On the origin of species by means of natural selection ; or, The preservation of favored races in the struggle for lifeD. Appleton and Company, 1875 - 458페이지 |
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88개의 결과 중 1 - 5개
vii 페이지
... insects - Summary -205-234 CHAPTER IX . HYBRIDISM . Distinction between the sterility of first crosses and of hybrids Sterility various in degree , not universal , affected by close interbreeding , re- moved by domestication - Laws ...
... insects - Summary -205-234 CHAPTER IX . HYBRIDISM . Distinction between the sterility of first crosses and of hybrids Sterility various in degree , not universal , affected by close interbreeding , re- moved by domestication - Laws ...
2 페이지
... insects under the bark of trees . In the case of the mistletoe , which draws its nourishment from certain trees , which has seeds that must be transported by certain birds , and which has flowers with separate sexes absolutely requiring ...
... insects under the bark of trees . In the case of the mistletoe , which draws its nourishment from certain trees , which has seeds that must be transported by certain birds , and which has flowers with separate sexes absolutely requiring ...
35 페이지
... insects are far from uniform . Authors sometimes argue in a circle when they state that important organs never vary ; for these same authors practically rank those parts as important ( as some few naturalists have honestly confessed ) ...
... insects are far from uniform . Authors sometimes argue in a circle when they state that important organs never vary ; for these same authors practically rank those parts as important ( as some few naturalists have honestly confessed ) ...
37 페이지
... insects in North America and Europe , which differ very slightly from each other , have been ranked by one eminent naturalist as undoubted species , and by another as varieties , or , as they are often called , geographical races ! Mr ...
... insects in North America and Europe , which differ very slightly from each other , have been ranked by one eminent naturalist as undoubted species , and by another as varieties , or , as they are often called , geographical races ! Mr ...
38 페이지
... insects which are charac- terized as varieties in Mr. Wollaston's admirable work , but which would certainly be ... insects live on one kind of plant or on one group of plants ; some feed indiscriminately on many kinds , but do not in ...
... insects which are charac- terized as varieties in Mr. Wollaston's admirable work , but which would certainly be ... insects live on one kind of plant or on one group of plants ; some feed indiscriminately on many kinds , but do not in ...
자주 나오는 단어 및 구문
adapted admit affinities allied species America analogous ancient appear beak become bees believe belonging birds breeds cause cells characters climate closely allied colour continued crossed crustaceans degree developed difficulty distinct species doubt effects eggs embryo existing extinct extremely facts favourable fertilised fertility flowers formations formerly forms fossil Fritz Müller genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hybrids important individuals inhabitants inherited insects instance instincts intercrossing intermediate kind lamellæ larvæ less living male mammals manner Marsupials migration modified descendants natural selection naturalists nearly nest occasionally occur oceanic islands offspring organisation organs parent peculiar perfect pigeon pistil pollen present principle probably produced quadrupeds ranked reciprocal crosses remarked reproductive resemblance rudimentary seeds sexual selection Silurian slight South America stamens sterility structure struggle successive supposed theory tion variability variations varieties vary whilst whole wings young
인기 인용구
50 페이지 - I should premise that I use this term in a large and metaphorical sense, including dependence of one being on another, and including (which is more important) not only the life of the individual, but success in leaving progeny.
63 페이지 - It has been said that I speak of natural selection as an active power or Deity; but who objects to an author speaking of the attraction of gravity as ruling the movements of the planets ? Every one knows what is meant and is implied by such metaphorical expressions; and they are almost necessary for brevity.
65 페이지 - Can we wonder, then, that Nature's productions should be far " truer " in character than man's productions ; that they should be infinitely better adapted to the most complex conditions of life, and should plainly bear the stamp of far higher workmanship...
143 페이지 - 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 possible degree.
3 페이지 - As many more individuals of each species are born than can possibly survive ; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected.
56 페이지 - ... there was a large and extremely barren heath, which had never been touched by the hand of man ; but several hundred acres of exactly the same nature had been enclosed twenty-five years previously and planted with Scotch fir. The change in the native vegetation of the planted part of the heath was most remarkable, more than is generally seen in passing from one quite different soil to another ; not only the proportional numbers of the heath-plants were wholly changed, but twelve species of plants...
49 페이지 - Nothing is easier than to admit in words the truth of the universal struggle for life, or more difficult — at least I have found it so — than constantly to bear this conclusion in mind. Yet unless it be thoroughly engrained in the mind, the whole economy of nature, with every fact on distribution, rarity, abundance, extinction, and variation, will be dimly seen or quite misunderstood.
48 페이지 - ... we see beautiful adaptations everywhere and in every part of the organic world.
69 페이지 - The result is not death to the unsuccessful competitor but few or no offspring. Sexual selection is, therefore, less rigorous than natural selection. Generally the most vigorous males, those which are best fitted for their places in nature, will leave most progeny. But in many cases victory depends not so much on general vigor as on having special weapons, confined to the male sex. A hornless stag or spurless cock would have a poor chance of leaving numerous offspring.
412 페이지 - What limit can be put to this power, acting during long ages and rigidly scrutinising the whole constitution, structure, and habits of each creature, — favouring the good and rejecting the bad ? I can see no limit to this power, in slowly and beautifully adapting each form to the most complex relations of life.