On the Origin of Species

Darwin outlines the motivation and scope of his theory of species origins.

Examines how domestic animals and plants vary under human-controlled conditions, demonstrating selection's power.

Demonstrates that species in nature vary and that common species show more variation than rare ones.

Explains how organisms compete for survival and resources, creating selective pressures on populations.

Presents the theory of natural selection as the primary mechanism for species modification and adaptation.

Discusses the principles governing variation including use, disuse, correlation of growth, and inheritance patterns.

Addresses objections to natural selection including complex organs, transitional forms, and perfect adaptations.

Examines how instincts can be acquired and modified through natural selection, using bee and ant examples.

Analyzes sterility of hybrids versus fertility of varieties when crossed, supporting the theory.

Explains classification, homologous organs, and embryological characters through descent with modification.

Summarizes evidence for descent with modification and discusses future implications for natural history.