Effect of struggle for existence under unchanged conditions--The effect under change of conditions--Divergence of character--In insects--In birds--In mammalia--Divergence leads to a maximum of life in each area--Closely allied species inhabit distinct areas--Adaptation to conditions at various periods of life--The continued existence of low forms of life--Extinction of low types among the higher animals--Circumstances favourable to the origin of new species--Probable origin of the dippers--The importance of isolation--On the advance of organisation by natural selection--Summary of the first five chapters
CHAPTER V · NATURAL SELECTION BY VARIATION AND SURVIVAL OF THE FITTEST
From Darwinism: An Exposition of the Theory of Natural Selection by Alfred Russel Wallace.
