Because he was well aware of the effect his theory of evolution would have on the public and on the Church of England, Darwin delayed publishing his work for several decades while he gathered additional evidence. After invoking selective breeding of domesticated species as evidence that groups of organisms are capable of change, he then proposed that natural populations can change as well. On which two lines of evidence did he base this proposal? a) Individuals within a population vary, yet island species around the world all appear to be related to each other. b) Organisms produce more offspring than can be supported by their environment, and adaptations to specific environments increase an organism's ability to survive and reproduce. c) Organisms within a population vary, and all populations produce more offspring than can be supported by the environment, resulting in competition for survival within the population. d) Some individuals leave more descendants than other individuals, but the individuals in a population are essentially identical to each other. e) Some individuals within a population have greater success in survival and reproduction than others, and favorable traits within a population will accumulate over generations.