Problem : What are the five main ideas contained in Darwin's theory of evolution?

The five main ideas, as distinguished by biologist Ernst Mayr are evolution as such, common decent, gradualism, population speciation, and natural selection.

Problem : How was Darwin's view of the "struggle for life" different from that of previous scientists?

Scientists before Darwin thought that competition or "struggle for life" might be the reason for the survival or extinction of species. Darwin felt that such a struggle might also occur between the members of a species, determining which individuals survived and reproduced and which did not.

Problem : According to Darwin's view of population speciation, how would giraffes develop long necks?

According to Darwin, some giraffes would randomly be born with long necks. They would be able to pass this trait on to their offspring, and this hereditary trait would gradually spread throughout the population

Problem : On what five postulates does natural selection depend?

Natural selection depends on these five postulates: a)individuals are variable; b)some variations are passed down; c)more offspring are produced than can survive; d)survival and reproduction are not random; and e)the history of earth is long.