the act of sexual reproduction; but this is certainly an error; for I have given in another work a long list of "sporting plants," as they are called by gardeners;that is, of plants which have suddenly produced a single budwith a new and sometimes widely different character from that of the other buds on the same plant.
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