What is the social category that developed during the 19th century of european imperialism?

Social Darwinism is a term for the collective ideas or policies that emerged during the 19th century. During 19th century, European countries were expanding their empire. This lead to the colonization of Asia and Africa. Racism has been rampant at that time. 

an early twentieth-century ad for model home blueprints

b europeans take corn to africa. corn becomes an important crop there.