Darwin's Four Postulates
by Arturo Ancira García
Darwin specified the fact that there will always be a surplus of variation within a species. This could involve differences in the DNA or in the genotype itself.
Because of the ways genes are carried through generations, Darwin specified that genes would be inherited by the organism offspring. This could be a good thing, (implying a good gene is passed on) or a bad thing, (when a bad recessive gene is passed on)
The external conditions in which an organism lives can apply pressure for an organism to adapt to its environment, strive and pass on its precious gene. In a nutshell, this postulate means that external conditions can affect survival.
Because the natural designs involved only the best traits surviving (survival of the fittest), evolution does not allow the bad traits to be passed on. That is, those who are not the most skillful organisms of a species do not get the privilege to pass on their gene. In general, the traits that are not suited for survival will not be passed on.