“as many more individuals are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected.” this quote is an excerpt from which of the following written works?

an essay on the principle of population

the wealth of nations

the communist manifesto

on the origin of species