Quote: slight differences lead to differences in survival and new species; an altered environment can exterminate varieties and parents of varieties

Quotation

Most or perhaps all the variations from the typical form of a species must have some definite effect, however slight, on the habits or capacities of the individuals. Even a change of colour might, by rendering them more or less distinguishable, affect their safety; a greater or less development of hair might modify their habits. ... It is also evident that most changes would affect, either favourably or adversely, the powers of prolonging existence. ...[If] any species should produce a variety having slightly increased powers of preserving existence, that variety must inevitably in time acquire a superiority in numbers. ... [p. 332] Now, let some alteration of physical conditions occur in the district--a long period of draught, a destruction of vegetation by locusts, the irruption of some new carnivorous animal seeking "pastures new"--any change in fact tending to render existence more difficult to the species in question, and tasking its utmost powers to avoid complete extermination.; it is evident that, of all the individuals composing the species, those forming the least numerous and most feebly organized variety would suffer first, and, were the pressure severe, must soon become extinct. The same causes continuing in action, the parent species would next suffer ... [and] might also become extinct. The superior variety would then alone remain ... The variety would now have replaced the species, of which it would be a more perfectly developed and more highly organized form. ... Such a variety could not return to the original form; for that form is an inferior one, and could never compete with it for existence.   Google-1   Google-2

Published before 1923

Additional Titles

Quote: a new species can not revert to the original form; the original can not compete with the new

Related Topics

Topic: evolutionary systems (38 items)