The Origin of Species · Chapter
Nature of the Checks to Increase explained
Darwin explores the complex and often obscure checks that limit the natural tendency of each species to increase, including the roles of climate, food supply, predation, disease, and competition.
What happens
Darwin explores the complex and often obscure checks that limit the natural tendency of each species to increase, including the roles of climate, food supply, predation, disease, and competition. He emphasizes that climate often acts indirectly by favoring other species, and that the struggle for existence is most severe between individuals of the same or different species that rely on the same resources. He also notes the importance of a large population for a species' preservation and the role of intercrossing versus close interbreeding.
Themes in this chapter
Natural Selection and the Struggle for Existence
Darwin discusses the struggle for existence as a primary check on population increase, including competition for food and space, predation, and the indirect effects of climate.
Extinction and the Succession of Forms
The chapter examines how species decrease in numbers and disappear due to competition and environmental changes, linking to the process of extinction.
Key passages
“The causes which check the natural tendency of each species to increase are most obscure.”
The factors that limit the natural growth of every species are very difficult to understand.
Darwin acknowledges the complexity and mystery of population checks.
“Climate plays an important part in determining the average numbers of a species, and periodical seasons of extreme cold or drought seem to be the most effective of all checks.”
Climate significantly influences average population sizes, with extreme cold or drought being the most powerful limiting factors.
Highlights the role of climate as a direct and indirect check on species numbers.
“When we travel from south to north, or from a damp region to a dry, we invariably see some species gradually getting rarer and rarer, and finally disappearing; and the change of climate being conspicuous, we are tempted to attribute the whole effect to its direct action. But this is a false view; we forget that each species, even where it most abounds, is constantly suffering enormous destruction at some period of its life, from enemies or from competitors for the same place and food.”
When moving from south to north or from wet to dry areas, species become rarer and vanish; we often blame climate directly, but we overlook that even abundant species face massive destruction from enemies and competitors.
Darwin warns against oversimplifying the role of climate, emphasizing indirect effects through competition and predation.