On the Origin of Species by Means of Natural Selection: Or The Preservation of Favoured Races in the Struggle for LifeHumphrey Milford, Oxford University Press, 1923 - 454 páginas |
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Página 60
... fertility of these animals or plants has been suddenly and temporarily increased in any sensible degree . The obvious explanation is that the conditions of life have been very favourable , and that there has consequently been less ...
... fertility of these animals or plants has been suddenly and temporarily increased in any sensible degree . The obvious explanation is that the conditions of life have been very favourable , and that there has consequently been less ...
Página 70
... fertile , will beat the others and so yield more seed , and consequently in a few years quite supplant the other varieties . To keep up a mixed stock of even such extremely close varieties as the variously coloured sweet - peas , they ...
... fertile , will beat the others and so yield more seed , and consequently in a few years quite supplant the other varieties . To keep up a mixed stock of even such extremely close varieties as the variously coloured sweet - peas , they ...
Página 86
... fertility of clover depends on bees visiting and moving parts of the corolla , so as to push the pollen on to the stigmatic surface . Hence , again , if humble - bees were to become rare in any country , it might be a great advantage to ...
... fertility of clover depends on bees visiting and moving parts of the corolla , so as to push the pollen on to the stigmatic surface . Hence , again , if humble - bees were to become rare in any country , it might be a great advantage to ...
Página 88
... fertility to the offspring ; and on the other hand , that close interbreeding diminishes vigour and fertility ; that these facts alone incline me to believe that it is a general law of nature ( utterly ignorant though we be of the ...
... fertility to the offspring ; and on the other hand , that close interbreeding diminishes vigour and fertility ; that these facts alone incline me to believe that it is a general law of nature ( utterly ignorant though we be of the ...
Página 94
... fertility over the offspring from long - continued self - fertilisation , that they will have a better chance of surviving and propagating their kind ; and thus , in the long run , the influence of intercrosses , even at rare intervals ...
... fertility over the offspring from long - continued self - fertilisation , that they will have a better chance of surviving and propagating their kind ; and thus , in the long run , the influence of intercrosses , even at rare intervals ...
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Términos y frases comunes
accumulated adapted affinities allied species America amount analogous ancient appear Archipelago become bees believe birds breeds cause cells characters cirripedes climate closely allied colour common parent continuous crossed crustaceans degree difficulty distinct species divergence doubt embryo endemic Europe existing exterminated extinct extremely facts favourable fertility flowers formations forms fossil Gärtner genera genus geological geological period Glacial period gradations greater number groups of species habits Hence hermaphrodites hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossing land larvæ less living male mammals manner Marsupials migration modification modified descendants natural selection naturalists nearly nest oceanic islands offspring organisation perfect pigeons pistil plants pollen present principle probably produced progenitor ranked reciprocal crosses remarked resemble rock-pigeon rudimentary organs seeds sexual selection Silurian slight South America sterility structure struggle successive suppose swimbladder tend theory tion trees variability variation vary whole widely