Download Chapter 3: Struggle for Existence 1. Although scientists now

Chapter 3: Struggle for Existence
1. Although scientists now understand that selection can work in many different ways,
Darwin spends a lot of time in Chapter 3 discussing only one force of natural selection.
What does Darwin identify as this primary force of natural selection and how does he
describe it?
2. On page 66 Darwin writes, “Lighten any check, mitigate the destruction ever so little,
and the number of the species will almost instantaneously increase to any amount.” What
does he mean by “checks” and what are some examples he describes?
3. Darwin discusses introduced species in this chapter and provides several examples of
how introduced species often flourish in their new environment. What are “introduced
species” and why does he provide these examples in a chapter about competition? How
does the observation that “introduced species” are often successful in new environments
support his argument about the significance of competition in natural selection?
Chapter 4:
1. In Chapter 4, Darwin formally presents his theory of natural selection. In doing so, he
identifies environmental and biological conditions that are necessary for natural selection
to work. What are these conditions? (hint: some are summaries of ideas presented in
previous chapters.)
2. On page 87 Darwin states, “What natural selection cannot do, is modify the structure
of one species, without giving it any advantage, for the good of another species.” Do you
think this statement is accurate? Why might nature not be able to work this way?
3. Darwin recognizes the importance of sexual selection and its impact on evolution in
Chapter 4 (pg 87). What are the similarities and differences between natural selection
and sexual selection identified by Darwin?
4. Darwin discusses the importance of geographic isolation (e.g. islands) in natural
selection (pg 104). How is geographic isolation a factor in natural selection? Can you
think of any examples illustrating his point?
5. The only figure in the entire book is introduced in this chapter (pg 116, figure at end of
book). What is the figure and what points does it illustrate? How can it be used to
describe evolutionary theories?