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On the Origin of Species

Struggle For Existence
Its bearing on natural selection -- The term used in a wide sense -- Geometrical ratio of
increase -- Rapid increase of naturalised animals and plants -- Nature of the checks to
increase -- Competition universal -- Effects of climate -- Protection from the number of
individuals -- Complex relations of all animals and plants throughout nature -- Struggle
for life most severe between individuals and varieties of the same species: often severe
between species of the same genus -- The relation of organism to organism the most
important of all relations.
Before entering on the subject of this chapter I must make a few preliminary remarks to
show how the struggle for existence bears on natural selection. It has been seen in the last
chapter that among organic beings in a state of nature there is some individual variability:
indeed I am not aware that this has ever been disputed. It is immaterial for us whether a
multitude of doubtful forms be called species or sub-species or varieties; what rank, for
instance, the two or three hundred doubtful forms of British plants are entitled to hold, if
the existence of any well-marked varieties be admitted. But the mere existence of
individual variability and of some few well-marked varieties, though necessary as the
foundation for the work, helps us but little in understanding how species arise in nature.
How have all those exquisite adaptations of one part of the organisation to another part,
and to the conditions of life and of one organic being to another being, been perfected?
We see these beautiful co-adaptations most plainly in the woodpecker and the mistletoe;
and only a little less plainly in the humblest parasite which clings to the hairs of a
quadruped or feathers of a bird; in the structure of the beetle which dives through the
water; in the plumed seed which is wafted by the gentlest breeze; in short, we see
beautiful adaptations everywhere and in every part of the organic world.
Again, it may be asked, how is it that varieties, which I have called incipient species,
become ultimately converted into good and distinct species, which in most cases
obviously differ from each other far more than do the varieties of the same species? How
do those groups of species, which constitute what are called distinct genera and which
differ from each other more than do the species of the same genus, arise? All these
results, as we shall more fully see in the next chapter, follow from the struggle for life.
Owing to this struggle, variations, however slight and from whatever cause proceeding, if
they be in any degree profitable to the individuals of a species, in their infinitely complex
relations to other organic beings and to their physical conditions of life, will tend to the
preservation of such individuals, and will generally be inherited by the offspring. The
offspring, also, will thus have a better chance of surviving, for, of the many individuals of
any species which are periodically born, but a small number can survive. I have called
this principle, by which each slight variation, if useful, is preserved, by the term natural
selection, in order to mark its relation to man's power of selection. But the expression
often used by Mr. Herbert Spencer, of the Survival of the Fittest, is more accurate, and is
sometimes equally convenient. We have seen that man by selection can certainly produce
great results, and can adapt organic beings to his own uses, through the accumulation of
slight but useful variations, given to him by the hand of Nature. But Natural Selection, we
 
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