Species that struggle to adapt to survive will become extinct.

Hence it is quite credible that the presence of a feline animal in large numbers in a district might determine, through the intervention first of mice and then of bees, the frequency of certain flowers in that district!

In the long history of humankind (and animal kind, too) those who learned to collaborate and improvise most effectively have prevailed.

If numerous species, belonging to the same genera or families, have really started into life all at once, the fact would be fatal to the theory of descent with slow modification through natural selection.

Though nature grants vast periods of time for the work of natural selection, she does not grant an indefinite period; for as all organic beings are striving, it may be said, to seize on each place in the economy of nature, if any one species does not become modified and improved in a corresponding degree with its competitors, it will soon be exterminated.

Natural Selection almost inevitably causes much Extinction of the less improved forms of life and induces what I have called Divergence of Character.