TF: Pan Pan Jiang
T HEO RIGIN OF THE SPECIES:C HAPTER 4(N ATURAL S ELECTION )
What does Darwinargueisnecessary fornatural selection towork?
Darwin argues that natural selection requires heritable variation and a struggle for survival in order to
take place. He states that changing environmental conditions allows the greatest potential for
evolutionary change. Darwin also points out that population size is important because the more
individuals there are, the greater the chances that favorable variations will arise.
What arethe similarities anddifferencethatDarwinnotesbetween natural selectionand sexual selection?
Darwin notes that sexual selection is less severe than natural selection: the losing male, although he
survives, will produce few or no offspring. He also observes that victors are not necessarily more fit in
terms of survival, but are better adapted to win at competing for females (versus natural selection,
being better adapted for survival). Darwin makes the case that sexual selection is a relatively weak
factor compared to natural selection, even as he posits that female selection could influence male